diff --git a/src-tauri/src/commands/java2lce/block_mapping.rs b/src-tauri/src/commands/java2lce/block_mapping.rs
new file mode 100644
index 0000000..cee48fc
--- /dev/null
+++ b/src-tauri/src/commands/java2lce/block_mapping.rs
@@ -0,0 +1,1353 @@
+use std::collections::HashMap;
+use super::nbt::NbtCompound;
+#[derive(Clone, Copy, Default)]
+pub struct LegacyBlockState {
+    pub id: u8,
+    pub data: u8,
+}
+
+pub fn map_modern_block_state(compound: &NbtCompound) -> LegacyBlockState {
+    map_modern_block_state_inner(compound, None)
+}
+
+pub fn map_modern_block_state_with_context(
+    compound: &NbtCompound,
+    unknown_blocks: Option<&mut Vec<String>>,
+) -> LegacyBlockState {
+    map_modern_block_state_inner(compound, unknown_blocks)
+}
+
+fn map_modern_block_state_inner(
+    compound: &NbtCompound,
+    mut unknown_blocks: Option<&mut Vec<String>>,
+) -> LegacyBlockState {
+    let name_raw = compound.string("Name").unwrap_or("minecraft:air");
+    let name = name_raw.strip_prefix("minecraft:").unwrap_or(name_raw);
+    let properties = compound.compound("Properties");
+    if let Some(fluid) = try_map_fluid(name, properties) {
+        return fluid;
+    }
+    if let Some(slab) = try_map_slab(name, properties) {
+        return slab;
+    }
+    if let Some(directional) = try_map_directional(name, properties) {
+        return directional;
+    }
+    if let Some(flattened) = try_map_flattened_colored(name) {
+        return flattened;
+    }
+    if let Some(direct) = MODERN_DIRECT_MAP.get(name) {
+        return *direct;
+    }
+    if let Some(colored) = try_map_colored(name, properties) {
+        return colored;
+    }
+    if let Some(wood) = try_map_wood(name, properties) {
+        return wood;
+    }
+    if let Some(variant) = try_map_variant(name, properties) {
+        return variant;
+    }
+
+    if let Some(ref mut blocks) = unknown_blocks {
+        if !name.is_empty() && name != "air" && name != "cave_air" && name != "void_air" {
+            blocks.push(name.to_string());
+        }
+    }
+
+    LegacyBlockState { id: 0, data: 0 }
+}
+
+fn get_property<'a>(properties: Option<&'a NbtCompound>, name: &str) -> String {
+    properties
+        .and_then(|p| p.string(name))
+        .unwrap_or("")
+        .to_string()
+}
+
+fn get_bool_property(properties: Option<&NbtCompound>, name: &str) -> bool {
+    get_property(properties, name).to_lowercase() == "true"
+}
+
+fn get_int_property(properties: Option<&NbtCompound>, name: &str, default: i32) -> i32 {
+    get_property(properties, name)
+        .parse()
+        .unwrap_or(default)
+}
+
+fn try_map_fluid(name: &str, properties: Option<&NbtCompound>) -> Option<LegacyBlockState> {
+    if name != "water" && name != "lava" {
+        return None;
+    }
+    let level = get_int_property(properties, "level", 0).clamp(0, 15);
+    let is_source = level == 0;
+    let data = level as u8;
+    Some(if name == "water" {
+        LegacyBlockState {
+            id: if is_source { 9 } else { 8 },
+            data,
+        }
+    } else {
+        LegacyBlockState {
+            id: if is_source { 11 } else { 10 },
+            data,
+        }
+    })
+}
+
+fn try_map_directional(name: &str, properties: Option<&NbtCompound>) -> Option<LegacyBlockState> {
+    match name {
+        "ladder" => Some(LegacyBlockState {
+            id: 65,
+            data: map_ladder_facing(&get_property(properties, "facing")),
+        }),
+        "vine" => Some(LegacyBlockState {
+            id: 106,
+            data: map_vine_faces(properties),
+        }),
+        "lever" => {
+            let mut data =
+                map_lever_data(&get_property(properties, "face"), &get_property(properties, "facing"));
+            if get_bool_property(properties, "powered") {
+                data |= 8;
+            }
+            Some(LegacyBlockState { id: 69, data })
+        }
+        _ if name.ends_with("_button") => {
+            let id = if is_wood_family(name) { 143 } else { 77 };
+            let mut data = map_button_facing(&get_property(properties, "facing"));
+            if get_bool_property(properties, "powered") {
+                data |= 8;
+            }
+            Some(LegacyBlockState { id, data })
+        }
+        _ if name.ends_with("_fence_gate") => {
+            let mut data = map_fence_gate_facing(&get_property(properties, "facing"));
+            if get_bool_property(properties, "open") {
+                data |= 4;
+            }
+            Some(LegacyBlockState { id: 107, data })
+        }
+        _ if name.ends_with("_pressure_plate") => {
+            let id = match name {
+                "light_weighted_pressure_plate" => 147,
+                "heavy_weighted_pressure_plate" => 148,
+                _ if is_wood_family(name) => 72,
+                _ => 70,
+            };
+            let powered =
+                get_bool_property(properties, "powered") || get_int_property(properties, "power", 0) > 0;
+            Some(LegacyBlockState {
+                id,
+                data: if powered { 1 } else { 0 },
+            })
+        }
+        _ if name.ends_with("_door") || name == "iron_door" => {
+            let id = if name == "iron_door" { 71 } else { 64 };
+            let half = get_property(properties, "half");
+            let is_upper = half == "upper";
+            if is_upper {
+                let mut data = 8;
+                if get_property(properties, "hinge") == "right" {
+                    data |= 1;
+                }
+                if get_bool_property(properties, "powered") {
+                    data |= 2;
+                }
+                Some(LegacyBlockState { id, data })
+            } else {
+                let mut data = map_door_facing(&get_property(properties, "facing"));
+                if get_bool_property(properties, "open") {
+                    data |= 4;
+                }
+                Some(LegacyBlockState { id, data })
+            }
+        }
+        _ if try_get_stairs_id(name).is_some() => {
+            let id = try_get_stairs_id(name).unwrap();
+            let mut data = map_stairs_facing(&get_property(properties, "facing"));
+            if get_property(properties, "half") == "top" {
+                data |= 4;
+            }
+            Some(LegacyBlockState { id, data })
+        }
+        _ if name.ends_with("trapdoor") => {
+            let mut data = map_trapdoor_facing(&get_property(properties, "facing"));
+            if get_bool_property(properties, "open") {
+                data |= 4;
+            }
+            if get_property(properties, "half") == "top" {
+                data |= 8;
+            }
+            Some(LegacyBlockState { id: 96, data })
+        }
+        "dispenser" | "dropper" => {
+            let id = if name == "dropper" { 158 } else { 23 };
+            let mut data = map_facing_data(&get_property(properties, "facing"));
+            if get_bool_property(properties, "triggered") {
+                data |= 8;
+            }
+            Some(LegacyBlockState { id, data })
+        }
+        "piston" | "sticky_piston" => {
+            let id = if name == "sticky_piston" { 29 } else { 33 };
+            let mut data = map_facing_data(&get_property(properties, "facing"));
+            if get_bool_property(properties, "extended") {
+                data |= 8;
+            }
+            Some(LegacyBlockState { id, data })
+        }
+        "piston_head" => {
+            let mut data = map_facing_data(&get_property(properties, "facing"));
+            if get_property(properties, "type") == "sticky" {
+                data |= 8;
+            }
+            Some(LegacyBlockState { id: 34, data })
+        }
+        "redstone_wire" => {
+            let data = get_int_property(properties, "power", 0).clamp(0, 15) as u8;
+            Some(LegacyBlockState { id: 55, data })
+        }
+        "repeater" => {
+            let id = if get_bool_property(properties, "powered") { 94 } else { 93 };
+            let dir = map_repeater_direction(&get_property(properties, "facing"));
+            let delay = get_int_property(properties, "delay", 1).clamp(1, 4);
+            Some(LegacyBlockState {
+                id,
+                data: dir | (((delay - 1) as u8) << 2),
+            })
+        }
+        "comparator" => {
+            let id = if get_bool_property(properties, "powered") { 150 } else { 149 };
+            let dir = map_repeater_direction(&get_property(properties, "facing"));
+            let mode = if get_property(properties, "mode") == "subtract" { 4 } else { 0 };
+            Some(LegacyBlockState {
+                id,
+                data: dir | mode,
+            })
+        }
+        "wall_torch" => Some(LegacyBlockState {
+            id: 50,
+            data: map_wall_torch_facing(&get_property(properties, "facing")),
+        }),
+        "redstone_wall_torch" => {
+            let id = if get_bool_property(properties, "lit") { 76 } else { 75 };
+            Some(LegacyBlockState {
+                id,
+                data: map_wall_torch_facing(&get_property(properties, "facing")),
+            })
+        }
+        "nether_wart" => Some(LegacyBlockState {
+            id: 115,
+            data: get_int_property(properties, "age", 0).clamp(0, 3) as u8,
+        }),
+        "wheat" => Some(LegacyBlockState {
+            id: 59,
+            data: get_int_property(properties, "age", 0).clamp(0, 7) as u8,
+        }),
+        "pumpkin_stem" | "attached_pumpkin_stem" => Some(LegacyBlockState {
+            id: 104,
+            data: if name == "attached_pumpkin_stem" {
+                7
+            } else {
+                get_int_property(properties, "age", 0).clamp(0, 7) as u8
+            },
+        }),
+        "melon_stem" | "attached_melon_stem" => Some(LegacyBlockState {
+            id: 105,
+            data: if name == "attached_melon_stem" {
+                7
+            } else {
+                get_int_property(properties, "age", 0).clamp(0, 7) as u8
+            },
+        }),
+        "cocoa" => {
+            let age = get_int_property(properties, "age", 0).clamp(0, 2) as u8;
+            let dir = map_repeater_direction(&get_property(properties, "facing"));
+            Some(LegacyBlockState {
+                id: 127,
+                data: (age << 2) | dir,
+            })
+        }
+        "hay_block" => Some(LegacyBlockState {
+            id: 170,
+            data: match get_property(properties, "axis").as_str() {
+                "x" => 4,
+                "z" => 8,
+                _ => 0,
+            },
+        }),
+        "quartz_pillar" => Some(LegacyBlockState {
+            id: 155,
+            data: match get_property(properties, "axis").as_str() {
+                "x" => 3,
+                "z" => 4,
+                _ => 2,
+            },
+        }),
+        "nether_portal" => Some(LegacyBlockState {
+            id: 90,
+            data: if get_property(properties, "axis") == "z" { 2 } else { 1 },
+        }),
+        _ => None,
+    }
+}
+
+fn try_map_slab(name: &str, properties: Option<&NbtCompound>) -> Option<LegacyBlockState> {
+    if !name.ends_with("_slab") {
+        return None;
+    }
+
+    let slab_type = get_property(properties, "type");
+    let is_top = slab_type == "top";
+    let is_double = slab_type == "double";
+    if let Some(wood_variant) = get_wood_slab_variant(name) {
+        return Some(if is_double {
+            LegacyBlockState {
+                id: 125,
+                data: wood_variant,
+            }
+        } else {
+            LegacyBlockState {
+                id: 126,
+                data: wood_variant | if is_top { 8 } else { 0 },
+            }
+        });
+    }
+
+    if let Some(slab_variant) = get_stone_slab_variant(name) {
+        return Some(if is_double {
+            LegacyBlockState {
+                id: 43,
+                data: slab_variant,
+            }
+        } else {
+            LegacyBlockState {
+                id: 44,
+                data: slab_variant | if is_top { 8 } else { 0 },
+            }
+        });
+    }
+
+    Some(if is_double {
+        LegacyBlockState { id: 43, data: 0 }
+    } else {
+        LegacyBlockState {
+            id: 44,
+            data: if is_top { 8 } else { 0 },
+        }
+    })
+}
+
+fn get_wood_slab_variant(name: &str) -> Option<u8> {
+    match name {
+        "oak_slab" => Some(0),
+        "spruce_slab" => Some(1),
+        "birch_slab" => Some(2),
+        "jungle_slab" => Some(3),
+        "acacia_slab" => Some(4),
+        "dark_oak_slab" => Some(5),
+        _ => None,
+    }
+}
+
+fn get_stone_slab_variant(name: &str) -> Option<u8> {
+    match name {
+        "stone_slab" | "smooth_stone_slab" | "andesite_slab" | "polished_andesite_slab"
+        | "diorite_slab" | "polished_diorite_slab" | "granite_slab" | "polished_granite_slab" => {
+            Some(0)
+        }
+        "sandstone_slab" | "smooth_sandstone_slab" | "cut_sandstone_slab"
+        | "red_sandstone_slab" | "smooth_red_sandstone_slab" | "cut_red_sandstone_slab" => Some(1),
+        "cobblestone_slab" | "mossy_cobblestone_slab" | "cobbled_deepslate_slab"
+        | "deepslate_brick_slab" | "deepslate_tile_slab" => Some(3),
+        "brick_slab" => Some(4),
+        "stone_brick_slab" | "mossy_stone_brick_slab" => Some(5),
+        "nether_brick_slab" | "red_nether_brick_slab" => Some(6),
+        "quartz_slab" | "smooth_quartz_slab" | "purpur_slab" | "prismarine_slab"
+        | "prismarine_brick_slab" | "dark_prismarine_slab" => Some(7),
+        _ => None,
+    }
+}
+
+fn try_get_stairs_id(name: &str) -> Option<u8> {
+    match name {
+        "oak_stairs" | "spruce_stairs" | "birch_stairs" | "jungle_stairs" | "acacia_stairs"
+        | "dark_oak_stairs" => Some(53),
+        "cobblestone_stairs" | "stone_stairs" | "mossy_cobblestone_stairs"
+        | "cobbled_deepslate_stairs" | "blackstone_stairs" => Some(67),
+        "brick_stairs" => Some(108),
+        "stone_brick_stairs" | "dark_prismarine_stairs" | "prismarine_stairs"
+        | "prismarine_brick_stairs" | "polished_blackstone_brick_stairs"
+        | "mossy_stone_brick_stairs" | "deepslate_brick_stairs" | "deepslate_tile_stairs" => {
+            Some(109)
+        }
+        "nether_brick_stairs" | "crimson_stairs" | "warped_stairs" => Some(114),
+        "sandstone_stairs" | "red_sandstone_stairs" => Some(128),
+        "quartz_stairs" | "purpur_stairs" => Some(156),
+        "spruce_stairs" => Some(134),
+        "birch_stairs" => Some(135),
+        "jungle_stairs" => Some(136),
+        "acacia_stairs" => Some(163),
+        "dark_oak_stairs" => Some(164),
+        _ => None,
+    }
+}
+
+fn map_stairs_facing(facing: &str) -> u8 {
+    match facing {
+        "east" => 0,
+        "west" => 1,
+        "south" => 2,
+        "north" => 3,
+        _ => 0,
+    }
+}
+
+fn map_ladder_facing(facing: &str) -> u8 {
+    match facing {
+        "north" => 2,
+        "south" => 3,
+        "west" => 4,
+        "east" => 5,
+        _ => 2,
+    }
+}
+
+fn map_button_facing(facing: &str) -> u8 {
+    match facing {
+        "east" => 1,
+        "west" => 2,
+        "south" => 3,
+        "north" => 4,
+        _ => 1,
+    }
+}
+
+fn map_fence_gate_facing(facing: &str) -> u8 {
+    match facing {
+        "south" => 0,
+        "west" => 1,
+        "north" => 2,
+        "east" => 3,
+        _ => 0,
+    }
+}
+
+fn map_vine_faces(properties: Option<&NbtCompound>) -> u8 {
+    let mut data = 0;
+    if get_bool_property(properties, "south") {
+        data |= 1;
+    }
+    if get_bool_property(properties, "west") {
+        data |= 2;
+    }
+    if get_bool_property(properties, "north") {
+        data |= 4;
+    }
+    if get_bool_property(properties, "east") {
+        data |= 8;
+    }
+    data
+}
+
+fn map_lever_data(face: &str, facing: &str) -> u8 {
+    match face {
+        "floor" => {
+            if facing == "east" || facing == "west" {
+                6
+            } else {
+                5
+            }
+        }
+        "ceiling" => {
+            if facing == "east" || facing == "west" {
+                7
+            } else {
+                0
+            }
+        }
+        _ => map_button_facing(facing),
+    }
+}
+
+fn map_door_facing(facing: &str) -> u8 {
+    match facing {
+        "east" => 0,
+        "south" => 1,
+        "west" => 2,
+        "north" => 3,
+        _ => 0,
+    }
+}
+
+fn map_trapdoor_facing(facing: &str) -> u8 {
+    match facing {
+        "north" => 0,
+        "south" => 1,
+        "west" => 2,
+        "east" => 3,
+        _ => 0,
+    }
+}
+
+fn map_facing_data(facing: &str) -> u8 {
+    match facing {
+        "down" => 0,
+        "up" => 1,
+        "north" => 2,
+        "south" => 3,
+        "west" => 4,
+        "east" => 5,
+        _ => 3,
+    }
+}
+
+fn map_repeater_direction(facing: &str) -> u8 {
+    match facing {
+        "south" => 0,
+        "west" => 1,
+        "north" => 2,
+        "east" => 3,
+        _ => 0,
+    }
+}
+
+fn map_wall_torch_facing(facing: &str) -> u8 {
+    match facing {
+        "east" => 1,
+        "west" => 2,
+        "south" => 3,
+        "north" => 4,
+        _ => 1,
+    }
+}
+
+fn try_map_colored(name: &str, properties: Option<&NbtCompound>) -> Option<LegacyBlockState> {
+    let color = get_color_data(&get_property(properties, "color"));
+    match name {
+        "wool" => Some(LegacyBlockState { id: 35, data: color }),
+        "stained_glass" => Some(LegacyBlockState { id: 95, data: color }),
+        "stained_glass_pane" => Some(LegacyBlockState { id: 160, data: color }),
+        "stained_hardened_clay" | "terracotta" => {
+            Some(LegacyBlockState { id: 159, data: color })
+        }
+        "concrete" => Some(LegacyBlockState {
+            id: 172,
+            data: color,
+        }),
+        "concrete_powder" => Some(LegacyBlockState { id: 12, data: color }),
+        "glazed_terracotta" => Some(LegacyBlockState { id: 159, data: color }),
+        _ => None,
+    }
+}
+
+fn try_map_flattened_colored(name: &str) -> Option<LegacyBlockState> {
+    let (color_data, suffix) = split_color_prefix(name)?;
+    let data = color_data;
+    match suffix.as_str() {
+        "wool" => Some(LegacyBlockState { id: 35, data }),
+        "stained_glass" | "glass" => Some(LegacyBlockState { id: 95, data }),
+        "stained_glass_pane" | "glass_pane" => Some(LegacyBlockState { id: 160, data }),
+        "stained_hardened_clay" | "terracotta" => Some(LegacyBlockState { id: 159, data }),
+        "concrete" => Some(LegacyBlockState { id: 172, data }),
+        "concrete_powder" => Some(LegacyBlockState { id: 12, data }),
+        "glazed_terracotta" => Some(LegacyBlockState { id: 159, data }),
+        "carpet" => Some(LegacyBlockState { id: 171, data }),
+        _ => None,
+    }
+}
+
+fn split_color_prefix(name: &str) -> Option<(u8, String)> {
+    for color_name in COLOR_NAMES {
+        let prefix = format!("{}_", color_name);
+        if name.starts_with(&prefix) {
+            let suffix = name[prefix.len()..].to_string();
+            return Some((get_color_data(color_name), suffix));
+        }
+    }
+    None
+}
+
+const COLOR_NAMES: &[&str] = &[
+    "white", "orange", "magenta", "light_blue", "yellow", "lime", "pink", "gray", "silver",
+    "light_gray", "cyan", "purple", "blue", "brown", "green", "red", "black",
+];
+
+fn get_color_data(color: &str) -> u8 {
+    match color {
+        "white" => 0,
+        "orange" => 1,
+        "magenta" => 2,
+        "light_blue" => 3,
+        "yellow" => 4,
+        "lime" => 5,
+        "pink" => 6,
+        "gray" => 7,
+        "light_gray" => 8,
+        "cyan" => 9,
+        "purple" => 10,
+        "blue" => 11,
+        "brown" => 12,
+        "green" => 13,
+        "red" => 14,
+        "black" => 15,
+        _ => 0,
+    }
+}
+
+fn try_map_wood(name: &str, properties: Option<&NbtCompound>) -> Option<LegacyBlockState> {
+    let wood_type = get_property(properties, "variant");
+    let wood_type = if wood_type.is_empty() {
+        get_prefix_before_underscore(name)
+    } else {
+        wood_type
+    };
+
+    let data_value = match wood_type.as_str() {
+        "spruce" => 1,
+        "birch" => 2,
+        "jungle" => 3,
+        "acacia" => 0,
+        "dark_oak" => 1,
+        _ => 0,
+    };
+
+    if name.ends_with("_planks") || name == "planks" {
+        return Some(LegacyBlockState { id: 5, data: data_value });
+    }
+    if name.ends_with("_sapling") || name == "sapling" {
+        return Some(LegacyBlockState { id: 6, data: data_value });
+    }
+    if name.ends_with("_log") || name == "log" {
+        return Some(LegacyBlockState {
+            id: 17,
+            data: data_value.min(3),
+        });
+    }
+    if name.ends_with("_leaves") || name == "leaves" {
+        return Some(LegacyBlockState {
+            id: 18,
+            data: data_value.min(3),
+        });
+    }
+    if name.ends_with("_stairs") && name.contains("wood") {
+        return Some(LegacyBlockState { id: 53, data: 0 });
+    }
+    if name.ends_with("_door") {
+        return Some(LegacyBlockState { id: 64, data: 0 });
+    }
+    if name.ends_with("_fence") {
+        return Some(LegacyBlockState { id: 85, data: 0 });
+    }
+    if name.ends_with("_fence_gate") {
+        return Some(LegacyBlockState { id: 107, data: 0 });
+    }
+    if name.ends_with("_pressure_plate") && is_wood_family(name) {
+        return Some(LegacyBlockState { id: 72, data: 0 });
+    }
+
+    None
+}
+
+fn try_map_variant(name: &str, properties: Option<&NbtCompound>) -> Option<LegacyBlockState> {
+    if let Some(fallback) = try_map_common_fallback(name, properties) {
+        return Some(fallback);
+    }
+
+    if name == "redstone_lamp" {
+        let lit = get_bool_property(properties, "lit");
+        return Some(LegacyBlockState {
+            id: if lit { 124 } else { 123 },
+            data: 0,
+        });
+    }
+
+    let result = match name {
+        "deepslate" | "polished_deepslate" | "tuff" | "calcite" | "dripstone_block" => {
+            Some(LegacyBlockState { id: 1, data: 0 })
+        }
+        "cobbled_deepslate" => Some(LegacyBlockState { id: 4, data: 0 }),
+        "deepslate_bricks" | "deepslate_tiles" => Some(LegacyBlockState { id: 98, data: 0 }),
+        "cracked_deepslate_bricks" | "cracked_deepslate_tiles" => {
+            Some(LegacyBlockState { id: 98, data: 2 })
+        }
+        "chiseled_deepslate" => Some(LegacyBlockState { id: 98, data: 3 }),
+        "deepslate_coal_ore" => Some(LegacyBlockState { id: 16, data: 0 }),
+        "deepslate_iron_ore" | "deepslate_copper_ore" => {
+            Some(LegacyBlockState { id: 15, data: 0 })
+        }
+        "deepslate_gold_ore" => Some(LegacyBlockState { id: 14, data: 0 }),
+        "deepslate_redstone_ore" => Some(LegacyBlockState { id: 73, data: 0 }),
+        "deepslate_lapis_ore" => Some(LegacyBlockState { id: 21, data: 0 }),
+        "deepslate_diamond_ore" => Some(LegacyBlockState { id: 56, data: 0 }),
+        "deepslate_emerald_ore" => Some(LegacyBlockState { id: 129, data: 0 }),
+        "deepslate_tile_stairs" | "deepslate_brick_stairs" | "cobbled_deepslate_stairs" => {
+            Some(LegacyBlockState { id: 67, data: 0 })
+        }
+        "deepslate_tile_slab" | "deepslate_brick_slab" | "cobbled_deepslate_slab" => {
+            Some(LegacyBlockState { id: 44, data: 3 })
+        }
+        "deepslate_tile_wall" | "deepslate_brick_wall" | "cobbled_deepslate_wall" => {
+            Some(LegacyBlockState { id: 139, data: 0 })
+        }
+        "grass_block" => Some(LegacyBlockState { id: 2, data: 0 }),
+        "coarse_dirt" | "podzol" => Some(LegacyBlockState { id: 3, data: 0 }),
+        "grass_path" | "dirt_path" | "moss_carpet" => Some(LegacyBlockState { id: 2, data: 0 }),
+        "cobblestone_wall" => Some(LegacyBlockState { id: 139, data: 0 }),
+        "mossy_cobblestone_wall" => Some(LegacyBlockState { id: 139, data: 1 }),
+        "smooth_stone_slab" => Some(LegacyBlockState { id: 44, data: 0 }),
+        "stone_brick_stairs" => Some(LegacyBlockState { id: 109, data: 0 }),
+        "mossy_stone_bricks" => Some(LegacyBlockState { id: 98, data: 1 }),
+        "cracked_stone_bricks" => Some(LegacyBlockState { id: 98, data: 2 }),
+        "chiseled_stone_bricks" => Some(LegacyBlockState { id: 98, data: 3 }),
+        "red_sand" => Some(LegacyBlockState { id: 12, data: 1 }),
+        "red_sandstone" => Some(LegacyBlockState { id: 24, data: 0 }),
+        "smooth_sandstone" => Some(LegacyBlockState { id: 24, data: 2 }),
+        "chiseled_sandstone" | "cut_sandstone" => Some(LegacyBlockState { id: 24, data: 1 }),
+        "smooth_red_sandstone" | "chiseled_red_sandstone" | "cut_red_sandstone" => {
+            Some(LegacyBlockState { id: 24, data: 0 })
+        }
+        "red_sandstone_stairs" => Some(LegacyBlockState { id: 128, data: 0 }),
+        "red_sandstone_slab" => Some(LegacyBlockState { id: 44, data: 1 }),
+        "prismarine" | "prismarine_bricks" | "dark_prismarine" => {
+            Some(LegacyBlockState { id: 1, data: 0 })
+        }
+        "sea_lantern" => Some(LegacyBlockState { id: 89, data: 0 }),
+        "purpur_block" | "purpur_pillar" => Some(LegacyBlockState { id: 155, data: 0 }),
+        "purpur_stairs" => Some(LegacyBlockState { id: 156, data: 0 }),
+        "purpur_slab" => Some(LegacyBlockState { id: 44, data: 0 }),
+        "end_stone_bricks" => Some(LegacyBlockState { id: 121, data: 0 }),
+        "magma_block" => Some(LegacyBlockState { id: 87, data: 0 }),
+        "nether_wart_block" | "red_nether_bricks" => Some(LegacyBlockState { id: 112, data: 0 }),
+        "bone_block" => Some(LegacyBlockState { id: 1, data: 0 }),
+        "packed_ice" | "blue_ice" => Some(LegacyBlockState { id: 79, data: 0 }),
+        "observer" | "beetroots" | "kelp" | "kelp_plant" | "seagrass" | "tall_seagrass"
+        | "coral_block" | "tube_coral_block" | "brain_coral_block" | "bubble_coral_block"
+        | "fire_coral_block" | "horn_coral_block" | "end_rod" | "chorus_plant"
+        | "chorus_flower" | "end_gateway" | "structure_void" => {
+            Some(LegacyBlockState { id: 0, data: 0 })
+        }
+        "sunflower" | "lilac" | "rose_bush" | "peony" => {
+            if get_property(properties, "half") == "upper" {
+                Some(LegacyBlockState { id: 0, data: 0 })
+            } else {
+                Some(LegacyBlockState { id: 38, data: 0 })
+            }
+        }
+        "tall_grass" => {
+            if get_property(properties, "half") == "upper" {
+                Some(LegacyBlockState { id: 0, data: 0 })
+            } else {
+                let grass_type = get_property(properties, "type");
+                Some(LegacyBlockState {
+                    id: 31,
+                    data: if grass_type == "fern" { 2 } else { 1 },
+                })
+            }
+        }
+        "large_fern" => {
+            if get_property(properties, "half") == "upper" {
+                Some(LegacyBlockState { id: 0, data: 0 })
+            } else {
+                Some(LegacyBlockState { id: 31, data: 2 })
+            }
+        }
+        "stone" => {
+            let _type = get_property(properties, "type");
+            Some(LegacyBlockState { id: 1, data: 0 })
+        }
+        "sandstone" => {
+            let stype = get_property(properties, "type");
+            Some(LegacyBlockState {
+                id: 24,
+                data: match stype.as_str() {
+                    "chiseled" => 1,
+                    "smooth" => 2,
+                    _ => 0,
+                },
+            })
+        }
+        "stone_bricks" => {
+            let stype = get_property(properties, "type");
+            Some(LegacyBlockState {
+                id: 98,
+                data: match stype.as_str() {
+                    "mossy" => 1,
+                    "cracked" => 2,
+                    "chiseled" => 3,
+                    _ => 0,
+                },
+            })
+        }
+        _ => None,
+    };
+
+    result
+}
+
+fn try_map_common_fallback(name: &str, properties: Option<&NbtCompound>) -> Option<LegacyBlockState> {
+    if name.ends_with("_button") {
+        return Some(LegacyBlockState {
+            id: if is_wood_family(name) { 143 } else { 77 },
+            data: 0,
+        });
+    }
+    if name.ends_with("_wall_sign") {
+        return Some(LegacyBlockState {
+            id: 68,
+            data: map_wall_sign_facing(&get_property(properties, "facing")),
+        });
+    }
+    if name.ends_with("_sign") {
+        return Some(LegacyBlockState {
+            id: 63,
+            data: (get_int_property(properties, "rotation", 0) & 0x0F) as u8,
+        });
+    }
+    if name.ends_with("_wall") {
+        return Some(LegacyBlockState { id: 139, data: 0 });
+    }
+    if name.ends_with("_bed") {
+        let mut data = map_bed_facing(&get_property(properties, "facing"));
+        if get_property(properties, "part") == "head" {
+            data |= 8;
+        }
+        return Some(LegacyBlockState { id: 26, data });
+    }
+    if name.ends_with("_banner") {
+        return Some(LegacyBlockState { id: 0, data: 0 });
+    }
+
+    match name {
+        "barrier" | "structure_void" => Some(LegacyBlockState { id: 0, data: 0 }),
+        "bamboo" => Some(LegacyBlockState { id: 83, data: 0 }),
+        "cake" => Some(LegacyBlockState { id: 92, data: 0 }),
+        "brewing_stand" => Some(LegacyBlockState { id: 117, data: 0 }),
+        "barrel" => Some(LegacyBlockState { id: 54, data: 0 }),
+        "blast_furnace" => Some(LegacyBlockState { id: 61, data: 0 }),
+        "campfire" => Some(LegacyBlockState { id: 50, data: 0 }),
+        "azure_bluet" | "blue_orchid" => Some(LegacyBlockState { id: 38, data: 0 }),
+        "attached_melon_stem" => Some(LegacyBlockState { id: 105, data: 7 }),
+        "attached_pumpkin_stem" => Some(LegacyBlockState { id: 104, data: 7 }),
+        "andesite" | "diorite" | "granite" | "polished_andesite" | "polished_diorite"
+        | "polished_granite" => Some(LegacyBlockState { id: 1, data: 0 }),
+        "andesite_stairs" | "diorite_stairs" | "granite_stairs" | "polished_andesite_stairs"
+        | "polished_diorite_stairs" | "polished_granite_stairs" => {
+            Some(LegacyBlockState { id: 109, data: 0 })
+        }
+        "bubble_column" => Some(LegacyBlockState { id: 9, data: 0 }),
+        "amethyst_block" | "budding_amethyst" | "amethyst_cluster" => {
+            Some(LegacyBlockState { id: 20, data: 0 })
+        }
+        _ => None,
+    }
+}
+
+fn map_bed_facing(facing: &str) -> u8 {
+    match facing {
+        "south" => 0,
+        "west" => 1,
+        "north" => 2,
+        "east" => 3,
+        _ => 0,
+    }
+}
+
+fn map_wall_sign_facing(facing: &str) -> u8 {
+    match facing {
+        "north" => 2,
+        "south" => 3,
+        "west" => 4,
+        "east" => 5,
+        _ => 2,
+    }
+}
+
+fn get_prefix_before_underscore(value: &str) -> String {
+    let index = value.find('_');
+    match index {
+        Some(i) if i > 0 => value[..i].to_string(),
+        _ => value.to_string(),
+    }
+}
+
+fn is_wood_family(name: &str) -> bool {
+    name.contains("oak")
+        || name.contains("spruce")
+        || name.contains("birch")
+        || name.contains("jungle")
+        || name.contains("acacia")
+        || name.contains("dark_oak")
+        || name.contains("mangrove")
+        || name.contains("cherry")
+        || name.contains("bamboo")
+        || name.contains("crimson")
+        || name.contains("warped")
+}
+
+pub fn is_valid_lce_tile_id(id: u8) -> bool {
+    id <= 160 || (id >= 170 && id <= 173)
+}
+
+pub fn remap_blocks(blocks: &mut [u8], _data: &mut [u8]) {
+    for id in blocks.iter_mut() {
+        let mut bid = *id;
+        if bid == 137 {
+            bid = 1;
+        }
+        if bid >= 165 {
+            if let Some(&replacement) = BLOCK_REMAP_TABLE.get(&bid) {
+                bid = replacement;
+            }
+        }
+        if !is_valid_lce_tile_id(bid) {
+            bid = 0;
+        }
+        *id = bid;
+    }
+}
+
+static MODERN_DIRECT_MAP: once_cell::sync::Lazy<HashMap<&'static str, LegacyBlockState>> =
+    once_cell::sync::Lazy::new(|| {
+        let mut m = HashMap::new();
+        m.insert("air", LegacyBlockState { id: 0, data: 0 });
+        m.insert("cave_air", LegacyBlockState { id: 0, data: 0 });
+        m.insert("void_air", LegacyBlockState { id: 0, data: 0 });
+        m.insert("stone", LegacyBlockState { id: 1, data: 0 });
+        m.insert("grass", LegacyBlockState { id: 31, data: 1 });
+        m.insert("short_grass", LegacyBlockState { id: 31, data: 1 });
+        m.insert("short_dry_grass", LegacyBlockState { id: 31, data: 1 });
+        m.insert("dirt", LegacyBlockState { id: 3, data: 0 });
+        m.insert("cobblestone", LegacyBlockState { id: 4, data: 0 });
+        m.insert("bedrock", LegacyBlockState { id: 7, data: 0 });
+        m.insert("water", LegacyBlockState { id: 8, data: 0 });
+        m.insert("lava", LegacyBlockState { id: 10, data: 0 });
+        m.insert("sand", LegacyBlockState { id: 12, data: 0 });
+        m.insert("gravel", LegacyBlockState { id: 13, data: 0 });
+        m.insert("gold_ore", LegacyBlockState { id: 14, data: 0 });
+        m.insert("iron_ore", LegacyBlockState { id: 15, data: 0 });
+        m.insert("coal_ore", LegacyBlockState { id: 16, data: 0 });
+        m.insert("oak_log", LegacyBlockState { id: 17, data: 0 });
+        m.insert("oak_leaves", LegacyBlockState { id: 18, data: 0 });
+        m.insert("glass", LegacyBlockState { id: 20, data: 0 });
+        m.insert("lapis_ore", LegacyBlockState { id: 21, data: 0 });
+        m.insert("lapis_block", LegacyBlockState { id: 22, data: 0 });
+        m.insert("dispenser", LegacyBlockState { id: 23, data: 0 });
+        m.insert("sandstone", LegacyBlockState { id: 24, data: 0 });
+        m.insert("note_block", LegacyBlockState { id: 25, data: 0 });
+        m.insert("powered_rail", LegacyBlockState { id: 27, data: 0 });
+        m.insert("detector_rail", LegacyBlockState { id: 28, data: 0 });
+        m.insert("sticky_piston", LegacyBlockState { id: 29, data: 0 });
+        m.insert("cobweb", LegacyBlockState { id: 30, data: 0 });
+        m.insert("dead_bush", LegacyBlockState { id: 32, data: 0 });
+        m.insert("piston", LegacyBlockState { id: 33, data: 0 });
+        m.insert("wool", LegacyBlockState { id: 35, data: 0 });
+        m.insert("dandelion", LegacyBlockState { id: 37, data: 0 });
+        m.insert("poppy", LegacyBlockState { id: 38, data: 0 });
+        m.insert("brown_mushroom", LegacyBlockState { id: 39, data: 0 });
+        m.insert("red_mushroom", LegacyBlockState { id: 40, data: 0 });
+        m.insert("gold_block", LegacyBlockState { id: 41, data: 0 });
+        m.insert("iron_block", LegacyBlockState { id: 42, data: 0 });
+        m.insert("stone_slab", LegacyBlockState { id: 44, data: 0 });
+        m.insert("bricks", LegacyBlockState { id: 45, data: 0 });
+        m.insert("tnt", LegacyBlockState { id: 46, data: 0 });
+        m.insert("bookshelf", LegacyBlockState { id: 47, data: 0 });
+        m.insert("mossy_cobblestone", LegacyBlockState { id: 48, data: 0 });
+        m.insert("obsidian", LegacyBlockState { id: 49, data: 0 });
+        m.insert("torch", LegacyBlockState { id: 50, data: 0 });
+        m.insert("fire", LegacyBlockState { id: 51, data: 0 });
+        m.insert("mob_spawner", LegacyBlockState { id: 52, data: 0 });
+        m.insert("oak_stairs", LegacyBlockState { id: 53, data: 0 });
+        m.insert("chest", LegacyBlockState { id: 54, data: 0 });
+        m.insert("diamond_ore", LegacyBlockState { id: 56, data: 0 });
+        m.insert("diamond_block", LegacyBlockState { id: 57, data: 0 });
+        m.insert("crafting_table", LegacyBlockState { id: 58, data: 0 });
+        m.insert("farmland", LegacyBlockState { id: 60, data: 0 });
+        m.insert("furnace", LegacyBlockState { id: 61, data: 0 });
+        m.insert("ladder", LegacyBlockState { id: 65, data: 0 });
+        m.insert("rail", LegacyBlockState { id: 66, data: 0 });
+        m.insert("lever", LegacyBlockState { id: 69, data: 0 });
+        m.insert("stone_pressure_plate", LegacyBlockState { id: 70, data: 0 });
+        m.insert("oak_pressure_plate", LegacyBlockState { id: 72, data: 0 });
+        m.insert("redstone_ore", LegacyBlockState { id: 73, data: 0 });
+        m.insert("redstone_torch", LegacyBlockState { id: 76, data: 0 });
+        m.insert("stone_button", LegacyBlockState { id: 77, data: 0 });
+        m.insert("snow", LegacyBlockState { id: 78, data: 0 });
+        m.insert("ice", LegacyBlockState { id: 79, data: 0 });
+        m.insert("snow_block", LegacyBlockState { id: 80, data: 0 });
+        m.insert("cactus", LegacyBlockState { id: 81, data: 0 });
+        m.insert("clay", LegacyBlockState { id: 82, data: 0 });
+        m.insert("jukebox", LegacyBlockState { id: 84, data: 0 });
+        m.insert("oak_fence", LegacyBlockState { id: 85, data: 0 });
+        m.insert("netherrack", LegacyBlockState { id: 87, data: 0 });
+        m.insert("soul_sand", LegacyBlockState { id: 88, data: 0 });
+        m.insert("glowstone", LegacyBlockState { id: 89, data: 0 });
+        m.insert("jack_o_lantern", LegacyBlockState { id: 91, data: 0 });
+        m.insert("stone_bricks", LegacyBlockState { id: 98, data: 0 });
+        m.insert("brown_mushroom_block", LegacyBlockState { id: 99, data: 0 });
+        m.insert("red_mushroom_block", LegacyBlockState { id: 100, data: 0 });
+        m.insert("iron_bars", LegacyBlockState { id: 101, data: 0 });
+        m.insert("glass_pane", LegacyBlockState { id: 102, data: 0 });
+        m.insert("melon", LegacyBlockState { id: 103, data: 0 });
+        m.insert("vine", LegacyBlockState { id: 106, data: 0 });
+        m.insert("oak_fence_gate", LegacyBlockState { id: 107, data: 0 });
+        m.insert("brick_stairs", LegacyBlockState { id: 108, data: 0 });
+        m.insert("stone_brick_stairs", LegacyBlockState { id: 109, data: 0 });
+        m.insert("mycelium", LegacyBlockState { id: 110, data: 0 });
+        m.insert("lily_pad", LegacyBlockState { id: 111, data: 0 });
+        m.insert("nether_bricks", LegacyBlockState { id: 112, data: 0 });
+        m.insert("nether_brick_fence", LegacyBlockState { id: 113, data: 0 });
+        m.insert("nether_brick_stairs", LegacyBlockState { id: 114, data: 0 });
+        m.insert("enchanting_table", LegacyBlockState { id: 116, data: 0 });
+        m.insert("end_stone", LegacyBlockState { id: 121, data: 0 });
+        m.insert("sandstone_stairs", LegacyBlockState { id: 128, data: 0 });
+        m.insert("emerald_ore", LegacyBlockState { id: 129, data: 0 });
+        m.insert("ender_chest", LegacyBlockState { id: 130, data: 0 });
+        m.insert("tripwire_hook", LegacyBlockState { id: 131, data: 0 });
+        m.insert("emerald_block", LegacyBlockState { id: 133, data: 0 });
+        m.insert("spruce_stairs", LegacyBlockState { id: 134, data: 0 });
+        m.insert("birch_stairs", LegacyBlockState { id: 135, data: 0 });
+        m.insert("jungle_stairs", LegacyBlockState { id: 136, data: 0 });
+        m.insert("command_block", LegacyBlockState { id: 1, data: 0 });
+        m.insert("beacon", LegacyBlockState { id: 138, data: 0 });
+        m.insert("cobblestone_wall", LegacyBlockState { id: 139, data: 0 });
+        m.insert("flower_pot", LegacyBlockState { id: 140, data: 0 });
+        m.insert("carrots", LegacyBlockState { id: 141, data: 0 });
+        m.insert("potatoes", LegacyBlockState { id: 142, data: 0 });
+        m.insert("oak_button", LegacyBlockState { id: 143, data: 0 });
+        m.insert("anvil", LegacyBlockState { id: 145, data: 0 });
+        m.insert("trapped_chest", LegacyBlockState { id: 146, data: 0 });
+        m.insert("light_weighted_pressure_plate", LegacyBlockState { id: 147, data: 0 });
+        m.insert("heavy_weighted_pressure_plate", LegacyBlockState { id: 148, data: 0 });
+        m.insert("daylight_detector", LegacyBlockState { id: 151, data: 0 });
+        m.insert("redstone_block", LegacyBlockState { id: 152, data: 0 });
+        m.insert("quartz_ore", LegacyBlockState { id: 153, data: 0 });
+        m.insert("hopper", LegacyBlockState { id: 154, data: 0 });
+        m.insert("quartz_block", LegacyBlockState { id: 155, data: 0 });
+        m.insert("quartz_stairs", LegacyBlockState { id: 156, data: 0 });
+        m.insert("activator_rail", LegacyBlockState { id: 157, data: 0 });
+        m.insert("dropper", LegacyBlockState { id: 158, data: 0 });
+        m.insert("stained_hardened_clay", LegacyBlockState { id: 159, data: 0 });
+        m.insert("stained_glass", LegacyBlockState { id: 95, data: 0 });
+        m.insert("stained_glass_pane", LegacyBlockState { id: 160, data: 0 });
+        m.insert("leaves2", LegacyBlockState { id: 161, data: 0 });
+        m.insert("log2", LegacyBlockState { id: 162, data: 0 });
+        m.insert("acacia_stairs", LegacyBlockState { id: 163, data: 0 });
+        m.insert("dark_oak_stairs", LegacyBlockState { id: 164, data: 0 });
+        m.insert("fern", LegacyBlockState { id: 31, data: 2 });
+        m.insert("sugar_cane", LegacyBlockState { id: 83, data: 0 });
+        m.insert("pumpkin", LegacyBlockState { id: 86, data: 0 });
+        m.insert("carved_pumpkin", LegacyBlockState { id: 86, data: 0 });
+        m.insert("nether_quartz_ore", LegacyBlockState { id: 153, data: 0 });
+        m.insert("dragon_egg", LegacyBlockState { id: 122, data: 0 });
+        m.insert("spawner", LegacyBlockState { id: 52, data: 0 });
+        m.insert("tripwire", LegacyBlockState { id: 132, data: 0 });
+        m.insert("sponge", LegacyBlockState { id: 19, data: 0 });
+        m.insert("wet_sponge", LegacyBlockState { id: 19, data: 0 });
+        m.insert("cauldron", LegacyBlockState { id: 118, data: 0 });
+        m.insert("water_cauldron", LegacyBlockState { id: 118, data: 3 });
+        m.insert("coal_block", LegacyBlockState { id: 173, data: 0 });
+        m.insert("mushroom_stem", LegacyBlockState { id: 99, data: 10 });
+        m.insert("smooth_stone", LegacyBlockState { id: 1, data: 0 });
+        m.insert("infested_stone", LegacyBlockState { id: 1, data: 0 });
+        m.insert("infested_stone_bricks", LegacyBlockState { id: 98, data: 0 });
+        m.insert("infested_deepslate", LegacyBlockState { id: 1, data: 0 });
+        m.insert(
+            "polished_blackstone_bricks",
+            LegacyBlockState { id: 98, data: 0 },
+        );
+        m.insert(
+            "cracked_polished_blackstone_bricks",
+            LegacyBlockState { id: 98, data: 2 },
+        );
+        m.insert("blackstone", LegacyBlockState { id: 4, data: 0 });
+        m.insert("quartz_bricks", LegacyBlockState { id: 155, data: 0 });
+        m.insert(
+            "chiseled_quartz_block",
+            LegacyBlockState { id: 155, data: 1 },
+        );
+        m.insert(
+            "chiseled_nether_bricks",
+            LegacyBlockState { id: 112, data: 0 },
+        );
+        m.insert("smooth_basalt", LegacyBlockState { id: 1, data: 0 });
+        m.insert("pointed_dripstone", LegacyBlockState { id: 1, data: 0 });
+        m.insert("lodestone", LegacyBlockState { id: 1, data: 0 });
+        m.insert("structure_block", LegacyBlockState { id: 1, data: 0 });
+        m.insert("stonecutter", LegacyBlockState { id: 4, data: 0 });
+        m.insert("rooted_dirt", LegacyBlockState { id: 3, data: 0 });
+        m.insert("moss_block", LegacyBlockState { id: 48, data: 0 });
+        m.insert(
+            "dried_kelp_block",
+            LegacyBlockState { id: 170, data: 0 },
+        );
+        m.insert("crimson_stem", LegacyBlockState { id: 17, data: 0 });
+        m.insert("warped_stem", LegacyBlockState { id: 17, data: 0 });
+        m.insert(
+            "stripped_crimson_stem",
+            LegacyBlockState { id: 17, data: 0 },
+        );
+        m.insert(
+            "stripped_warped_stem",
+            LegacyBlockState { id: 17, data: 0 },
+        );
+        m.insert("azalea", LegacyBlockState { id: 18, data: 0 });
+        m.insert("flowering_azalea", LegacyBlockState { id: 18, data: 0 });
+        m.insert(
+            "big_dripleaf",
+            LegacyBlockState { id: 111, data: 0 },
+        );
+        m.insert(
+            "big_dripleaf_stem",
+            LegacyBlockState { id: 17, data: 0 },
+        );
+        m.insert("small_dripleaf", LegacyBlockState { id: 0, data: 0 });
+        m.insert("hanging_roots", LegacyBlockState { id: 0, data: 0 });
+        m.insert("spore_blossom", LegacyBlockState { id: 38, data: 0 });
+        m.insert(
+            "twisting_vines",
+            LegacyBlockState { id: 106, data: 0 },
+        );
+        m.insert(
+            "twisting_vines_plant",
+            LegacyBlockState { id: 106, data: 0 },
+        );
+        m.insert("cave_vines", LegacyBlockState { id: 0, data: 0 });
+        m.insert(
+            "cave_vines_plant",
+            LegacyBlockState { id: 0, data: 0 },
+        );
+        m.insert("glow_lichen", LegacyBlockState { id: 0, data: 0 });
+        m.insert("cornflower", LegacyBlockState { id: 38, data: 0 });
+        m.insert(
+            "lily_of_the_valley",
+            LegacyBlockState { id: 38, data: 0 },
+        );
+        m.insert("oxeye_daisy", LegacyBlockState { id: 38, data: 0 });
+        m.insert("pink_tulip", LegacyBlockState { id: 38, data: 0 });
+        m.insert("brain_coral", LegacyBlockState { id: 38, data: 0 });
+        m.insert("bubble_coral", LegacyBlockState { id: 38, data: 0 });
+        m.insert("fire_coral", LegacyBlockState { id: 38, data: 0 });
+        m.insert("horn_coral", LegacyBlockState { id: 38, data: 0 });
+        m.insert("tube_coral", LegacyBlockState { id: 38, data: 0 });
+        m.insert(
+            "horn_coral_fan",
+            LegacyBlockState { id: 38, data: 0 },
+        );
+        m.insert(
+            "tube_coral_fan",
+            LegacyBlockState { id: 38, data: 0 },
+        );
+        m.insert("smoker", LegacyBlockState { id: 61, data: 0 });
+        m.insert(
+            "grindstone",
+            LegacyBlockState { id: 145, data: 0 },
+        );
+        m.insert("bell", LegacyBlockState { id: 145, data: 0 });
+        m.insert("loom", LegacyBlockState { id: 58, data: 0 });
+        m.insert(
+            "smithing_table",
+            LegacyBlockState { id: 58, data: 0 },
+        );
+        m.insert(
+            "target",
+            LegacyBlockState { id: 70, data: 0 },
+        );
+        m.insert("chain", LegacyBlockState { id: 101, data: 0 });
+        m.insert(
+            "lightning_rod",
+            LegacyBlockState { id: 101, data: 0 },
+        );
+        m.insert("lantern", LegacyBlockState { id: 50, data: 0 });
+        m.insert(
+            "shroomlight",
+            LegacyBlockState { id: 89, data: 0 },
+        );
+        m.insert(
+            "soul_campfire",
+            LegacyBlockState { id: 51, data: 0 },
+        );
+        m.insert(
+            "bee_nest",
+            LegacyBlockState { id: 54, data: 0 },
+        );
+        m.insert(
+            "wither_skeleton_skull",
+            LegacyBlockState { id: 144, data: 0 },
+        );
+        m.insert(
+            "dragon_wall_head",
+            LegacyBlockState { id: 144, data: 0 },
+        );
+        m.insert(
+            "nether_portal",
+            LegacyBlockState { id: 90, data: 0 },
+        );
+        m.insert(
+            "white_candle",
+            LegacyBlockState { id: 50, data: 0 },
+        );
+        m.insert(
+            "orange_candle",
+            LegacyBlockState { id: 50, data: 0 },
+        );
+        m.insert(
+            "gray_candle",
+            LegacyBlockState { id: 50, data: 0 },
+        );
+        m.insert(
+            "cyan_candle",
+            LegacyBlockState { id: 50, data: 0 },
+        );
+        m.insert(
+            "lime_candle",
+            LegacyBlockState { id: 50, data: 0 },
+        );
+        m.insert(
+            "potted_blue_orchid",
+            LegacyBlockState { id: 140, data: 0 },
+        );
+        m.insert(
+            "potted_brown_mushroom",
+            LegacyBlockState { id: 140, data: 0 },
+        );
+        m.insert(
+            "potted_cactus",
+            LegacyBlockState { id: 140, data: 0 },
+        );
+        m.insert(
+            "potted_dandelion",
+            LegacyBlockState { id: 140, data: 0 },
+        );
+        m.insert(
+            "potted_oxeye_daisy",
+            LegacyBlockState { id: 140, data: 0 },
+        );
+        m.insert(
+            "potted_poppy",
+            LegacyBlockState { id: 140, data: 0 },
+        );
+        m.insert(
+            "potted_red_mushroom",
+            LegacyBlockState { id: 140, data: 0 },
+        );
+        m.insert(
+            "powder_snow",
+            LegacyBlockState { id: 80, data: 0 },
+        );
+        m.insert(
+            "copper_ore",
+            LegacyBlockState { id: 15, data: 0 },
+        );
+        m.insert(
+            "oxidized_copper",
+            LegacyBlockState { id: 15, data: 0 },
+        );
+        m.insert(
+            "weathered_copper",
+            LegacyBlockState { id: 15, data: 0 },
+        );
+        m.insert(
+            "raw_copper_block",
+            LegacyBlockState { id: 42, data: 0 },
+        );
+        m.insert(
+            "raw_iron_block",
+            LegacyBlockState { id: 42, data: 0 },
+        );
+        m.insert(
+            "small_amethyst_bud",
+            LegacyBlockState { id: 20, data: 0 },
+        );
+        m.insert(
+            "medium_amethyst_bud",
+            LegacyBlockState { id: 20, data: 0 },
+        );
+        m.insert(
+            "large_amethyst_bud",
+            LegacyBlockState { id: 20, data: 0 },
+        );
+        m.insert(
+            "slime_block",
+            LegacyBlockState { id: 0, data: 0 },
+        );
+        m.insert("light", LegacyBlockState { id: 0, data: 0 });
+        m.insert(
+            "scaffolding",
+            LegacyBlockState { id: 0, data: 0 },
+        );
+        m.insert(
+            "powder_snow_cauldron",
+            LegacyBlockState { id: 118, data: 0 },
+        );
+        m.insert(
+            "lava_cauldron",
+            LegacyBlockState { id: 118, data: 0 },
+        );
+        m
+    });
+
+static BLOCK_REMAP_TABLE: once_cell::sync::Lazy<HashMap<u8, u8>> =
+    once_cell::sync::Lazy::new(|| {
+        let mut m = HashMap::new();
+        m.insert(174, 79);
+        m.insert(175, 0);
+        m.insert(165, 0);
+        m.insert(166, 0);
+        m.insert(167, 96);
+        m.insert(168, 1);
+        m.insert(169, 89);
+        m.insert(176, 0);
+        m.insert(177, 0);
+        m.insert(178, 151);
+        m.insert(179, 24);
+        m.insert(180, 128);
+        m.insert(181, 43);
+        m.insert(182, 44);
+        m.insert(183, 107);
+        m.insert(184, 107);
+        m.insert(185, 107);
+        m.insert(186, 107);
+        m.insert(187, 107);
+        m.insert(188, 85);
+        m.insert(189, 85);
+        m.insert(190, 85);
+        m.insert(191, 85);
+        m.insert(192, 85);
+        m.insert(193, 64);
+        m.insert(194, 64);
+        m.insert(195, 64);
+        m.insert(196, 64);
+        m.insert(197, 64);
+        m.insert(198, 0);
+        m.insert(199, 0);
+        m.insert(200, 0);
+        m.insert(201, 155);
+        m.insert(202, 155);
+        m.insert(203, 156);
+        m.insert(204, 43);
+        m.insert(205, 44);
+        m.insert(206, 121);
+        m.insert(207, 0);
+        m.insert(208, 2);
+        m.insert(209, 0);
+        m.insert(210, 1);
+        m.insert(211, 1);
+        m.insert(212, 79);
+        m.insert(213, 87);
+        m.insert(214, 112);
+        m.insert(215, 112);
+        m.insert(216, 1);
+        m.insert(217, 0);
+        m.insert(218, 0);
+        for i in 219..=234 {
+            m.insert(i, 0);
+        }
+        for i in 235..=250 {
+            m.insert(i, 159);
+        }
+        m.insert(251, 172);
+        m.insert(252, 12);
+        m
+    });
diff --git a/src-tauri/src/commands/java2lce/chunk.rs b/src-tauri/src/commands/java2lce/chunk.rs
new file mode 100644
index 0000000..e279b98
--- /dev/null
+++ b/src-tauri/src/commands/java2lce/chunk.rs
@@ -0,0 +1,1690 @@
+use std::collections::HashMap;
+use super::block_mapping::{self, LegacyBlockState};
+use super::nbt;
+use super::payload;
+const CHUNK_BLOCKS: usize = 65536;
+const CHUNK_NIBBLES: usize = 32768;
+const HEIGHTMAP_SIZE: usize = 256;
+const BIOMES_SIZE: usize = 256;
+const STAIR_UPSIDE_DOWN_BIT: u8 = 4;
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum JavaChunkFormat {
+    Unknown,
+    LegacyBlockArray,
+    LegacyAnvil,
+    ModernPalette,
+    ModernExtendedHeight,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub struct JavaChunkFormatInfo {
+    pub format: JavaChunkFormat,
+    pub has_level_wrapper: bool,
+    pub data_version: i32,
+    pub min_section_y: Option<i32>,
+    pub max_section_y: Option<i32>,
+    pub has_modern_entity_tags: bool,
+}
+
+impl JavaChunkFormatInfo {
+    pub fn is_section_based(&self) -> bool {
+        matches!(
+            self.format,
+            JavaChunkFormat::LegacyAnvil
+                | JavaChunkFormat::ModernPalette
+                | JavaChunkFormat::ModernExtendedHeight
+        )
+    }
+
+    pub fn uses_palette_sections(&self) -> bool {
+        matches!(
+            self.format,
+            JavaChunkFormat::ModernPalette | JavaChunkFormat::ModernExtendedHeight
+        )
+    }
+
+    pub fn uses_modern_content_schema(&self) -> bool {
+        self.uses_palette_sections() || self.has_modern_entity_tags
+    }
+
+    pub fn requires_section_shift(&self) -> bool {
+        self.format == JavaChunkFormat::ModernExtendedHeight
+    }
+}
+
+pub fn inspect_chunk(root_tag: &nbt::NbtCompound) -> JavaChunkFormatInfo {
+    let has_level_wrapper = root_tag.get("Level").is_some();
+    let source_level = root_tag
+        .compound("Level")
+        .unwrap_or(root_tag);
+
+    let data_version = root_tag
+        .int("DataVersion")
+        .or_else(|| {
+            root_tag
+                .compound("Level")
+                .and_then(|l| l.int("DataVersion"))
+        })
+        .unwrap_or(0);
+
+    let has_modern_entity_tags = source_level.contains("block_entities") || source_level.contains("entities");
+    let has_legacy_block_arrays = source_level.contains("Blocks");
+    let sections = source_level
+        .list("Sections")
+        .or_else(|| source_level.list("sections"));
+
+    let mut has_sections = false;
+    let mut has_palette_sections = false;
+    let mut min_section_y: Option<i32> = None;
+    let mut max_section_y: Option<i32> = None;
+    if let Some(sects) = sections {
+        has_sections = !sects.is_empty();
+        for tag in sects {
+            if let nbt::NbtValue::Compound(section) = tag {
+                if let Some(sy) = read_section_y(section) {
+                    min_section_y = Some(min_section_y.map_or(sy, |v| v.min(sy)));
+                    max_section_y = Some(max_section_y.map_or(sy, |v| v.max(sy)));
+                }
+                if section_uses_palette_storage(section) {
+                    has_palette_sections = true;
+                }
+            }
+        }
+    }
+
+    let format = if has_palette_sections {
+        let has_extended = min_section_y.map_or(false, |v| v < 0)
+            || max_section_y.map_or(false, |v| v > 15);
+        if has_extended {
+            JavaChunkFormat::ModernExtendedHeight
+        } else {
+            JavaChunkFormat::ModernPalette
+        }
+    } else if has_sections {
+        JavaChunkFormat::LegacyAnvil
+    } else if has_legacy_block_arrays {
+        JavaChunkFormat::LegacyBlockArray
+    } else {
+        JavaChunkFormat::Unknown
+    };
+
+    JavaChunkFormatInfo {
+        format,
+        has_level_wrapper,
+        data_version,
+        min_section_y,
+        max_section_y,
+        has_modern_entity_tags,
+    }
+}
+
+pub fn read_section_y(section: &nbt::NbtCompound) -> Option<i32> {
+    if let Some(b) = section.byte("Y") {
+        return Some(b as i8 as i32);
+    }
+    if let Some(i) = section.int("Y") {
+        return Some(i);
+    }
+    if let Some(s) = section.short("Y") {
+        return Some(s as i32);
+    }
+    None
+}
+
+fn section_uses_palette_storage(section: &nbt::NbtCompound) -> bool {
+    section.contains("block_states")
+        || section.contains("Palette")
+        || section.contains("BlockStates")
+}
+
+fn get_byte_array_or_default(compound: &nbt::NbtCompound, name: &str, default_size: usize) -> Vec<u8> {
+    match compound.byte_array(name) {
+        Some(bytes) => {
+            let mut v = bytes.to_vec();
+            if v.len() < default_size {
+                v.resize(default_size, 0);
+            } else {
+                v.truncate(default_size);
+            }
+            v
+        }
+        None => vec![0u8; default_size],
+    }
+}
+
+struct DecodedSection {
+    section_y: i32,
+    blocks: Vec<u8>,
+    data: Vec<u8>,
+    sky_light: Option<Vec<u8>>,
+    block_light: Option<Vec<u8>>,
+    non_air_count: u32,
+}
+
+fn count_non_air(blocks: &[u8]) -> u32 {
+    blocks.iter().filter(|&&b| b != 0).count() as u32
+}
+
+fn try_decode_section_blocks(
+    section: &nbt::NbtCompound,
+) -> Option<(Vec<u8>, Vec<u8>)> {
+    if let Some(old_blocks) = section.byte_array("Blocks") {
+        if old_blocks.len() >= 4096 {
+            let blocks = old_blocks[..4096].to_vec();
+            let data = section
+                .byte_array("Data")
+                .map(|d| d.to_vec())
+                .unwrap_or_else(|| vec![0u8; CHUNK_NIBBLES]);
+            return Some((blocks, data));
+        }
+    }
+    try_decode_palette_section(section)
+}
+
+fn try_decode_palette_section(section: &nbt::NbtCompound) -> Option<(Vec<u8>, Vec<u8>)> {
+    let mut blocks = vec![0u8; 4096];
+    let mut data = vec![0u8; 2048];
+    let block_states_container = section.compound("block_states");
+    let palette = section
+        .list("Palette")
+        .or_else(|| {
+            block_states_container
+                .and_then(|bs| bs.list("palette"))
+        });
+
+    let palette = palette?;
+    if palette.is_empty() {
+        return None;
+    }
+
+    if palette.len() == 1 {
+        if let nbt::NbtValue::Compound(entry) = &palette[0] {
+            let lb = block_mapping::map_modern_block_state(entry);
+            blocks.fill(lb.id);
+            if lb.data != 0 {
+                for i in 0..4096 {
+                    nbt::set_nibble(&mut data, i, lb.data);
+                }
+            }
+            return Some((blocks, data));
+        }
+        return None;
+    }
+
+    let block_states_tag = section
+        .long_array("BlockStates")
+        .or_else(|| {
+            block_states_container
+                .and_then(|bs| bs.long_array("data"))
+        })?;
+
+    if block_states_tag.is_empty() {
+        return None;
+    }
+
+    let bits_per_block = get_bits_required(palette.len() - 1).max(4);
+    let values_per_long = (64 / bits_per_block).max(1);
+    let expected_long_count = (4096 + values_per_long - 1) / values_per_long;
+    let use_padded = block_states_tag.len() == expected_long_count;
+    for i in 0..4096 {
+        let palette_index = if use_padded {
+            read_padded_block_state(block_states_tag, bits_per_block, i)
+        } else {
+            read_compact_block_state(block_states_tag, bits_per_block, i)
+        };
+
+        if (palette_index as usize) >= palette.len() {
+            continue;
+        }
+
+        if let nbt::NbtValue::Compound(entry) = &palette[palette_index] {
+            let legacy = block_mapping::map_modern_block_state(entry);
+            blocks[i] = legacy.id;
+            if legacy.data != 0 {
+                nbt::set_nibble(&mut data, i, legacy.data);
+            }
+        }
+    }
+
+    Some((blocks, data))
+}
+
+fn get_bits_required(value: usize) -> usize {
+    let mut bits = 0;
+    let mut v = value;
+    while v > 0 {
+        bits += 1;
+        v >>= 1;
+    }
+    bits.max(1)
+}
+
+fn read_padded_block_state(block_states: &[i64], bits_per_block: usize, index: usize) -> usize {
+    let values_per_long = (64 / bits_per_block).max(1);
+    let long_index = index / values_per_long;
+    let bit_offset = (index % values_per_long) * bits_per_block;
+    let mask = (1u64 << bits_per_block) - 1;
+    ((block_states[long_index] as u64 >> bit_offset) & mask) as usize
+}
+
+fn read_compact_block_state(block_states: &[i64], bits_per_block: usize, index: usize) -> usize {
+    let start_bit = index * bits_per_block;
+    let long_index = start_bit >> 6;
+    let bit_offset = start_bit & 63;
+    let mask = (1u64 << bits_per_block) - 1;
+    let mut value = block_states[long_index] as u64 >> bit_offset;
+    let bits_read = 64 - bit_offset;
+    if bits_read < bits_per_block && long_index + 1 < block_states.len() {
+        value |= (block_states[long_index + 1] as u64) << bits_read;
+    }
+    (value & mask) as usize
+}
+
+fn flatten_anvil_sections(
+    level: &nbt::NbtCompound,
+    format_info: &JavaChunkFormatInfo,
+    global_section_shift: &mut Option<i32>,
+) -> (Vec<u8>, Vec<u8>, Vec<u8>, Vec<u8>) {
+    let mut blocks = vec![0u8; CHUNK_BLOCKS];
+    let mut data = vec![0u8; CHUNK_NIBBLES];
+    let mut sky_light = vec![0xFFu8; CHUNK_NIBBLES];
+    let mut block_light = vec![0u8; CHUNK_NIBBLES];
+    let sections = level
+        .list("Sections")
+        .or_else(|| level.list("sections"));
+
+    let sections = match sections {
+        Some(s) => s,
+        None => return (blocks, data, sky_light, block_light),
+    };
+
+    let mut decoded_sections: Vec<DecodedSection> = Vec::new();
+    for tag in sections {
+        if let nbt::NbtValue::Compound(section) = tag {
+            let section_y = match read_section_y(section) {
+                Some(y) => y,
+                None => continue,
+            };
+
+            let (s_blocks, s_data) = match try_decode_section_blocks(section) {
+                Some(v) => v,
+                None => continue,
+            };
+
+            let s_sky = section
+                .byte_array("SkyLight")
+                .or_else(|| section.byte_array("sky_light"))
+                .map(|b| b.to_vec());
+            let s_block = section
+                .byte_array("BlockLight")
+                .or_else(|| section.byte_array("block_light"))
+                .map(|b| b.to_vec());
+
+            let non_air = count_non_air(&s_blocks);
+            decoded_sections.push(DecodedSection {
+                section_y,
+                blocks: s_blocks,
+                data: s_data,
+                sky_light: s_sky,
+                block_light: s_block,
+                non_air_count: non_air,
+            });
+        }
+    }
+
+    if decoded_sections.is_empty() {
+        return (blocks, data, sky_light, block_light);
+    }
+
+    let mut section_shift = 0;
+    if format_info.requires_section_shift() {
+        if global_section_shift.is_none() {
+            let anchor = decoded_sections
+                .iter()
+                .max_by_key(|s| (s.non_air_count, -(s.section_y - 4).abs()))
+                .map(|s| s.section_y)
+                .unwrap_or(4);
+            *global_section_shift = Some(anchor - 4);
+        }
+        section_shift = global_section_shift.unwrap_or(0);
+    }
+
+    for section in &decoded_sections {
+        let remapped_y = section.section_y - section_shift;
+        if remapped_y < 0 || remapped_y > 15 {
+            continue;
+        }
+
+        let base_y = remapped_y * 16;
+        for i in 0..4096 {
+            let x = i & 0x0F;
+            let z = (i >> 4) & 0x0F;
+            let y = (i >> 8) & 0x0F;
+            let global_y = base_y + y as i32;
+            if global_y < 0 || global_y >= 256 {
+                continue;
+            }
+            let flat_index = ((x * 16) + z) * 256 + global_y as usize;
+            if flat_index < CHUNK_BLOCKS {
+                blocks[flat_index] = section.blocks[i];
+                if section.data.len() > i {
+                    nbt::set_nibble(&mut data, flat_index, nbt::get_nibble(&section.data, i));
+                }
+                if let Some(ref sky) = section.sky_light {
+                    if sky.len() > i {
+                        nbt::set_nibble(&mut sky_light, flat_index, nbt::get_nibble(sky, i));
+                    }
+                }
+                if let Some(ref bl) = section.block_light {
+                    if bl.len() > i {
+                        nbt::set_nibble(&mut block_light, flat_index, nbt::get_nibble(bl, i));
+                    }
+                }
+            }
+        }
+    }
+
+    (blocks, data, sky_light, block_light)
+}
+
+pub fn convert_chunk(
+    root_tag: &nbt::NbtCompound,
+    new_chunk_x: i32,
+    new_chunk_z: i32,
+    preserve_dynamic: bool,
+) -> Vec<u8> {
+    let level = build_legacy_chunk_level(root_tag, new_chunk_x, new_chunk_z, preserve_dynamic);
+    payload::encode_legacy_nbt(&level)
+}
+
+pub fn convert_chunk_for_save(
+    root_tag: &nbt::NbtCompound,
+    new_chunk_x: i32,
+    new_chunk_z: i32,
+    preserve_dynamic: bool,
+) -> Vec<u8> {
+    let level = build_legacy_chunk_level(root_tag, new_chunk_x, new_chunk_z, preserve_dynamic);
+    payload::encode_compressed_storage(&level)
+}
+
+fn build_legacy_chunk_level(
+    root_tag: &nbt::NbtCompound,
+    new_chunk_x: i32,
+    new_chunk_z: i32,
+    preserve_dynamic: bool,
+) -> nbt::NbtCompound {
+    let format_info = inspect_chunk(root_tag);
+    let source_level = root_tag
+        .compound("Level")
+        .unwrap_or(root_tag);
+    let is_modern = format_info.uses_modern_content_schema();
+    let (mut blocks, mut data, mut sky_light, mut block_light) =
+        if format_info.is_section_based() {
+            flatten_anvil_sections(source_level, &format_info, &mut None)
+        } else {
+            let b = get_byte_array_or_default(source_level, "Blocks", CHUNK_BLOCKS);
+            let d = get_byte_array_or_default(source_level, "Data", CHUNK_NIBBLES);
+            let s = get_byte_array_or_default(source_level, "SkyLight", CHUNK_NIBBLES);
+            let bl = get_byte_array_or_default(source_level, "BlockLight", CHUNK_NIBBLES);
+            (b, d, s, bl)
+        };
+
+    let height_map = get_byte_array_or_default(source_level, "HeightMap", HEIGHTMAP_SIZE);
+    let mut biomes = get_byte_array_or_default(source_level, "Biomes", BIOMES_SIZE);
+    if is_modern {
+        biomes.fill(1);
+    }
+
+    block_mapping::remap_blocks(&mut blocks, &mut data);
+    let last_update = source_level.long("LastUpdate").unwrap_or(0);
+    let inhabited_time = source_level.long("InhabitedTime").unwrap_or(0);
+    const TERRAIN_POPULATED_FLAGS: i16 = 0;
+    sky_light.fill(0);
+    block_light.fill(0);
+    let mut level = nbt::NbtCompound::new("Level");
+    level.insert("xPos", nbt::NbtValue::Int(new_chunk_x));
+    level.insert("zPos", nbt::NbtValue::Int(new_chunk_z));
+    level.insert("LastUpdate", nbt::NbtValue::Long(last_update));
+    level.insert("InhabitedTime", nbt::NbtValue::Long(inhabited_time));
+    level.insert("Blocks", nbt::NbtValue::ByteArray(blocks));
+    level.insert("Data", nbt::NbtValue::ByteArray(data));
+    level.insert("SkyLight", nbt::NbtValue::ByteArray(sky_light));
+    level.insert("BlockLight", nbt::NbtValue::ByteArray(block_light));
+    level.insert("HeightMap", nbt::NbtValue::ByteArray(height_map));
+    level.insert("TerrainPopulatedFlags", nbt::NbtValue::Short(TERRAIN_POPULATED_FLAGS));
+    level.insert("Biomes", nbt::NbtValue::ByteArray(biomes));
+    let source_chunk_x = source_level.int("xPos").unwrap_or(new_chunk_x);
+    let source_chunk_z = source_level.int("zPos").unwrap_or(new_chunk_z);
+    let block_offset_x = (source_chunk_x - new_chunk_x) * 16;
+    let block_offset_z = (source_chunk_z - new_chunk_z) * 16;
+    if preserve_dynamic && !is_modern {
+        let mut entities: Vec<nbt::NbtValue> = source_level
+            .list("Entities")
+            .map(|l| l.to_vec())
+            .unwrap_or_default();
+        remap_entity_positions(&mut entities, block_offset_x, block_offset_z);
+        level.insert("Entities", nbt::NbtValue::List(entities));
+    } else {
+        level.insert("Entities", nbt::NbtValue::List(Vec::new()));
+    }
+
+    let mut tile_entities = if preserve_dynamic && !is_modern {
+        build_compatible_tile_entities(source_level, false)
+    } else {
+        build_safe_sign_tile_entities(source_level, is_modern)
+    };
+    remove_unsupported_tile_entities(&mut tile_entities);
+    remap_tile_entity_positions(&mut tile_entities, block_offset_x, block_offset_z);
+    level.insert("TileEntities", nbt::NbtValue::List(tile_entities));
+    if preserve_dynamic && !is_modern {
+        if let Some(ticks) = source_level.list("TileTicks") {
+            let remapped = remap_tile_tick_positions(ticks, block_offset_x, block_offset_z);
+            level.insert("TileTicks", nbt::NbtValue::List(remapped));
+        } else if let Some(ticks) = source_level.list("block_ticks") {
+            let remapped = remap_tile_tick_positions(ticks, block_offset_x, block_offset_z);
+            level.insert("TileTicks", nbt::NbtValue::List(remapped));
+        }
+    }
+
+    level
+}
+
+fn build_compatible_tile_entities(
+    source_level: &nbt::NbtCompound,
+    is_modern: bool,
+) -> Vec<nbt::NbtValue> {
+    if !is_modern {
+        let tiles = source_level.list("TileEntities");
+        if let Some(t) = tiles {
+            return t.to_vec();
+        }
+        let tiles2 = source_level.list("block_entities");
+        if let Some(t) = tiles2 {
+            return t.to_vec();
+        }
+        return Vec::new();
+    }
+    build_safe_sign_tile_entities(source_level, true)
+}
+
+fn build_safe_sign_tile_entities(
+    source_level: &nbt::NbtCompound,
+    is_modern: bool,
+) -> Vec<nbt::NbtValue> {
+    let mut result = Vec::new();
+    let source = if is_modern {
+        source_level
+            .list("block_entities")
+            .or_else(|| source_level.list("TileEntities"))
+    } else {
+        source_level
+            .list("TileEntities")
+            .or_else(|| source_level.list("block_entities"))
+    };
+
+    let source = match source {
+        Some(s) => s,
+        None => return result,
+    };
+
+    for tag in source {
+        if let nbt::NbtValue::Compound(block_entity) = tag {
+            let id = block_entity.string("id").unwrap_or("");
+            let is_sign = if is_modern {
+                is_modern_sign_tile_entity(id)
+            } else {
+                id == "Sign" || id == "minecraft:sign"
+            };
+            if !is_sign {
+                continue;
+            }
+            let sign = build_safe_legacy_sign_tile_entity(block_entity, is_modern);
+            result.push(nbt::NbtValue::Compound(sign));
+        }
+    }
+
+    result
+}
+
+fn is_modern_sign_tile_entity(id: &str) -> bool {
+    let stripped = id.strip_prefix("minecraft:").unwrap_or(id);
+    matches!(
+        stripped,
+        "sign"
+            | "hanging_sign"
+            | "oak_sign"
+            | "spruce_sign"
+            | "birch_sign"
+            | "jungle_sign"
+            | "acacia_sign"
+            | "dark_oak_sign"
+            | "mangrove_sign"
+            | "cherry_sign"
+            | "bamboo_sign"
+            | "crimson_sign"
+            | "warped_sign"
+            | "oak_hanging_sign"
+            | "spruce_hanging_sign"
+            | "birch_hanging_sign"
+            | "jungle_hanging_sign"
+            | "acacia_hanging_sign"
+            | "dark_oak_hanging_sign"
+            | "mangrove_hanging_sign"
+            | "cherry_hanging_sign"
+            | "bamboo_hanging_sign"
+            | "crimson_hanging_sign"
+            | "warped_hanging_sign"
+    )
+}
+
+fn read_tile_entity_coord(compound: &nbt::NbtCompound, name: &str) -> i32 {
+    compound.int(name)
+        .map(|v| v as i32)
+        .or_else(|| compound.short(name).map(|v| v as i32))
+        .or_else(|| compound.byte(name).map(|v| v as i32))
+        .unwrap_or(0)
+}
+
+fn extract_modern_sign_lines(block_entity: &nbt::NbtCompound) -> [String; 4] {
+    let mut lines: [String; 4] = Default::default();
+    if let Some(front_text) = block_entity.compound("front_text") {
+        if let Some(messages) = front_text.list("messages") {
+            for i in 0..4.min(messages.len()) {
+                if let nbt::NbtValue::String(s) = &messages[i] {
+                    lines[i] = sanitize_legacy_sign_line(&simplify_sign_text(s));
+                }
+            }
+            return lines;
+        }
+    }
+
+    for i in 0..4 {
+        let key = format!("Text{}", i + 1);
+        let value = block_entity.string(&key).unwrap_or("");
+        lines[i] = sanitize_legacy_sign_line(&simplify_sign_text(value));
+    }
+
+    lines
+}
+
+fn extract_legacy_sign_lines(block_entity: &nbt::NbtCompound) -> [String; 4] {
+    let mut lines: [String; 4] = Default::default();
+    for i in 0..4 {
+        let key = format!("Text{}", i + 1);
+        let value = block_entity.string(&key).unwrap_or("");
+        lines[i] = sanitize_legacy_sign_line(&simplify_sign_text(value));
+    }
+    lines
+}
+
+fn sanitize_legacy_sign_line(raw: &str) -> String {
+    let mut builder = String::new();
+    for ch in raw.chars() {
+        if ch == '\r' || ch == '\n' || ch == '\t' || ch == '\0' {
+            continue;
+        }
+        if ch.is_control() {
+            continue;
+        }
+        builder.push(ch);
+        if builder.len() >= 15 {
+            break;
+        }
+    }
+    builder
+}
+
+fn simplify_sign_text(raw: &str) -> String {
+    let raw = raw.trim();
+    if !(raw.starts_with('{') || raw.starts_with('[') || raw.starts_with('"')) {
+        return raw.to_string();
+    }
+
+    if let Ok(doc) = serde_json::from_str::<serde_json::Value>(raw) {
+        let mut builder = String::new();
+        append_json_text(&doc, &mut builder);
+        return builder;
+    }
+
+    raw.trim_matches('"').to_string()
+}
+
+fn append_json_text(element: &serde_json::Value, builder: &mut String) {
+    match element {
+        serde_json::Value::String(s) => builder.push_str(s),
+        serde_json::Value::Array(arr) => {
+            for item in arr {
+                append_json_text(item, builder);
+            }
+        }
+        serde_json::Value::Object(obj) => {
+            if let Some(serde_json::Value::String(text)) = obj.get("text") {
+                builder.push_str(text);
+            }
+            if let Some(extra) = obj.get("extra") {
+                append_json_text(extra, builder);
+            }
+        }
+        _ => {}
+    }
+}
+
+fn build_safe_legacy_sign_tile_entity(
+    block_entity: &nbt::NbtCompound,
+    is_modern: bool,
+) -> nbt::NbtCompound {
+    let x = read_tile_entity_coord(block_entity, "x");
+    let y = read_tile_entity_coord(block_entity, "y");
+    let z = read_tile_entity_coord(block_entity, "z");
+    let lines = if is_modern {
+        extract_modern_sign_lines(block_entity)
+    } else {
+        extract_legacy_sign_lines(block_entity)
+    };
+
+    let mut sign = nbt::NbtCompound::new("");
+    sign.insert("id", nbt::NbtValue::String("Sign".to_string()));
+    sign.insert("x", nbt::NbtValue::Int(x));
+    sign.insert("y", nbt::NbtValue::Int(y));
+    sign.insert("z", nbt::NbtValue::Int(z));
+    sign.insert("Text1", nbt::NbtValue::String(lines[0].clone()));
+    sign.insert("Text2", nbt::NbtValue::String(lines[1].clone()));
+    sign.insert("Text3", nbt::NbtValue::String(lines[2].clone()));
+    sign.insert("Text4", nbt::NbtValue::String(lines[3].clone()));
+    sign
+}
+
+fn remap_tile_tick_positions(
+    ticks: &[nbt::NbtValue],
+    block_offset_x: i32,
+    block_offset_z: i32,
+) -> Vec<nbt::NbtValue> {
+    if block_offset_x == 0 && block_offset_z == 0 {
+        return ticks.to_vec();
+    }
+    let mut result = Vec::new();
+    for tag in ticks {
+        if let nbt::NbtValue::Compound(mut tick) = tag.clone() {
+            if let Some(nbt::NbtValue::Int(x)) = tick.get_mut("x") {
+                *x -= block_offset_x;
+            }
+            if let Some(nbt::NbtValue::Int(z)) = tick.get_mut("z") {
+                *z -= block_offset_z;
+            }
+            result.push(nbt::NbtValue::Compound(tick));
+        }
+    }
+    result
+}
+
+fn remap_entity_positions(entities: &mut Vec<nbt::NbtValue>, block_offset_x: i32, block_offset_z: i32) {
+    if block_offset_x == 0 && block_offset_z == 0 {
+        return;
+    }
+    for tag in entities.iter_mut() {
+        if let nbt::NbtValue::Compound(entity) = tag {
+            if let Some(nbt::NbtValue::List(pos)) = entity.get_mut("Pos") {
+                if pos.len() >= 3 {
+                    if let nbt::NbtValue::Double(x) = &mut pos[0] {
+                        *x -= block_offset_x as f64;
+                    }
+                    if let nbt::NbtValue::Double(z) = &mut pos[2] {
+                        *z -= block_offset_z as f64;
+                    }
+                }
+            }
+            if let Some(nbt::NbtValue::Compound(riding)) = entity.get_mut("Riding") {
+                let mut inner = vec![nbt::NbtValue::Compound(riding.clone())];
+                remap_entity_positions(&mut inner, block_offset_x, block_offset_z);
+                if let Some(nbt::NbtValue::Compound(updated)) = inner.into_iter().next() {
+                    *riding = updated;
+                }
+            }
+        }
+    }
+}
+
+fn remove_unsupported_tile_entities(tile_entities: &mut Vec<nbt::NbtValue>) {
+    tile_entities.retain(|tag| {
+        if let nbt::NbtValue::Compound(te) = tag {
+            let id = te.string("id").unwrap_or("");
+            return id != "Control" && id != "minecraft:command_block" && id != "CommandBlock";
+        }
+        false
+    });
+}
+
+fn remap_tile_entity_positions(tile_entities: &mut Vec<nbt::NbtValue>, block_offset_x: i32, block_offset_z: i32) {
+    if block_offset_x == 0 && block_offset_z == 0 {
+        return;
+    }
+    for tag in tile_entities.iter_mut() {
+        if let nbt::NbtValue::Compound(te) = tag {
+            if let Some(nbt::NbtValue::Int(x)) = te.get_mut("x") {
+                *x -= block_offset_x;
+            }
+            if let Some(nbt::NbtValue::Int(z)) = te.get_mut("z") {
+                *z -= block_offset_z;
+            }
+        }
+    }
+}
+
+pub fn build_modern_anvil_level(
+    legacy_level: &nbt::NbtCompound,
+    chunk_x: i32,
+    chunk_z: i32,
+) -> nbt::NbtCompound {
+    let default_blocks = vec![0u8; 32768];
+    let default_data = vec![0u8; 16384];
+    let old_blocks_ref = legacy_level
+        .byte_array("Blocks")
+        .unwrap_or(&default_blocks);
+    let old_data_ref = legacy_level
+        .byte_array("Data")
+        .unwrap_or(&default_data);
+
+    let mut section_tags: Vec<nbt::NbtValue> = Vec::new();
+    for section_y in 0..8 {
+        let mut palette_list: Vec<String> = Vec::new();
+        let mut palette_dict: HashMap<String, usize> = HashMap::new();
+        let mut indices = [0i32; 4096];
+        let mut has_non_air = false;
+        for y in 0..16 {
+            for z in 0..16 {
+                for x in 0..16 {
+                    let global_y = section_y * 16 + y;
+                    let legacy_flat_index = ((x * 16) + z) * 128 + global_y;
+                    if legacy_flat_index >= old_blocks_ref.len() {
+                        continue;
+                    }
+                    let block_id = old_blocks_ref[legacy_flat_index];
+                    let meta = nbt::get_nibble(old_data_ref, legacy_flat_index);
+                    let modern_state = get_contextual_block_state(block_id, meta, x, global_y, z, old_blocks_ref, old_data_ref);
+                    if modern_state != "minecraft:air" {
+                        has_non_air = true;
+                    }
+
+                    let idx = *palette_dict
+                        .entry(modern_state.clone())
+                        .or_insert_with(|| {
+                            let idx = palette_list.len();
+                            palette_list.push(modern_state);
+                            idx
+                        });
+
+                    indices[y * 256 + z * 16 + x] = idx as i32;
+                }
+            }
+        }
+
+        if !has_non_air && section_y > 0 {
+            continue;
+        }
+
+        let mut section_tag = nbt::NbtCompound::new("");
+        section_tag.insert("Y", nbt::NbtValue::Byte(section_y as i8));
+        let mut block_states_tag = nbt::NbtCompound::new("block_states");
+        let mut nbt_palette: Vec<nbt::NbtValue> = Vec::new();
+        for state in &palette_list {
+            let mut p_tag = nbt::NbtCompound::new("");
+            if let Some(bracket_idx) = state.find('[') {
+                let name = &state[..bracket_idx];
+                let props_str = &state[bracket_idx + 1..state.len() - 1];
+                p_tag.insert("Name", nbt::NbtValue::String(name.to_string()));
+                let mut props_compound = nbt::NbtCompound::new("Properties");
+                for prop in props_str.split(',') {
+                    let kv: Vec<&str> = prop.splitn(2, '=').collect();
+                    if kv.len() == 2 {
+                        props_compound
+                            .insert(kv[0], nbt::NbtValue::String(kv[1].to_string()));
+                    }
+                }
+                p_tag.insert("Properties", nbt::NbtValue::Compound(props_compound));
+            } else {
+                p_tag.insert("Name", nbt::NbtValue::String(state.to_string()));
+            }
+            nbt_palette.push(nbt::NbtValue::Compound(p_tag));
+        }
+        block_states_tag.insert("palette", nbt::NbtValue::List(nbt_palette));
+        if palette_list.len() > 1 {
+            let bits_per_block = (64.0 / (palette_list.len() as f64).log2().ceil()).floor().max(4.0) as usize;
+            let values_per_long = 64 / bits_per_block;
+            let long_count = ((4096.0 / values_per_long as f64).ceil()) as usize;
+            let mut data_array = vec![0i64; long_count];
+            let mut current_long: u64 = 0;
+            let mut blocks_in_current_long = 0;
+            let mut long_index = 0;
+            for i in 0..4096 {
+                let val = indices[i] as u64;
+                current_long |= val << (blocks_in_current_long * bits_per_block);
+                blocks_in_current_long += 1;
+                if blocks_in_current_long >= values_per_long {
+                    data_array[long_index] = current_long as i64;
+                    long_index += 1;
+                    current_long = 0;
+                    blocks_in_current_long = 0;
+                }
+            }
+
+            if blocks_in_current_long > 0 {
+                data_array[long_index] = current_long as i64;
+            }
+
+            block_states_tag.insert("data", nbt::NbtValue::LongArray(data_array));
+        }
+
+        section_tag.insert("block_states", nbt::NbtValue::Compound(block_states_tag));
+        let mut biomes_tag = nbt::NbtCompound::new("biomes");
+        let biome_palette = nbt::NbtValue::List(vec![nbt::NbtValue::String(
+            "minecraft:plains".to_string(),
+        )]);
+        biomes_tag.insert("palette", biome_palette);
+        section_tag.insert("biomes", nbt::NbtValue::Compound(biomes_tag));
+        section_tags.push(nbt::NbtValue::Compound(section_tag));
+    }
+
+    let mut root = nbt::NbtCompound::new("");
+    root.insert("xPos", nbt::NbtValue::Int(chunk_x));
+    root.insert("zPos", nbt::NbtValue::Int(chunk_z));
+    root.insert("yPos", nbt::NbtValue::Int(0));
+    root.insert("Status", nbt::NbtValue::String("full".to_string()));
+    let mut block_entities: Vec<nbt::NbtValue> = Vec::new();
+    if let Some(old_te_list) = legacy_level.list("TileEntities") {
+        for old_te in old_te_list {
+            if let nbt::NbtValue::Compound(old_te_comp) = old_te {
+                let mut new_te = old_te_comp.clone();
+                let id = new_te.string("id").unwrap_or("").to_string();
+                let new_id = match id.as_str() {
+                    "Chest" => Some("minecraft:chest"),
+                    "Furnace" => Some("minecraft:furnace"),
+                    "BrewingStand" => Some("minecraft:brewing_stand"),
+                    "EnchantTable" => Some("minecraft:enchanting_table"),
+                    "Trap" => Some("minecraft:dispenser"),
+                    "MobSpawner" => Some("minecraft:mob_spawner"),
+                    "Control" => Some("minecraft:command_block"),
+                    "Beacon" => Some("minecraft:beacon"),
+                    "Skull" => Some("minecraft:skull"),
+                    "Sign" => Some("minecraft:sign"),
+                    "Cauldron" => Some("minecraft:cauldron"),
+                    "Dropper" => Some("minecraft:dropper"),
+                    "Hopper" => Some("minecraft:hopper"),
+                    "Comparator" => Some("minecraft:comparator"),
+                    "RecordPlayer" => Some("minecraft:jukebox"),
+                    "Banner" => Some("minecraft:banner"),
+                    _ if id.starts_with("minecraft:") => Some(id.as_str()),
+                    _ => None,
+                };
+
+                if let Some(nid) = new_id {
+                    new_te.insert("id", nbt::NbtValue::String(nid.to_string()));
+                    block_entities.push(nbt::NbtValue::Compound(new_te));
+                }
+            }
+        }
+    }
+
+    for i in 0..old_blocks_ref.len().min(32768) {
+        if old_blocks_ref[i] == 26 {
+            let y = i % 128;
+            let z = (i / 128) % 16;
+            let x = i / 2048;
+            let mut bed_te = nbt::NbtCompound::new("");
+            bed_te.insert("id", nbt::NbtValue::String("minecraft:bed".to_string()));
+            bed_te.insert("color", nbt::NbtValue::Int(14));
+            bed_te.insert("x", nbt::NbtValue::Int(chunk_x * 16 + x as i32));
+            bed_te.insert("y", nbt::NbtValue::Int(y as i32));
+            bed_te.insert("z", nbt::NbtValue::Int(chunk_z * 16 + z as i32));
+            block_entities.push(nbt::NbtValue::Compound(bed_te));
+        }
+    }
+
+    root.insert(
+        "block_entities",
+        nbt::NbtValue::List(block_entities),
+    );
+    root.insert("sections", nbt::NbtValue::List(section_tags));
+    root
+}
+
+fn get_contextual_block_state(
+    block_id: u8,
+    meta: u8,
+    x: usize,
+    global_y: usize,
+    z: usize,
+    old_blocks: &[u8],
+    old_data: &[u8],
+) -> String {
+    let modern_state = get_modern_block_name(block_id, meta);
+    let get_neighbor = |nx: i32, ny: i32, nz: i32| -> (u8, u8) {
+        if nx < 0 || nx > 15 || ny < 0 || ny > 127 || nz < 0 || nz > 15 {
+            return (0, 0);
+        }
+        let idx = ((nx as usize * 16) + nz as usize) * 128 + ny as usize;
+        if idx >= old_blocks.len() {
+            return (0, 0);
+        }
+        let n_id = old_blocks[idx];
+        let n_meta = nbt::get_nibble(old_data, idx);
+        (n_id, n_meta)
+    };
+
+    let bracket_index = modern_state.find('[');
+    let name = if let Some(bi) = bracket_index {
+        &modern_state[..bi]
+    } else {
+        &modern_state
+    };
+    let mut properties: HashMap<String, String> = HashMap::new();
+    if let Some(bi) = bracket_index {
+        let props_str = &modern_state[bi + 1..modern_state.len() - 1];
+        for prop in props_str.split(',') {
+            let kv: Vec<&str> = prop.splitn(2, '=').collect();
+            if kv.len() == 2 {
+                properties.insert(kv[0].to_string(), kv[1].to_string());
+            }
+        }
+    }
+
+    let mut properties_changed = false;
+    if block_id == 64 || block_id == 71 || (block_id >= 193 && block_id <= 197) {
+        let is_top = (meta & 8) == 8;
+        properties.insert("half".to_string(), if is_top { "upper" } else { "lower" }.to_string());
+        if is_top {
+            properties.insert(
+                "hinge".to_string(),
+                if (meta & 1) == 1 { "right" } else { "left" }.to_string(),
+            );
+            let (bottom_id, bottom_meta) = get_neighbor(x as i32, global_y as i32 - 1, z as i32);
+            if bottom_id == block_id {
+                let facing_meta = bottom_meta & 3;
+                properties.insert(
+                    "facing".to_string(),
+                    match facing_meta {
+                        0 => "east",
+                        1 => "south",
+                        2 => "west",
+                        _ => "north",
+                    }
+                    .to_string(),
+                );
+                properties.insert(
+                    "open".to_string(),
+                    if (bottom_meta & 4) == 4 { "true" } else { "false" }.to_string(),
+                );
+            } else {
+                properties.insert("facing".to_string(), "east".to_string());
+                properties.insert("open".to_string(), "false".to_string());
+            }
+        } else {
+            let facing_meta = meta & 3;
+            properties.insert(
+                "facing".to_string(),
+                match facing_meta {
+                    0 => "east",
+                    1 => "south",
+                    2 => "west",
+                    _ => "north",
+                }
+                .to_string(),
+            );
+            properties.insert(
+                "open".to_string(),
+                if (meta & 4) == 4 { "true" } else { "false" }.to_string(),
+            );
+            let (top_id, top_meta) = get_neighbor(x as i32, global_y as i32 + 1, z as i32);
+            properties.insert(
+                "hinge".to_string(),
+                if top_id == block_id {
+                    if (top_meta & 1) == 1 { "right" } else { "left" }
+                } else {
+                    "left"
+                }
+                .to_string(),
+            );
+        }
+        properties_changed = true;
+    } else if block_id == 63 || block_id == 68 {
+        if block_id == 68 {
+            properties.insert(
+                "facing".to_string(),
+                match meta {
+                    2 => "north",
+                    3 => "south",
+                    4 => "west",
+                    _ => "east",
+                }
+                .to_string(),
+            );
+        } else {
+            properties.insert("rotation".to_string(), meta.to_string());
+        }
+        properties.remove("waterlogged");
+        properties_changed = true;
+    } else if block_id == 50 || block_id == 75 || block_id == 76 {
+        if meta >= 1 && meta <= 4 {
+            properties.insert(
+                "facing".to_string(),
+                match meta {
+                    1 => "east",
+                    2 => "west",
+                    3 => "south",
+                    _ => "north",
+                }
+                .to_string(),
+            );
+        }
+        if block_id == 76 {
+            properties.insert("lit".to_string(), "true".to_string());
+        } else if block_id == 75 {
+            properties.insert("lit".to_string(), "false".to_string());
+        }
+        properties_changed = true;
+    } else if block_id == 54 || block_id == 146 {
+        let facing = match meta {
+            2 => "north",
+            3 => "south",
+            4 => "west",
+            5 => "east",
+            _ => "south",
+        };
+        properties.insert("type".to_string(), "single".to_string());
+        properties.insert("facing".to_string(), facing.to_string());
+        let dirs = [(-1i32, 0i32), (1, 0), (0, -1), (0, 1)];
+        for (dx, dz) in dirs {
+            let (nid, _) = get_neighbor(x as i32 + dx, global_y as i32, z as i32 + dz);
+            if nid == block_id {
+                let is_left = match facing {
+                    "north" => dx == -1,
+                    "south" => dx == 1,
+                    "west" => dz == 1,
+                    "east" => dz == -1,
+                    _ => false,
+                };
+                properties.insert(
+                    "type".to_string(),
+                    if is_left { "right" } else { "left" }.to_string(),
+                );
+                break;
+            }
+        }
+        properties_changed = true;
+    } else if is_stair_legacy(block_id) {
+        let facing = get_stair_facing(meta);
+        let half = if (meta & STAIR_UPSIDE_DOWN_BIT) != 0 {
+            "top"
+        } else {
+            "bottom"
+        };
+        properties.insert("facing".to_string(), facing.to_string());
+        properties.insert("half".to_string(), half.to_string());
+        properties.insert("shape".to_string(), "straight".to_string());
+        let (front_dx, front_dz) = match facing {
+            "north" => (0i32, 1i32),
+            "south" => (0, -1),
+            "west" => (1, 0),
+            "east" => (-1, 0),
+            _ => (0, 0),
+        };
+        let (back_dx, back_dz) = match facing {
+            "north" => (0i32, -1i32),
+            "south" => (0, 1),
+            "west" => (-1, 0),
+            "east" => (1, 0),
+            _ => (0, 0),
+        };
+
+        let back_neighbor = get_neighbor(x as i32 + back_dx, global_y as i32, z as i32 + back_dz);
+        if is_stair_legacy(back_neighbor.0) {
+            let back_facing = get_stair_facing(back_neighbor.1);
+            let back_half = if (back_neighbor.1 & STAIR_UPSIDE_DOWN_BIT) != 0 {
+                "top"
+            } else {
+                "bottom"
+            };
+            if back_half == half {
+                if let Some(side) = get_relative_side(facing, &back_facing) {
+                    properties.insert("shape".to_string(), format!("outer_{}", side));
+                }
+            }
+        } else {
+            let front_neighbor = get_neighbor(x as i32 + front_dx, global_y as i32, z as i32 + front_dz);
+            if is_stair_legacy(front_neighbor.0) {
+                let front_facing = get_stair_facing(front_neighbor.1);
+                let front_half = if (front_neighbor.1 & STAIR_UPSIDE_DOWN_BIT) != 0 {
+                    "top"
+                } else {
+                    "bottom"
+                };
+                if front_half == half {
+                    if let Some(side) = get_relative_side(facing, &front_facing) {
+                        properties.insert("shape".to_string(), format!("inner_{}", side));
+                    }
+                }
+            }
+        }
+        properties_changed = true;
+    } else if is_fence_legacy(block_id) {
+        let (n_id, _) = get_neighbor(x as i32, global_y as i32, z as i32 - 1);
+        let (e_id, _) = get_neighbor(x as i32 + 1, global_y as i32, z as i32);
+        let (s_id, _) = get_neighbor(x as i32, global_y as i32, z as i32 + 1);
+        let (w_id, _) = get_neighbor(x as i32 - 1, global_y as i32, z as i32);
+        properties.insert(
+            "north".to_string(),
+            (is_fence_legacy(n_id) || is_fence_gate_legacy(n_id) || is_likely_solid_attachment(n_id))
+                .to_string(),
+        );
+        properties.insert(
+            "east".to_string(),
+            (is_fence_legacy(e_id) || is_fence_gate_legacy(e_id) || is_likely_solid_attachment(e_id))
+                .to_string(),
+        );
+        properties.insert(
+            "south".to_string(),
+            (is_fence_legacy(s_id) || is_fence_gate_legacy(s_id) || is_likely_solid_attachment(s_id))
+                .to_string(),
+        );
+        properties.insert(
+            "west".to_string(),
+            (is_fence_legacy(w_id) || is_fence_gate_legacy(w_id) || is_likely_solid_attachment(w_id))
+                .to_string(),
+        );
+        properties_changed = true;
+    } else if is_pane_legacy(block_id) {
+        let (n_id, _) = get_neighbor(x as i32, global_y as i32, z as i32 - 1);
+        let (e_id, _) = get_neighbor(x as i32 + 1, global_y as i32, z as i32);
+        let (s_id, _) = get_neighbor(x as i32, global_y as i32, z as i32 + 1);
+        let (w_id, _) = get_neighbor(x as i32 - 1, global_y as i32, z as i32);
+        properties.insert(
+            "north".to_string(),
+            (is_pane_legacy(n_id) || is_glass_legacy(n_id) || is_likely_solid_attachment(n_id))
+                .to_string(),
+        );
+        properties.insert(
+            "east".to_string(),
+            (is_pane_legacy(e_id) || is_glass_legacy(e_id) || is_likely_solid_attachment(e_id))
+                .to_string(),
+        );
+        properties.insert(
+            "south".to_string(),
+            (is_pane_legacy(s_id) || is_glass_legacy(s_id) || is_likely_solid_attachment(s_id))
+                .to_string(),
+        );
+        properties.insert(
+            "west".to_string(),
+            (is_pane_legacy(w_id) || is_glass_legacy(w_id) || is_likely_solid_attachment(w_id))
+                .to_string(),
+        );
+        properties_changed = true;
+    }
+
+    if properties_changed || name == "minecraft:red_bed" {
+        if !properties.is_empty() {
+            let parts: Vec<String> = properties.iter().map(|(k, v)| format!("{}={}", k, v)).collect();
+            return format!("{}[{}]", name, parts.join(","));
+        }
+        return name.to_string();
+    }
+
+    modern_state
+}
+
+fn get_modern_block_name(block_id: u8, meta: u8) -> String {
+    let name = get_contextual_modern_name(block_id, meta);
+    if let Some(props) = get_contextual_properties(block_id, meta) {
+        format!("{}[{}]", name, props)
+    } else {
+        name
+    }
+}
+
+fn get_contextual_modern_name(block_id: u8, meta: u8) -> String {
+    match block_id {
+        0 => "minecraft:air".into(),
+        1 => "minecraft:stone".into(),
+        2 => "minecraft:grass_block".into(),
+        3 => "minecraft:dirt".into(),
+        4 => "minecraft:cobblestone".into(),
+        5 => match meta {
+            1 => "minecraft:spruce_planks",
+            2 => "minecraft:birch_planks",
+            3 => "minecraft:jungle_planks",
+            _ => "minecraft:oak_planks",
+        }
+        .into(),
+        6 => match meta {
+            1 => "minecraft:spruce_sapling",
+            2 => "minecraft:birch_sapling",
+            3 => "minecraft:jungle_sapling",
+            _ => "minecraft:oak_sapling",
+        }
+        .into(),
+        7 => "minecraft:bedrock".into(),
+        8 | 9 => "minecraft:water".into(),
+        10 | 11 => "minecraft:lava".into(),
+        12 => "minecraft:sand".into(),
+        13 => "minecraft:gravel".into(),
+        14 => "minecraft:gold_ore".into(),
+        15 => "minecraft:iron_ore".into(),
+        16 => "minecraft:coal_ore".into(),
+        17 => match meta & 3 {
+            1 => "minecraft:spruce_log",
+            2 => "minecraft:birch_log",
+            3 => "minecraft:jungle_log",
+            _ => "minecraft:oak_log",
+        }
+        .into(),
+        18 => match meta & 3 {
+            1 => "minecraft:spruce_leaves",
+            2 => "minecraft:birch_leaves",
+            3 => "minecraft:jungle_leaves",
+            _ => "minecraft:oak_leaves",
+        }
+        .into(),
+        19 => "minecraft:sponge".into(),
+        20 => "minecraft:glass".into(),
+        21 => "minecraft:lapis_ore".into(),
+        22 => "minecraft:lapis_block".into(),
+        23 => "minecraft:dispenser".into(),
+        24 => match meta {
+            1 => "minecraft:chiseled_sandstone",
+            2 => "minecraft:smooth_sandstone",
+            _ => "minecraft:sandstone",
+        }
+        .into(),
+        25 => "minecraft:note_block".into(),
+        26 => "minecraft:red_bed".into(),
+        27 => "minecraft:powered_rail".into(),
+        28 => "minecraft:detector_rail".into(),
+        29 => "minecraft:sticky_piston".into(),
+        30 => "minecraft:cobweb".into(),
+        31 => "minecraft:short_grass".into(),
+        32 => "minecraft:dead_bush".into(),
+        33 => "minecraft:piston".into(),
+        35 => match meta {
+            1 => "minecraft:orange_wool",
+            2 => "minecraft:magenta_wool",
+            3 => "minecraft:light_blue_wool",
+            4 => "minecraft:yellow_wool",
+            5 => "minecraft:lime_wool",
+            6 => "minecraft:pink_wool",
+            7 => "minecraft:gray_wool",
+            8 => "minecraft:light_gray_wool",
+            9 => "minecraft:cyan_wool",
+            10 => "minecraft:purple_wool",
+            11 => "minecraft:blue_wool",
+            12 => "minecraft:brown_wool",
+            13 => "minecraft:green_wool",
+            14 => "minecraft:red_wool",
+            15 => "minecraft:black_wool",
+            _ => "minecraft:white_wool",
+        }
+        .into(),
+        37 => "minecraft:dandelion".into(),
+        38 => "minecraft:poppy".into(),
+        39 => "minecraft:brown_mushroom".into(),
+        40 => "minecraft:red_mushroom".into(),
+        41 => "minecraft:gold_block".into(),
+        42 => "minecraft:iron_block".into(),
+        44 => {
+            let variant = meta & 7;
+            let name = match variant {
+                1 => "minecraft:sandstone_slab",
+                2 => "minecraft:stone_slab",
+                3 => "minecraft:cobblestone_slab",
+                4 => "minecraft:brick_slab",
+                5 => "minecraft:stone_brick_slab",
+                6 => "minecraft:nether_brick_slab",
+                7 => "minecraft:quartz_slab",
+                _ => "minecraft:stone_slab",
+            };
+            return name.to_string();
+        }
+        45 => "minecraft:bricks".into(),
+        46 => "minecraft:tnt".into(),
+        47 => "minecraft:bookshelf".into(),
+        48 => "minecraft:mossy_cobblestone".into(),
+        49 => "minecraft:obsidian".into(),
+        50 => "minecraft:torch".into(),
+        51 => "minecraft:fire".into(),
+        52 => "minecraft:mob_spawner".into(),
+        53 => "minecraft:oak_stairs".into(),
+        54 => "minecraft:chest".into(),
+        55 => "minecraft:redstone_wire".into(),
+        56 => "minecraft:diamond_ore".into(),
+        57 => "minecraft:diamond_block".into(),
+        58 => "minecraft:crafting_table".into(),
+        59 => "minecraft:wheat".into(),
+        60 => "minecraft:farmland".into(),
+        61 => "minecraft:furnace".into(),
+        63 => "minecraft:oak_sign".into(),
+        64 => "minecraft:oak_door".into(),
+        65 => "minecraft:ladder".into(),
+        66 => "minecraft:rail".into(),
+        67 => "minecraft:cobblestone_stairs".into(),
+        68 => "minecraft:oak_wall_sign".into(),
+        69 => "minecraft:lever".into(),
+        70 => "minecraft:stone_pressure_plate".into(),
+        71 => "minecraft:iron_door".into(),
+        72 => "minecraft:oak_pressure_plate".into(),
+        73 => "minecraft:redstone_ore".into(),
+        75 => "minecraft:redstone_wall_torch".into(),
+        76 => "minecraft:redstone_torch".into(),
+        77 => "minecraft:stone_button".into(),
+        78 => "minecraft:snow".into(),
+        79 => "minecraft:ice".into(),
+        80 => "minecraft:snow_block".into(),
+        81 => "minecraft:cactus".into(),
+        82 => "minecraft:clay".into(),
+        83 => "minecraft:sugar_cane".into(),
+        84 => "minecraft:jukebox".into(),
+        85 => "minecraft:oak_fence".into(),
+        86 => "minecraft:carved_pumpkin".into(),
+        87 => "minecraft:netherrack".into(),
+        88 => "minecraft:soul_sand".into(),
+        89 => "minecraft:glowstone".into(),
+        90 => "minecraft:nether_portal".into(),
+        91 => "minecraft:jack_o_lantern".into(),
+        92 => "minecraft:cake".into(),
+        93 => "minecraft:unpowered_repeater".into(),
+        94 => "minecraft:powered_repeater".into(),
+        96 => "minecraft:trapdoor".into(),
+        98 => "minecraft:stone_bricks".into(),
+        101 => "minecraft:iron_bars".into(),
+        102 => "minecraft:glass_pane".into(),
+        103 => "minecraft:melon".into(),
+        104 => "minecraft:pumpkin_stem".into(),
+        105 => "minecraft:melon_stem".into(),
+        106 => "minecraft:vine".into(),
+        107 => "minecraft:oak_fence_gate".into(),
+        108 => "minecraft:brick_stairs".into(),
+        109 => "minecraft:stone_brick_stairs".into(),
+        110 => "minecraft:mycelium".into(),
+        111 => "minecraft:lily_pad".into(),
+        112 => "minecraft:nether_bricks".into(),
+        113 => "minecraft:nether_brick_fence".into(),
+        114 => "minecraft:nether_brick_stairs".into(),
+        115 => "minecraft:nether_wart".into(),
+        116 => "minecraft:enchanting_table".into(),
+        117 => "minecraft:brewing_stand".into(),
+        118 => "minecraft:cauldron".into(),
+        121 => "minecraft:end_stone".into(),
+        122 => "minecraft:dragon_egg".into(),
+        123 => "minecraft:redstone_lamp".into(),
+        124 => "minecraft:redstone_lamp".into(),
+        125 => "minecraft:double_wooden_slab".into(),
+        126 => "minecraft:wooden_slab".into(),
+        127 => "minecraft:cocoa".into(),
+        128 => "minecraft:sandstone_stairs".into(),
+        129 => "minecraft:emerald_ore".into(),
+        130 => "minecraft:ender_chest".into(),
+        131 => "minecraft:tripwire_hook".into(),
+        132 => "minecraft:tripwire".into(),
+        133 => "minecraft:emerald_block".into(),
+        134 => "minecraft:spruce_stairs".into(),
+        135 => "minecraft:birch_stairs".into(),
+        136 => "minecraft:jungle_stairs".into(),
+        138 => "minecraft:beacon".into(),
+        139 => "minecraft:cobblestone_wall".into(),
+        140 => "minecraft:flower_pot".into(),
+        141 => "minecraft:carrots".into(),
+        142 => "minecraft:potatoes".into(),
+        143 => "minecraft:wooden_button".into(),
+        144 => "minecraft:skull".into(),
+        145 => "minecraft:anvil".into(),
+        146 => "minecraft:trapped_chest".into(),
+        147 => "minecraft:light_weighted_pressure_plate".into(),
+        148 => "minecraft:heavy_weighted_pressure_plate".into(),
+        149 => "minecraft:unpowered_comparator".into(),
+        150 => "minecraft:powered_comparator".into(),
+        151 => "minecraft:daylight_detector".into(),
+        152 => "minecraft:redstone_block".into(),
+        153 => "minecraft:nether_quartz_ore".into(),
+        154 => "minecraft:hopper".into(),
+        155 => match meta {
+            1 => "minecraft:chiseled_quartz_block",
+            2 => "minecraft:quartz_pillar",
+            3 => "minecraft:quartz_pillar",
+            _ => "minecraft:quartz_block",
+        }
+        .into(),
+        156 => "minecraft:quartz_stairs".into(),
+        157 => "minecraft:activator_rail".into(),
+        158 => "minecraft:dropper".into(),
+        159 => match meta {
+            0 => "minecraft:white_stained_hardened_clay",
+            1 => "minecraft:orange_stained_hardened_clay",
+            2 => "minecraft:magenta_stained_hardened_clay",
+            3 => "minecraft:light_blue_stained_hardened_clay",
+            4 => "minecraft:yellow_stained_hardened_clay",
+            5 => "minecraft:lime_stained_hardened_clay",
+            6 => "minecraft:pink_stained_hardened_clay",
+            7 => "minecraft:gray_stained_hardened_clay",
+            8 => "minecraft:light_gray_stained_hardened_clay",
+            9 => "minecraft:cyan_stained_hardened_clay",
+            10 => "minecraft:purple_stained_hardened_clay",
+            11 => "minecraft:blue_stained_hardened_clay",
+            12 => "minecraft:brown_stained_hardened_clay",
+            13 => "minecraft:green_stained_hardened_clay",
+            14 => "minecraft:red_stained_hardened_clay",
+            15 => "minecraft:black_stained_hardened_clay",
+            _ => "minecraft:white_stained_hardened_clay",
+        }
+        .into(),
+        160 => match meta {
+            0 => "minecraft:white_stained_glass_pane",
+            1 => "minecraft:orange_stained_glass_pane",
+            2 => "minecraft:magenta_stained_glass_pane",
+            3 => "minecraft:light_blue_stained_glass_pane",
+            4 => "minecraft:yellow_stained_glass_pane",
+            5 => "minecraft:lime_stained_glass_pane",
+            6 => "minecraft:pink_stained_glass_pane",
+            7 => "minecraft:gray_stained_glass_pane",
+            8 => "minecraft:light_gray_stained_glass_pane",
+            9 => "minecraft:cyan_stained_glass_pane",
+            10 => "minecraft:purple_stained_glass_pane",
+            11 => "minecraft:blue_stained_glass_pane",
+            12 => "minecraft:brown_stained_glass_pane",
+            13 => "minecraft:green_stained_glass_pane",
+            14 => "minecraft:red_stained_glass_pane",
+            15 => "minecraft:black_stained_glass_pane",
+            _ => "minecraft:white_stained_glass_pane",
+        }
+        .into(),
+        161 => match meta & 3 {
+            1 => "minecraft:acacia_leaves",
+            _ => "minecraft:dark_oak_leaves",
+        }
+        .into(),
+        162 => match meta & 3 {
+            1 => "minecraft:acacia_log",
+            _ => "minecraft:dark_oak_log",
+        }
+        .into(),
+        163 => "minecraft:acacia_stairs".into(),
+        164 => "minecraft:dark_oak_stairs".into(),
+        170 => "minecraft:hay_block".into(),
+        171 => match meta {
+            0 => "minecraft:white_carpet",
+            1 => "minecraft:orange_carpet",
+            2 => "minecraft:magenta_carpet",
+            3 => "minecraft:light_blue_carpet",
+            4 => "minecraft:yellow_carpet",
+            5 => "minecraft:lime_carpet",
+            6 => "minecraft:pink_carpet",
+            7 => "minecraft:gray_carpet",
+            8 => "minecraft:light_gray_carpet",
+            9 => "minecraft:cyan_carpet",
+            10 => "minecraft:purple_carpet",
+            11 => "minecraft:blue_carpet",
+            12 => "minecraft:brown_carpet",
+            13 => "minecraft:green_carpet",
+            14 => "minecraft:red_carpet",
+            15 => "minecraft:black_carpet",
+            _ => "minecraft:white_carpet",
+        }
+        .into(),
+        172 => match meta {
+            0 => "minecraft:white_concrete",
+            1 => "minecraft:orange_concrete",
+            2 => "minecraft:magenta_concrete",
+            3 => "minecraft:light_blue_concrete",
+            4 => "minecraft:yellow_concrete",
+            5 => "minecraft:lime_concrete",
+            6 => "minecraft:pink_concrete",
+            7 => "minecraft:gray_concrete",
+            8 => "minecraft:light_gray_concrete",
+            9 => "minecraft:cyan_concrete",
+            10 => "minecraft:purple_concrete",
+            11 => "minecraft:blue_concrete",
+            12 => "minecraft:brown_concrete",
+            13 => "minecraft:green_concrete",
+            14 => "minecraft:red_concrete",
+            15 => "minecraft:black_concrete",
+            _ => "minecraft:white_concrete",
+        }
+        .into(),
+        173 => "minecraft:coal_block".into(),
+        95 => match meta {
+            0 => "minecraft:white_stained_glass",
+            1 => "minecraft:orange_stained_glass",
+            2 => "minecraft:magenta_stained_glass",
+            3 => "minecraft:light_blue_stained_glass",
+            4 => "minecraft:yellow_stained_glass",
+            5 => "minecraft:lime_stained_glass",
+            6 => "minecraft:pink_stained_glass",
+            7 => "minecraft:gray_stained_glass",
+            8 => "minecraft:light_gray_stained_glass",
+            9 => "minecraft:cyan_stained_glass",
+            10 => "minecraft:purple_stained_glass",
+            11 => "minecraft:blue_stained_glass",
+            12 => "minecraft:brown_stained_glass",
+            13 => "minecraft:green_stained_glass",
+            14 => "minecraft:red_stained_glass",
+            15 => "minecraft:black_stained_glass",
+            _ => "minecraft:white_stained_glass",
+        }
+        .into(),
+        _ => "minecraft:air".into(),
+    }
+}
+
+fn get_contextual_properties(block_id: u8, meta: u8) -> Option<String> {
+    match block_id {
+        63 => Some(format!("rotation={}", meta & 0x0F)),
+        68 => Some(format!(
+            "facing={}",
+            match meta {
+                2 => "north",
+                3 => "south",
+                4 => "west",
+                _ => "east",
+            }
+        )),
+        50 | 75 | 76 => {
+            if meta >= 1 && meta <= 4 {
+                Some(format!(
+                    "facing={}",
+                    match meta {
+                        1 => "east",
+                        2 => "west",
+                        3 => "south",
+                        _ => "north",
+                    }
+                ))
+            } else {
+                None
+            }
+        }
+        _ => None,
+    }
+}
+
+fn is_stair_legacy(id: u8) -> bool {
+    matches!(
+        id,
+        53 | 67 | 108 | 109 | 114 | 128 | 134 | 135 | 136 | 156 | 163 | 164 | 180
+    )
+}
+
+fn get_stair_facing(meta: u8) -> &'static str {
+    match meta & 0x3 {
+        0 => "east",
+        1 => "west",
+        2 => "south",
+        3 => "north",
+        _ => "north",
+    }
+}
+
+fn get_relative_side(current_facing: &str, neighbor_facing: &str) -> Option<&'static str> {
+    match current_facing {
+        "north" => {
+            if neighbor_facing == "west" {
+                return Some("left");
+            }
+            if neighbor_facing == "east" {
+                return Some("right");
+            }
+        }
+        "south" => {
+            if neighbor_facing == "east" {
+                return Some("left");
+            }
+            if neighbor_facing == "west" {
+                return Some("right");
+            }
+        }
+        "west" => {
+            if neighbor_facing == "south" {
+                return Some("left");
+            }
+            if neighbor_facing == "north" {
+                return Some("right");
+            }
+        }
+        "east" => {
+            if neighbor_facing == "north" {
+                return Some("left");
+            }
+            if neighbor_facing == "south" {
+                return Some("right");
+            }
+        }
+        _ => {}
+    }
+    None
+}
+
+fn is_fence_legacy(id: u8) -> bool {
+    matches!(id, 85 | 113 | 188 | 189 | 190 | 191 | 192)
+}
+
+fn is_fence_gate_legacy(id: u8) -> bool {
+    matches!(id, 107 | 183 | 184 | 185 | 186 | 187)
+}
+
+fn is_pane_legacy(id: u8) -> bool {
+    matches!(id, 101 | 102 | 160)
+}
+
+fn is_glass_legacy(id: u8) -> bool {
+    matches!(id, 20 | 95)
+}
+
+fn is_likely_solid_attachment(id: u8) -> bool {
+    if id == 0 {
+        return false;
+    }
+    if id >= 8 && id <= 11 {
+        return false;
+    }
+    !matches!(
+        id,
+        6 | 27 | 28 | 30 | 31 | 32 | 37 | 38 | 39 | 40 | 50 | 51 | 55 | 59 | 63 | 65 | 66
+            | 68 | 69 | 70 | 71 | 72 | 75 | 76 | 77 | 78 | 83 | 90 | 92 | 93 | 94 | 96 | 101
+            | 102 | 104 | 105 | 106 | 107 | 111 | 115 | 119 | 127 | 131 | 132 | 141 | 142 | 143
+            | 147 | 148 | 149 | 150 | 157 | 160 | 171 | 175
+    )
+}
diff --git a/src-tauri/src/commands/java2lce/level_dat.rs b/src-tauri/src/commands/java2lce/level_dat.rs
new file mode 100644
index 0000000..dba4f04
--- /dev/null
+++ b/src-tauri/src/commands/java2lce/level_dat.rs
@@ -0,0 +1,251 @@
+use super::nbt::{self, NbtCompound, NbtValue};
+pub struct SpawnPoint {
+    pub x: i32,
+    pub y: i32,
+    pub z: i32,
+}
+
+pub fn read_spawn(root: &NbtCompound) -> SpawnPoint {
+    let data = match root.compound("Data") {
+        Some(d) => d,
+        None => {
+            return SpawnPoint { x: 0, y: 64, z: 0 };
+        }
+    };
+
+    if let (Some(sx), Some(sz)) = (data.int("SpawnX"), data.int("SpawnZ")) {
+        return SpawnPoint {
+            x: sx,
+            y: data.int("SpawnY").unwrap_or(64),
+            z: sz,
+        };
+    }
+
+    if let Some(spawn_comp) = data.compound("spawn") {
+        if let Some(pos) = spawn_comp.int_array("pos") {
+            if pos.len() >= 3 {
+                return SpawnPoint {
+                    x: pos[0],
+                    y: pos[1],
+                    z: pos[2],
+                };
+            }
+        }
+    }
+
+    SpawnPoint { x: 0, y: 64, z: 0 }
+}
+
+pub fn convert_java_to_lce(
+    java_root: &NbtCompound,
+    spawn_chunk_x: i32,
+    spawn_chunk_z: i32,
+    xz_size: i32,
+    flat_world: bool,
+    override_spawn_y: Option<i32>,
+) -> Vec<u8> {
+    let java_data = java_root
+        .compound("Data")
+        .expect("Java level.dat missing 'Data' compound tag");
+
+    let data_version = java_data
+        .int("DataVersion")
+        .or_else(|| java_root.int("DataVersion"))
+        .unwrap_or(0);
+    let is_modern_world = data_version >= 1519;
+    let hell_scale: i32 = 3;
+    let spawn = read_spawn(java_root);
+    let spawn_x = spawn.x;
+    let spawn_y = if let Some(oy) = override_spawn_y {
+        oy.clamp(1, 127)
+    } else if is_modern_world {
+        64
+    } else {
+        spawn.y.clamp(1, 127)
+    };
+    let spawn_z = spawn.z;
+    let new_spawn_x = spawn_x - (spawn_chunk_x * 16);
+    let new_spawn_z = spawn_z - (spawn_chunk_z * 16);
+    let safe_generator_name = if flat_world {
+        "flat".to_string()
+    } else if is_modern_world {
+        "default".to_string()
+    } else {
+        get_string(java_data, "generatorName", "default")
+    };
+    let safe_generator_version = if flat_world {
+        0
+    } else if is_modern_world {
+        1
+    } else {
+        get_int(java_data, "generatorVersion")
+    };
+    let safe_generator_options = if flat_world {
+        get_string(java_data, "generatorOptions", "2;7,2x3,2;1;")
+    } else if is_modern_world {
+        "".to_string()
+    } else {
+        get_string(java_data, "generatorOptions", "")
+    };
+
+    let mut lce_data = NbtCompound::new("Data");
+    lce_data.insert("RandomSeed", NbtValue::Long(get_long(java_data, "RandomSeed")));
+    lce_data.insert("generatorName", NbtValue::String(safe_generator_name));
+    lce_data.insert("generatorVersion", NbtValue::Int(safe_generator_version));
+    lce_data.insert("generatorOptions", NbtValue::String(safe_generator_options));
+    lce_data.insert("GameType", NbtValue::Int(get_int(java_data, "GameType")));
+    lce_data.insert("MapFeatures", NbtValue::Byte(get_bool(java_data, "MapFeatures", true)));
+    lce_data.insert("SpawnX", NbtValue::Int(new_spawn_x));
+    lce_data.insert("SpawnY", NbtValue::Int(spawn_y));
+    lce_data.insert("SpawnZ", NbtValue::Int(new_spawn_z));
+    lce_data.insert("Time", NbtValue::Long(get_long(java_data, "Time")));
+    lce_data.insert("DayTime", NbtValue::Long(get_long(java_data, "DayTime")));
+    lce_data.insert("SizeOnDisk", NbtValue::Long(0));
+    lce_data.insert("LastPlayed", NbtValue::Long(unix_timestamp_millis()));
+    lce_data.insert(
+        "LevelName",
+        NbtValue::String(get_string(java_data, "LevelName", "Converted World")),
+    );
+    lce_data.insert("version", NbtValue::Int(19133));
+    lce_data.insert("rainTime", NbtValue::Int(get_int(java_data, "rainTime")));
+    lce_data.insert("raining", NbtValue::Byte(get_bool(java_data, "raining", false)));
+    lce_data.insert("thunderTime", NbtValue::Int(get_int(java_data, "thunderTime")));
+    lce_data.insert(
+        "thundering",
+        NbtValue::Byte(get_bool(java_data, "thundering", false)),
+    );
+    lce_data.insert(
+        "hardcore",
+        NbtValue::Byte(get_bool(java_data, "hardcore", false)),
+    );
+    lce_data.insert(
+        "allowCommands",
+        NbtValue::Byte(get_bool(java_data, "allowCommands", false)),
+    );
+    lce_data.insert(
+        "initialized",
+        NbtValue::Byte(get_bool(java_data, "initialized", true)),
+    );
+
+    lce_data.insert("newSeaLevel", NbtValue::Byte(1));
+    lce_data.insert(
+        "hasBeenInCreative",
+        NbtValue::Byte(get_bool(java_data, "hasBeenInCreative", false)),
+    );
+    lce_data.insert(
+        "spawnBonusChest",
+        NbtValue::Byte(get_bool(java_data, "spawnBonusChest", false)),
+    );
+
+    lce_data.insert("hasStronghold", NbtValue::Byte(0));
+    lce_data.insert("StrongholdX", NbtValue::Int(0));
+    lce_data.insert("StrongholdY", NbtValue::Int(0));
+    lce_data.insert("StrongholdZ", NbtValue::Int(0));
+    lce_data.insert("hasStrongholdEndPortal", NbtValue::Byte(0));
+    lce_data.insert("StrongholdEndPortalX", NbtValue::Int(0));
+    lce_data.insert("StrongholdEndPortalZ", NbtValue::Int(0));
+    lce_data.insert("XZSize", NbtValue::Int(xz_size));
+    lce_data.insert("HellScale", NbtValue::Int(hell_scale));
+    if !is_modern_world {
+        if let Some(game_rules) = java_data.get("GameRules") {
+            lce_data.insert("GameRules", game_rules.clone());
+        }
+    }
+
+    let mut root = NbtCompound::new("");
+    root.insert("Data", NbtValue::Compound(lce_data));
+    nbt::write_nbt(&root)
+}
+
+pub fn convert_lce_to_java(
+    lce_root: &NbtCompound,
+    override_spawn_x: Option<i32>,
+    override_spawn_y: Option<i32>,
+    override_spawn_z: Option<i32>,
+    embedded_player: Option<&NbtCompound>,
+) -> Vec<u8> {
+    let lce_data = lce_root.compound("Data").unwrap_or(lce_root);
+    let mut java_data = lce_data.clone();
+    let lce_only_fields = [
+        "newSeaLevel",
+        "hasBeenInCreative",
+        "spawnBonusChest",
+        "XZSize",
+        "xzSize",
+        "HellScale",
+        "hellScale",
+        "hasStronghold",
+        "StrongholdX",
+        "StrongholdY",
+        "StrongholdZ",
+        "hasStrongholdEndPortal",
+        "StrongholdEndPortalX",
+        "StrongholdEndPortalZ",
+        "xStronghold",
+        "yStronghold",
+        "zStronghold",
+        "hasStrongholdEP",
+        "xStrongholdEP",
+        "zStrongholdEP",
+    ];
+
+    for field in lce_only_fields {
+        java_data.remove(field);
+    }
+
+    if let Some(sx) = override_spawn_x {
+        java_data.insert("SpawnX", NbtValue::Int(sx));
+    }
+    if let Some(sy) = override_spawn_y {
+        java_data.insert("SpawnY", NbtValue::Int(sy));
+    }
+    if let Some(sz) = override_spawn_z {
+        java_data.insert("SpawnZ", NbtValue::Int(sz));
+    }
+
+    java_data.insert("version", NbtValue::Int(19133));
+    java_data.insert("DataVersion", NbtValue::Int(1343));
+    let mut version_compound = NbtCompound::new("Version");
+    version_compound.insert("Id", NbtValue::Int(1343));
+    version_compound.insert("Name", NbtValue::String("1.12.2".to_string()));
+    version_compound.insert("Snapshot", NbtValue::Byte(0));
+    java_data.insert("Version", NbtValue::Compound(version_compound));
+    if let Some(player) = embedded_player {
+        let mut player_tag = player.clone();
+        player_tag.name = "Player".to_string();
+        java_data.insert("Player", NbtValue::Compound(player_tag));
+    }
+
+    java_data.insert("LastPlayed", NbtValue::Long(unix_timestamp_millis()));
+    let mut java_root = NbtCompound::new("");
+    let mut data_tag = NbtCompound::new("Data");
+    for (name, value) in &java_data.tags {
+        data_tag.insert(name, value.clone());
+    }
+    java_root.insert("Data", NbtValue::Compound(data_tag));
+
+    nbt::write_gzip_nbt(&java_root)
+}
+
+fn get_long(compound: &NbtCompound, name: &str) -> i64 {
+    compound.long(name).unwrap_or(0)
+}
+
+fn get_int(compound: &NbtCompound, name: &str) -> i32 {
+    compound.int(name).unwrap_or(0)
+}
+
+fn get_string(compound: &NbtCompound, name: &str, default: &str) -> String {
+    compound.string(name).unwrap_or(default).to_string()
+}
+
+fn get_bool(compound: &NbtCompound, name: &str, default: bool) -> i8 {
+    compound.byte(name).unwrap_or(if default { 1 } else { 0 })
+}
+
+fn unix_timestamp_millis() -> i64 {
+    std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_millis() as i64
+}
diff --git a/src-tauri/src/commands/java2lce/mod.rs b/src-tauri/src/commands/java2lce/mod.rs
new file mode 100644
index 0000000..3531912
--- /dev/null
+++ b/src-tauri/src/commands/java2lce/mod.rs
@@ -0,0 +1,235 @@
+pub mod block_mapping;
+pub mod chunk;
+pub mod payload;
+pub mod level_dat;
+pub mod nbt;
+pub mod region;
+use std::fs;
+use std::path::Path;
+use tauri::AppHandle;
+use std::collections::HashMap;
+use region::{JavaWorldReader, JavaRegionFileWriter, LceRegionFile, SaveDataContainer};
+use chunk::{convert_chunk_for_save, build_modern_anvil_level};
+use level_dat::{read_spawn, convert_java_to_lce, convert_lce_to_java};
+const REGION_SECT_COUNT: usize = 1024;
+#[tauri::command]
+#[allow(non_snake_case)]
+pub async fn java_to_lce(
+    _app: AppHandle,
+    java_world_path: String,
+    output_ms_path: String,
+) -> Result<String, String> {
+    let reader = JavaWorldReader::new(&java_world_path);
+    let java_root = reader.read_level_dat().map_err(|e| format!("Failed to read level.dat: {}", e))?;
+    let spawn = read_spawn(&java_root);
+    let spawn_chunk_x = spawn.x >> 4;
+    let spawn_chunk_z = spawn.z >> 4;
+    let region_files = reader.get_region_files("");
+    let total_regions = region_files.len();
+    let mut container = SaveDataContainer::new(0, 0);
+    let level_dat_bytes = convert_java_to_lce(
+        &java_root,
+        spawn_chunk_x,
+        spawn_chunk_z,
+        864,
+        false,
+        None,
+    );
+    let ld_idx = container.create_file("level.dat");
+    container.write_to_file(ld_idx, &level_dat_bytes);
+    let mut java_reader = JavaWorldReader::new(&java_world_path);
+    let mut chunks_written: usize = 0;
+    let mut errors: Vec<String> = Vec::new();
+    for (ri, &(_, _, ref region_path)) in region_files.iter().enumerate() {
+        let parts: Vec<&str> = region_path.split('.').collect();
+        let region_x: i32 = if parts.len() >= 2 {
+            parts[parts.len() - 3].parse().unwrap_or(0)
+        } else {
+            0
+        };
+        let region_z: i32 = if parts.len() >= 2 {
+            parts[parts.len() - 2].parse().unwrap_or(0)
+        } else {
+            0
+        };
+
+        let region_filename = format!("r.{}.{}.mcr", region_x, region_z);
+        let mut lce_region = LceRegionFile::new(&region_filename);
+        let mut chunk_count = 0;
+        for local_z in 0..32 {
+            for local_x in 0..32 {
+                if !java_reader.has_chunk(region_path, local_x, local_z) {
+                    continue;
+                }
+
+                match java_reader.read_chunk_nbt(region_path, local_x, local_z) {
+                    Ok(Some(root)) => {
+                        let chunk_x = region_x * 32 + local_x;
+                        let chunk_z = region_z * 32 + local_z;
+                        let payload = convert_chunk_for_save(&root, chunk_x, chunk_z, false);
+                        lce_region.write_chunk(local_x, local_z, payload);
+                        chunk_count += 1;
+                    }
+                    Ok(None) => {}
+                    Err(e) => {
+                        errors.push(format!("r.{}/{}: {}", local_x, local_z, e));
+                    }
+                }
+            }
+        }
+
+        if chunk_count > 0 {
+            lce_region.write_to_container(&mut container);
+            chunks_written += chunk_count;
+        }
+
+        if ri % 10 == 0 {
+            eprintln!("java2lce: processed region {}/{}", ri + 1, total_regions);
+        }
+    }
+
+    container.save(&output_ms_path).map_err(|e| format!("Failed to save output: {}", e))?;
+    let mut msg = format!(
+        "Conversion complete!\nChunks: {}\nRegions: {}",
+        chunks_written, total_regions
+    );
+    if !errors.is_empty() {
+        msg.push_str(&format!("\nErrors: {}", errors.len()));
+        for err in errors.iter().take(5) {
+            msg.push_str(&format!("\n  {}", err));
+        }
+        if errors.len() > 5 {
+            msg.push_str(&format!("\n  ... and {} more", errors.len() - 5));
+        }
+    }
+    eprintln!("{}",msg);
+    Ok(msg)
+}
+
+#[tauri::command]
+#[allow(non_snake_case)]
+pub async fn lce_to_java(
+    _app: AppHandle,
+    input_ms_path: String,
+    java_world_output: String,
+) -> Result<String, String> {
+    let ms_data = fs::read(&input_ms_path).map_err(|e| format!("Failed to read saveData.ms: {}", e))?;
+    let decompressed = region::decompress_zlib(&ms_data[8..]).map_err(|e| format!("Failed to decompress save data: {}", e))?;
+    let footer_offset = u32::from_le_bytes([
+        decompressed[0], decompressed[1], decompressed[2], decompressed[3],
+    ]) as usize;
+    let entry_count = u32::from_le_bytes([
+        decompressed[4], decompressed[5], decompressed[6], decompressed[7],
+    ]) as usize;
+    let mut files: Vec<(String, Vec<u8>)> = Vec::new();
+    for i in 0..entry_count {
+        let base = footer_offset + i * 144;
+        if base + 144 > decompressed.len() {
+            break;
+        }
+
+        let name_bytes = &decompressed[base..base + 128];
+        let name: String = name_bytes
+            .chunks_exact(2)
+            .map(|c| u16::from_le_bytes([c[0], c[1]]))
+            .take_while(|&c| c != 0)
+            .filter_map(|c| char::from_u32(c as u32))
+            .collect();
+
+        let length = u32::from_le_bytes([
+            decompressed[base + 128],
+            decompressed[base + 129],
+            decompressed[base + 130],
+            decompressed[base + 131],
+        ]) as usize;
+        let start_offset = u32::from_le_bytes([
+            decompressed[base + 132],
+            decompressed[base + 133],
+            decompressed[base + 134],
+            decompressed[base + 135],
+        ]) as usize;
+        if !name.is_empty() && length > 0 && start_offset + length <= decompressed.len() {
+            let data = decompressed[start_offset..start_offset + length].to_vec();
+            files.push((name, data));
+        }
+    }
+
+    let out_dir = Path::new(&java_world_output);
+    fs::create_dir_all(out_dir).map_err(|e| format!("Failed to create output directory: {}", e))?;
+    fs::create_dir_all(out_dir.join("region")).map_err(|e| format!("Failed to create region directory: {}", e))?;
+    let mut chunks_written: usize = 0;
+    let mut errors: Vec<String> = Vec::new();
+    let mut region_writers: HashMap<String, JavaRegionFileWriter> = HashMap::new();
+    for (name, data) in &files {
+        if name == "level.dat" {
+            let lce_root = nbt::read_nbt(data).map_err(|e| format!("Failed to parse level.dat: {}", e))?;
+            let java_level_bytes = convert_lce_to_java(&lce_root, None, None, None, None);
+            fs::write(out_dir.join("level.dat"), &java_level_bytes).map_err(|e| format!("Failed to write level.dat: {}", e))?;
+            continue;
+        }
+
+        if name.ends_with(".mcr") || name.ends_with(".mca") {
+            let mut reader = region::JavaRegionReader::open_from_bytes(data);
+            let parts: Vec<&str> = name.split('.').collect();
+            let region_x: i32 = if parts.len() >= 4 { parts[1].parse().unwrap_or(0) } else { 0 };
+            let region_z: i32 = if parts.len() >= 4 { parts[2].parse().unwrap_or(0) } else { 0 };
+            for local_z in 0..32 {
+                for local_x in 0..32 {
+                    let index = (local_x & 31) + (local_z & 31) * 32;
+                    if reader.offsets[index as usize] == 0 {
+                        continue;
+                    }
+
+                    match reader.read_chunk(local_x, local_z) {
+                        Ok(Some(lce_chunk_data)) => {
+                            if let Some(legacy_nbt) = payload::try_decode_to_legacy_nbt(&lce_chunk_data) {
+                                let root = nbt::read_nbt(&legacy_nbt).unwrap_or_default();
+                                let source_level = root.compound("Level").unwrap_or(&root);
+                                let cx = region_x * 32 + local_x;
+                                let cz = region_z * 32 + local_z;
+                                let modern_root = build_modern_anvil_level(source_level, cx, cz);
+                                let modern_nbt = nbt::write_nbt(&modern_root);
+                                let out_region_x = cx >> 5;
+                                let out_region_z = cz >> 5;
+                                let out_local_x = cx & 31;
+                                let out_local_z = cz & 31;
+                                let section_region = format!("r.{}.{}.mca", out_region_x, out_region_z);
+                                let region_path = out_dir.join("region").join(&section_region);
+                                let region_path_str = region_path.to_string_lossy().to_string();
+                                let writer = region_writers.entry(section_region.clone()).or_insert_with(|| {
+                                    JavaRegionFileWriter::load_from_file(&region_path_str)
+                                });
+                                writer.write_chunk(out_local_x, out_local_z, &modern_nbt);
+                                chunks_written += 1;
+                            }
+                        }
+                        Ok(None) => {}
+                        Err(e) => {
+                            errors.push(format!("{}/{}: {}", name, local_x * 32 + local_z, e));
+                        }
+                    }
+                }
+            }
+            continue;
+        }
+    }
+
+    for (region_name, writer) in &mut region_writers {
+        if let Err(e) = writer.save() {
+            errors.push(format!("Failed to save region {}: {}", region_name, e));
+        }
+    }
+
+    let mut msg = format!(
+        "Conversion complete!\nChunks: {}\nFiles: {}",
+        chunks_written, files.len()
+    );
+    if !errors.is_empty() {
+        msg.push_str(&format!("\nErrors: {}", errors.len()));
+        for err in errors.iter().take(5) {
+            msg.push_str(&format!("\n  {}", err));
+        }
+    }
+    eprintln!("{}", msg);
+    Ok(msg)
+}
diff --git a/src-tauri/src/commands/java2lce/nbt.rs b/src-tauri/src/commands/java2lce/nbt.rs
new file mode 100644
index 0000000..bc0324f
--- /dev/null
+++ b/src-tauri/src/commands/java2lce/nbt.rs
@@ -0,0 +1,496 @@
+use std::io::{Read, Write};
+use flate2::read::GzDecoder;
+use flate2::write::GzEncoder;
+use flate2::Compression;
+#[derive(Debug, Clone, PartialEq)]
+pub enum NbtValue {
+    Byte(i8),
+    Short(i16),
+    Int(i32),
+    Long(i64),
+    Float(f32),
+    Double(f64),
+    ByteArray(Vec<u8>),
+    String(String),
+    List(Vec<NbtValue>),
+    Compound(NbtCompound),
+    IntArray(Vec<i32>),
+    LongArray(Vec<i64>),
+}
+
+#[derive(Debug, Clone, Default, PartialEq)]
+pub struct NbtCompound {
+    pub name: String,
+    pub tags: Vec<(String, NbtValue)>,
+}
+
+impl NbtCompound {
+    pub fn new(name: &str) -> Self {
+        Self {
+            name: name.to_string(),
+            tags: Vec::new(),
+        }
+    }
+
+    pub fn insert(&mut self, name: &str, value: NbtValue) {
+        self.tags.retain(|(n, _)| n != name);
+        self.tags.push((name.to_string(), value));
+    }
+
+    pub fn get(&self, name: &str) -> Option<&NbtValue> {
+        self.tags.iter().find(|(n, _)| n == name).map(|(_, v)| v)
+    }
+
+    pub fn get_mut(&mut self, name: &str) -> Option<&mut NbtValue> {
+        self.tags.iter_mut().find(|(n, _)| n == name).map(|(_, v)| v)
+    }
+
+    pub fn contains(&self, name: &str) -> bool {
+        self.tags.iter().any(|(n, _)| n == name)
+    }
+
+    pub fn remove(&mut self, name: &str) {
+        self.tags.retain(|(n, _)| n != name);
+    }
+
+    pub fn compound(&self, name: &str) -> Option<&NbtCompound> {
+        self.get(name).and_then(|v| match v {
+            NbtValue::Compound(c) => Some(c),
+            _ => None,
+        })
+    }
+
+    pub fn compound_mut(&mut self, name: &str) -> Option<&mut NbtCompound> {
+        self.get_mut(name).and_then(|v| match v {
+            NbtValue::Compound(c) => Some(c),
+            _ => None,
+        })
+    }
+
+    pub fn byte(&self, name: &str) -> Option<i8> {
+        self.get(name).and_then(|v| match v {
+            NbtValue::Byte(b) => Some(*b),
+            _ => None,
+        })
+    }
+
+    pub fn short(&self, name: &str) -> Option<i16> {
+        self.get(name).and_then(|v| match v {
+            NbtValue::Short(s) => Some(*s),
+            _ => None,
+        })
+    }
+
+    pub fn int(&self, name: &str) -> Option<i32> {
+        self.get(name).and_then(|v| match v {
+            NbtValue::Int(i) => Some(*i),
+            _ => None,
+        })
+    }
+
+    pub fn long(&self, name: &str) -> Option<i64> {
+        self.get(name).and_then(|v| match v {
+            NbtValue::Long(l) => Some(*l),
+            _ => None,
+        })
+    }
+
+    pub fn float(&self, name: &str) -> Option<f32> {
+        self.get(name).and_then(|v| match v {
+            NbtValue::Float(f) => Some(*f),
+            _ => None,
+        })
+    }
+
+    pub fn double(&self, name: &str) -> Option<f64> {
+        self.get(name).and_then(|v| match v {
+            NbtValue::Double(d) => Some(*d),
+            _ => None,
+        })
+    }
+
+    pub fn string(&self, name: &str) -> Option<&str> {
+        self.get(name).and_then(|v| match v {
+            NbtValue::String(s) => Some(s.as_str()),
+            _ => None,
+        })
+    }
+
+    pub fn byte_array(&self, name: &str) -> Option<&[u8]> {
+        self.get(name).and_then(|v| match v {
+            NbtValue::ByteArray(b) => Some(b.as_slice()),
+            _ => None,
+        })
+    }
+
+    pub fn int_array(&self, name: &str) -> Option<&[i32]> {
+        self.get(name).and_then(|v| match v {
+            NbtValue::IntArray(a) => Some(a.as_slice()),
+            _ => None,
+        })
+    }
+
+    pub fn long_array(&self, name: &str) -> Option<&[i64]> {
+        self.get(name).and_then(|v| match v {
+            NbtValue::LongArray(a) => Some(a.as_slice()),
+            _ => None,
+        })
+    }
+
+    pub fn list(&self, name: &str) -> Option<&[NbtValue]> {
+        self.get(name).and_then(|v| match v {
+            NbtValue::List(l) => Some(l.as_slice()),
+            _ => None,
+        })
+    }
+
+    pub fn list_compounds(&self, name: &str) -> Vec<&NbtCompound> {
+        self.list(name)
+            .unwrap_or(&[])
+            .iter()
+            .filter_map(|v| match v {
+                NbtValue::Compound(c) => Some(c),
+                _ => None,
+            })
+            .collect()
+    }
+}
+
+fn tag_type_id(v: &NbtValue) -> u8 {
+    match v {
+        NbtValue::Byte(_) => 1,
+        NbtValue::Short(_) => 2,
+        NbtValue::Int(_) => 3,
+        NbtValue::Long(_) => 4,
+        NbtValue::Float(_) => 5,
+        NbtValue::Double(_) => 6,
+        NbtValue::ByteArray(_) => 7,
+        NbtValue::String(_) => 8,
+        NbtValue::List(_) => 9,
+        NbtValue::Compound(_) => 10,
+        NbtValue::IntArray(_) => 11,
+        NbtValue::LongArray(_) => 12,
+    }
+}
+
+fn read_be_i16(data: &[u8], off: usize) -> i16 {
+    i16::from_be_bytes([data[off], data[off + 1]])
+}
+
+fn read_be_i32(data: &[u8], off: usize) -> i32 {
+    i32::from_be_bytes([data[off], data[off + 1], data[off + 2], data[off + 3]])
+}
+
+fn read_be_i64(data: &[u8], off: usize) -> i64 {
+    i64::from_be_bytes([
+        data[off],
+        data[off + 1],
+        data[off + 2],
+        data[off + 3],
+        data[off + 4],
+        data[off + 5],
+        data[off + 6],
+        data[off + 7],
+    ])
+}
+
+fn read_be_f32(data: &[u8], off: usize) -> f32 {
+    f32::from_be_bytes([data[off], data[off + 1], data[off + 2], data[off + 3]])
+}
+
+fn read_be_f64(data: &[u8], off: usize) -> f64 {
+    f64::from_be_bytes([
+        data[off],
+        data[off + 1],
+        data[off + 2],
+        data[off + 3],
+        data[off + 4],
+        data[off + 5],
+        data[off + 6],
+        data[off + 7],
+    ])
+}
+
+fn read_string(data: &[u8], off: usize) -> Result<(String, usize), String> {
+    let len = read_be_i16(data, off) as usize;
+    let start = off + 2;
+    if start + len > data.len() {
+        return Err("string extends past end of data".into());
+    }
+    let s = String::from_utf8_lossy(&data[start..start + len]).to_string();
+    Ok((s, start + len))
+}
+
+pub fn read_nbt(data: &[u8]) -> Result<NbtCompound, String> {
+    if data.is_empty() {
+        return Err("empty NBT data".into());
+    }
+    let mut pos = 0;
+    let tag_type = data[pos];
+    pos += 1;
+    if tag_type != 10 {
+        return Err(format!("root tag is not compound (type={})", tag_type));
+    }
+    let (name, new_pos) = read_string(data, pos)?;
+    pos = new_pos;
+    let (compound, _new_pos) = read_compound_payload(data, pos)?;
+    let mut result = compound;
+    result.name = name;
+    Ok(result)
+}
+
+fn read_compound_payload(data: &[u8], mut pos: usize) -> Result<(NbtCompound, usize), String> {
+    let mut compound = NbtCompound::default();
+    loop {
+        if pos >= data.len() {
+            return Err("unexpected end in compound".into());
+        }
+        let tag_type = data[pos];
+        pos += 1;
+        if tag_type == 0 {
+            break;
+        }
+        let (name, new_pos) = read_string(data, pos)?;
+        pos = new_pos;
+        let (value, new_pos) = read_value(data, pos, tag_type)?;
+        pos = new_pos;
+        compound.tags.push((name, value));
+    }
+    Ok((compound, pos))
+}
+
+fn read_value(data: &[u8], pos: usize, tag_type: u8) -> Result<(NbtValue, usize), String> {
+    match tag_type {
+        1 => Ok((NbtValue::Byte(data[pos] as i8), pos + 1)),
+        2 => Ok((NbtValue::Short(read_be_i16(data, pos)), pos + 2)),
+        3 => Ok((NbtValue::Int(read_be_i32(data, pos)), pos + 4)),
+        4 => Ok((NbtValue::Long(read_be_i64(data, pos)), pos + 8)),
+        5 => Ok((NbtValue::Float(read_be_f32(data, pos)), pos + 4)),
+        6 => Ok((NbtValue::Double(read_be_f64(data, pos)), pos + 8)),
+        7 => {
+            let len = read_be_i32(data, pos) as usize;
+            let start = pos + 4;
+            if start + len > data.len() {
+                return Err("byte array extends past end".into());
+            }
+            Ok((NbtValue::ByteArray(data[start..start + len].to_vec()), start + len))
+        }
+        8 => {
+            let (s, new_pos) = read_string(data, pos)?;
+            Ok((NbtValue::String(s), new_pos))
+        }
+        9 => {
+            let elem_type = data[pos];
+            let count = read_be_i32(data, pos + 1) as usize;
+            let mut list_pos = pos + 5;
+            let mut list = Vec::with_capacity(count);
+            for _ in 0..count {
+                let (val, new_pos) = read_value(data, list_pos, elem_type)?;
+                list_pos = new_pos;
+                list.push(val);
+            }
+            Ok((NbtValue::List(list), list_pos))
+        }
+        10 => {
+            let (compound, new_pos) = read_compound_payload(data, pos)?;
+            Ok((NbtValue::Compound(compound), new_pos))
+        }
+        11 => {
+            let len = read_be_i32(data, pos) as usize;
+            let start = pos + 4;
+            let mut arr = Vec::with_capacity(len);
+            for i in 0..len {
+                let off = start + i * 4;
+                if off + 4 > data.len() {
+                    return Err("int array extends past end".into());
+                }
+                arr.push(read_be_i32(data, off));
+            }
+            Ok((NbtValue::IntArray(arr), start + len * 4))
+        }
+        12 => {
+            let len = read_be_i32(data, pos) as usize;
+            let start = pos + 4;
+            let mut arr = Vec::with_capacity(len);
+            for i in 0..len {
+                let off = start + i * 8;
+                if off + 8 > data.len() {
+                    return Err("long array extends past end".into());
+                }
+                arr.push(read_be_i64(data, off));
+            }
+            Ok((NbtValue::LongArray(arr), start + len * 8))
+        }
+        _ => Err(format!("unknown NBT tag type: {}", tag_type)),
+    }
+}
+
+pub fn write_nbt(compound: &NbtCompound) -> Vec<u8> {
+    let mut out = Vec::new();
+    out.push(10);
+    write_string(&mut out, &compound.name);
+    write_compound_payload(&mut out, compound);
+    out.push(0);
+    out
+}
+
+fn write_string(out: &mut Vec<u8>, s: &str) {
+    let bytes = s.as_bytes();
+    let len = (bytes.len() as i16).to_be_bytes();
+    out.extend_from_slice(&len);
+    out.extend_from_slice(bytes);
+}
+
+fn write_compound_payload(out: &mut Vec<u8>, compound: &NbtCompound) {
+    for (name, value) in &compound.tags {
+        out.push(tag_type_id(value));
+        write_string(out, name);
+        write_value(out, value);
+    }
+}
+
+fn write_value(out: &mut Vec<u8>, value: &NbtValue) {
+    match value {
+        NbtValue::Byte(b) => out.push(*b as u8),
+        NbtValue::Short(s) => out.extend_from_slice(&s.to_be_bytes()),
+        NbtValue::Int(i) => out.extend_from_slice(&i.to_be_bytes()),
+        NbtValue::Long(l) => out.extend_from_slice(&l.to_be_bytes()),
+        NbtValue::Float(f) => out.extend_from_slice(&f.to_be_bytes()),
+        NbtValue::Double(d) => out.extend_from_slice(&d.to_be_bytes()),
+        NbtValue::ByteArray(arr) => {
+            out.extend_from_slice(&(arr.len() as i32).to_be_bytes());
+            out.extend_from_slice(arr);
+        }
+        NbtValue::String(s) => write_string(out, s),
+        NbtValue::List(list) => {
+            let elem_type = list.first().map(|v| tag_type_id(v)).unwrap_or(0);
+            out.push(elem_type);
+            out.extend_from_slice(&(list.len() as i32).to_be_bytes());
+            for item in list {
+                write_value(out, item);
+            }
+        }
+        NbtValue::Compound(c) => {
+            write_compound_payload(out, c);
+            out.push(0);
+        }
+        NbtValue::IntArray(arr) => {
+            out.extend_from_slice(&(arr.len() as i32).to_be_bytes());
+            for i in arr {
+                out.extend_from_slice(&i.to_be_bytes());
+            }
+        }
+        NbtValue::LongArray(arr) => {
+            out.extend_from_slice(&(arr.len() as i32).to_be_bytes());
+            for l in arr {
+                out.extend_from_slice(&l.to_be_bytes());
+            }
+        }
+    }
+}
+
+pub fn read_gzip_nbt(data: &[u8]) -> Result<NbtCompound, String> {
+    let mut decoder = GzDecoder::new(data);
+    let mut buf = Vec::new();
+    decoder
+        .read_to_end(&mut buf)
+        .map_err(|e| format!("gzip decompress failed: {}", e))?;
+    read_nbt(&buf)
+}
+
+pub fn write_gzip_nbt(compound: &NbtCompound) -> Vec<u8> {
+    let raw = write_nbt(compound);
+    let mut encoder = GzEncoder::new(Vec::new(), Compression::best());
+    encoder.write_all(&raw).unwrap();
+    encoder.finish().unwrap()
+}
+
+pub fn read_zlib_nbt(data: &[u8]) -> Result<NbtCompound, String> {
+    use flate2::read::ZlibDecoder;
+    let mut decoder = ZlibDecoder::new(data);
+    let mut buf = Vec::new();
+    decoder
+        .read_to_end(&mut buf)
+        .map_err(|e| format!("zlib decompress failed: {}", e))?;
+    read_nbt(&buf)
+}
+
+pub fn write_zlib_nbt(compound: &NbtCompound) -> Vec<u8> {
+    use flate2::write::ZlibEncoder;
+    let raw = write_nbt(compound);
+    let mut encoder = ZlibEncoder::new(Vec::new(), Compression::best());
+    encoder.write_all(&raw).unwrap();
+    encoder.finish().unwrap()
+}
+
+pub fn get_byte_array_or(compound: &NbtCompound, name: &str, default_len: usize) -> Vec<u8> {
+    compound
+        .byte_array(name)
+        .map(|b| {
+            let mut v = b.to_vec();
+            if v.len() < default_len {
+                v.resize(default_len, 0);
+            }
+            v
+        })
+        .unwrap_or_else(|| vec![0u8; default_len])
+}
+
+pub fn get_int_array_or(compound: &NbtCompound, name: &str, default_len: usize) -> Vec<i32> {
+    compound
+        .int_array(name)
+        .map(|a| {
+            let mut v = a.to_vec();
+            if v.len() < default_len {
+                v.resize(default_len, 0);
+            }
+            v
+        })
+        .unwrap_or_else(|| vec![0i32; default_len])
+}
+
+pub fn get_long_array_or(compound: &NbtCompound, name: &str, default_len: usize) -> Vec<i64> {
+    compound
+        .long_array(name)
+        .map(|a| {
+            let mut v = a.to_vec();
+            if v.len() < default_len {
+                v.resize(default_len, 0);
+            }
+            v
+        })
+        .unwrap_or_else(|| vec![0i64; default_len])
+}
+
+pub fn get_nibble(data: &[u8], index: usize) -> u8 {
+    let byte_index = index >> 1;
+    if byte_index >= data.len() {
+        return 0;
+    }
+    let b = data[byte_index];
+    if index & 1 == 0 {
+        b & 0x0F
+    } else {
+        (b >> 4) & 0x0F
+    }
+}
+
+pub fn set_nibble(data: &mut [u8], index: usize, value: u8) {
+    let byte_index = index >> 1;
+    if byte_index >= data.len() {
+        return;
+    }
+    let val = value & 0x0F;
+    if index & 1 == 0 {
+        data[byte_index] = (data[byte_index] & 0xF0) | val;
+    } else {
+        data[byte_index] = (data[byte_index] & 0x0F) | (val << 4);
+    }
+}
+
+pub fn clone_or_empty_list(compound: &NbtCompound, name: &str) -> Vec<NbtValue> {
+    compound
+        .list(name)
+        .map(|l| l.to_vec())
+        .unwrap_or_default()
+}
diff --git a/src-tauri/src/commands/java2lce/payload.rs b/src-tauri/src/commands/java2lce/payload.rs
new file mode 100644
index 0000000..5238467
--- /dev/null
+++ b/src-tauri/src/commands/java2lce/payload.rs
@@ -0,0 +1,683 @@
+use super::nbt;
+const SAVE_FILE_VERSION_COMPRESSED_CHUNK_STORAGE: i16 = 8;
+const SAVE_FILE_VERSION_CHUNK_INHABITED_TIME: i16 = 9;
+const COMPRESSED_CHUNK_SECTION_HEIGHT: usize = 128;
+const BLOCKS_PER_SECTION: usize = COMPRESSED_CHUNK_SECTION_HEIGHT * 16 * 16;
+const NIBBLES_PER_SECTION: usize = BLOCKS_PER_SECTION / 2;
+const FULL_CHUNK_BLOCKS: usize = 256 * 16 * 16;
+const FULL_CHUNK_NIBBLES: usize = FULL_CHUNK_BLOCKS / 2;
+const INDEX_TYPE_MASK: u16 = 0x0003;
+const INDEX_TYPE_1BIT: u16 = 0x0000;
+const INDEX_TYPE_2BIT: u16 = 0x0001;
+const INDEX_TYPE_4BIT: u16 = 0x0002;
+const INDEX_TYPE_0_OR_8BIT: u16 = 0x0003;
+const INDEX_TYPE_0BIT_FLAG: u16 = 0x0004;
+const SPARSE_ALL_ZERO_INDEX: u8 = 128;
+const SPARSE_ALL_FIFTEEN_INDEX: u8 = 129;
+fn read_be_i16(data: &[u8], off: usize) -> i16 {
+    i16::from_be_bytes([data[off], data[off + 1]])
+}
+
+fn read_be_i32(data: &[u8], off: usize) -> i32 {
+    i32::from_be_bytes([data[off], data[off + 1], data[off + 2], data[off + 3]])
+}
+
+fn read_be_i64(data: &[u8], off: usize) -> i64 {
+    i64::from_be_bytes([
+        data[off], data[off + 1], data[off + 2], data[off + 3], data[off + 4], data[off + 5],
+        data[off + 6], data[off + 7],
+    ])
+}
+
+fn write_be_i16(out: &mut Vec<u8>, v: i16) {
+    out.extend_from_slice(&v.to_be_bytes());
+}
+
+fn write_be_i32(out: &mut Vec<u8>, v: i32) {
+    out.extend_from_slice(&v.to_be_bytes());
+}
+
+fn write_be_i64(out: &mut Vec<u8>, v: i64) {
+    out.extend_from_slice(&v.to_be_bytes());
+}
+
+fn get_compressed_tile_index(block: usize, tile: usize) -> usize {
+    let mut index = ((block & 0x180) << 6) | ((block & 0x060) << 4) | ((block & 0x01F) << 2);
+    index |= ((tile & 0x30) << 7) | ((tile & 0x0C) << 5) | (tile & 0x03);
+    index
+}
+
+fn get_nibble_value(nibble_data: &[u8], xz: usize, y: usize) -> u8 {
+    let pos = (xz << 7) | y;
+    let slot = pos >> 1;
+    let part = pos & 1;
+    if slot >= nibble_data.len() {
+        return 0;
+    }
+    let b = nibble_data[slot];
+    if part == 0 {
+        b & 0x0F
+    } else {
+        (b >> 4) & 0x0F
+    }
+}
+
+fn set_nibble_value(nibble_data: &mut [u8], xz: usize, y: usize, value: u8) {
+    let pos = (xz << 7) | y;
+    let slot = pos >> 1;
+    let part = pos & 1;
+    if slot >= nibble_data.len() {
+        return;
+    }
+    let val = value & 0x0F;
+    if part == 0 {
+        nibble_data[slot] = (nibble_data[slot] & 0xF0) | val;
+    } else {
+        nibble_data[slot] = (nibble_data[slot] & 0x0F) | (val << 4);
+    }
+}
+
+fn ensure_length(input: &[u8], expected_len: usize) -> Vec<u8> {
+    if input.len() == expected_len {
+        return input.to_vec();
+    }
+    let mut v = vec![0u8; expected_len];
+    let copy_len = input.len().min(expected_len);
+    v[..copy_len].copy_from_slice(&input[..copy_len]);
+    v
+}
+
+fn extract_lower_block_section(full_blocks: &[u8]) -> Vec<u8> {
+    if full_blocks.len() == BLOCKS_PER_SECTION {
+        return full_blocks.to_vec();
+    }
+    let mut lower = vec![0u8; BLOCKS_PER_SECTION];
+    for xz in 0..256 {
+        let src_start = xz * 256;
+        let dst_start = xz * COMPRESSED_CHUNK_SECTION_HEIGHT;
+        let copy_len = COMPRESSED_CHUNK_SECTION_HEIGHT.min(full_blocks.len() - src_start.min(full_blocks.len()));
+        if src_start + copy_len <= full_blocks.len() && dst_start + copy_len <= BLOCKS_PER_SECTION {
+            lower[dst_start..dst_start + copy_len]
+                .copy_from_slice(&full_blocks[src_start..src_start + copy_len]);
+        }
+    }
+    lower
+}
+
+fn extract_upper_block_section(full_blocks: &[u8]) -> Vec<u8> {
+    if full_blocks.len() < FULL_CHUNK_BLOCKS {
+        return vec![0u8; BLOCKS_PER_SECTION];
+    }
+    let mut upper = vec![0u8; BLOCKS_PER_SECTION];
+    for xz in 0..256 {
+        let src_start = xz * 256 + COMPRESSED_CHUNK_SECTION_HEIGHT;
+        let dst_start = xz * COMPRESSED_CHUNK_SECTION_HEIGHT;
+        upper[dst_start..dst_start + COMPRESSED_CHUNK_SECTION_HEIGHT].copy_from_slice(&full_blocks[src_start..src_start + COMPRESSED_CHUNK_SECTION_HEIGHT]);
+    }
+    upper
+}
+
+fn extract_lower_nibble_section(full_nibbles: &[u8]) -> Vec<u8> {
+    let nibble_height = COMPRESSED_CHUNK_SECTION_HEIGHT / 2;
+    if full_nibbles.len() == NIBBLES_PER_SECTION {
+        return full_nibbles.to_vec();
+    }
+    let mut lower = vec![0u8; NIBBLES_PER_SECTION];
+    for xz in 0..256 {
+        let src_start = xz * nibble_height * 2;
+        let dst_start = xz * nibble_height;
+        let copy_len = nibble_height.min(
+            full_nibbles.len().saturating_sub(src_start),
+        );
+        if copy_len > 0 {
+            lower[dst_start..dst_start + copy_len].copy_from_slice(&full_nibbles[src_start..src_start + copy_len]);
+        }
+    }
+    lower
+}
+
+fn extract_upper_nibble_section(full_nibbles: &[u8]) -> Vec<u8> {
+    let nibble_height = COMPRESSED_CHUNK_SECTION_HEIGHT / 2;
+    if full_nibbles.len() < FULL_CHUNK_NIBBLES {
+        return vec![0u8; NIBBLES_PER_SECTION];
+    }
+    let mut upper = vec![0u8; NIBBLES_PER_SECTION];
+    for xz in 0..256 {
+        let src_start = xz * nibble_height * 2 + nibble_height;
+        let dst_start = xz * nibble_height;
+        upper[dst_start..dst_start + nibble_height]
+            .copy_from_slice(&full_nibbles[src_start..src_start + nibble_height]);
+    }
+    upper
+}
+
+fn combine_block_sections(lower: &[u8], upper: &[u8]) -> Vec<u8> {
+    if lower.len() == FULL_CHUNK_BLOCKS {
+        return lower.to_vec();
+    }
+    let mut combined = vec![0u8; FULL_CHUNK_BLOCKS];
+    for xz in 0..256 {
+        let lower_start = xz * COMPRESSED_CHUNK_SECTION_HEIGHT;
+        let out_start = xz * 256;
+        let copy_len = COMPRESSED_CHUNK_SECTION_HEIGHT.min(lower.len().saturating_sub(lower_start));
+        if copy_len > 0 {
+            combined[out_start..out_start + copy_len].copy_from_slice(&lower[lower_start..lower_start + copy_len]);
+        }
+        let upper_start = xz * COMPRESSED_CHUNK_SECTION_HEIGHT;
+        let out_upper = out_start + COMPRESSED_CHUNK_SECTION_HEIGHT;
+        let copy_len2 = COMPRESSED_CHUNK_SECTION_HEIGHT.min(upper.len().saturating_sub(upper_start));
+        if copy_len2 > 0 {
+            combined[out_upper..out_upper + copy_len2]
+                .copy_from_slice(&upper[upper_start..upper_start + copy_len2]);
+        }
+    }
+    combined
+}
+
+fn combine_nibble_sections(lower: &[u8], upper: &[u8]) -> Vec<u8> {
+    let nibble_height = COMPRESSED_CHUNK_SECTION_HEIGHT / 2;
+    if lower.len() == FULL_CHUNK_NIBBLES {
+        return lower.to_vec();
+    }
+    let mut combined = vec![0u8; FULL_CHUNK_NIBBLES];
+    for xz in 0..256 {
+        let lower_start = xz * nibble_height;
+        let out_start = xz * nibble_height * 2;
+        let copy_len = nibble_height.min(lower.len().saturating_sub(lower_start));
+        if copy_len > 0 {
+            combined[out_start..out_start + copy_len]
+                .copy_from_slice(&lower[lower_start..lower_start + copy_len]);
+        }
+        let upper_start = xz * nibble_height;
+        let out_upper = out_start + nibble_height;
+        let copy_len2 = nibble_height.min(upper.len().saturating_sub(upper_start));
+        if copy_len2 > 0 {
+            combined[out_upper..out_upper + copy_len2]
+                .copy_from_slice(&upper[upper_start..upper_start + copy_len2]);
+        }
+    }
+    combined
+}
+
+pub fn encode_legacy_nbt(level: &nbt::NbtCompound) -> Vec<u8> {
+    let mut root = nbt::NbtCompound::new("");
+    root.insert("Level", nbt::NbtValue::Compound(level.clone()));
+    nbt::write_nbt(&root)
+}
+
+fn write_compressed_tile_storage(out: &mut Vec<u8>, blocks: &[u8]) {
+    let normalized = ensure_length(blocks, BLOCKS_PER_SECTION);
+    let mut blob = vec![0u8; 1024 + BLOCKS_PER_SECTION];
+    let mut data_offset: usize = 0;
+    for block in 0..512 {
+        let index = (INDEX_TYPE_0_OR_8BIT | ((data_offset as u16) << 1)) as u16;
+        blob[block * 2..block * 2 + 2].copy_from_slice(&index.to_le_bytes());
+        for tile in 0..64 {
+            blob[1024 + data_offset + tile] = normalized[get_compressed_tile_index(block, tile)];
+        }
+        data_offset += 64;
+    }
+
+    write_be_i32(out, blob.len() as i32);
+    out.extend_from_slice(&blob);
+}
+
+fn write_empty_compressed_tile_storage(out: &mut Vec<u8>) {
+    let mut blob = vec![0u8; 1024];
+    for block in 0..512 {
+        let index = (INDEX_TYPE_0_OR_8BIT | INDEX_TYPE_0BIT_FLAG) as u16;
+        blob[block * 2..block * 2 + 2].copy_from_slice(&index.to_le_bytes());
+    }
+    write_be_i32(out, blob.len() as i32);
+    out.extend_from_slice(&blob);
+}
+
+fn write_sparse_nibble_storage(out: &mut Vec<u8>, nibble_data: &[u8], supports_all_fifteen: bool) {
+    let normalized = ensure_length(nibble_data, NIBBLES_PER_SECTION);
+    let mut plane_indices = [0u8; 128];
+    let mut planes: Vec<Vec<u8>> = Vec::new();
+    for y in 0..128 {
+        let mut all_zero = true;
+        let mut all_fifteen = supports_all_fifteen;
+        let mut plane = vec![0u8; 128];
+        let mut plane_cursor = 0;
+        for xz in 0..128 {
+            let first = get_nibble_value(&normalized, xz * 2, y);
+            let second = get_nibble_value(&normalized, xz * 2 + 1, y);
+
+            if first != 0 || second != 0 {
+                all_zero = false;
+            }
+            if supports_all_fifteen && (first != 15 || second != 15) {
+                all_fifteen = false;
+            }
+
+            plane[plane_cursor] = first | (second << 4);
+            plane_cursor += 1;
+        }
+
+        if all_zero {
+            plane_indices[y] = SPARSE_ALL_ZERO_INDEX;
+            continue;
+        }
+        if supports_all_fifteen && all_fifteen {
+            plane_indices[y] = SPARSE_ALL_FIFTEEN_INDEX;
+            continue;
+        }
+
+        plane_indices[y] = planes.len() as u8;
+        planes.push(plane);
+    }
+
+    write_be_i32(out, planes.len() as i32);
+    out.extend_from_slice(&plane_indices);
+    for plane in &planes {
+        out.extend_from_slice(plane);
+    }
+}
+
+fn write_empty_sparse_nibble_storage(out: &mut Vec<u8>, supports_all_fifteen: bool, fill_with_fifteen: bool) {
+    write_be_i32(out, 0);
+    let fill = if supports_all_fifteen && fill_with_fifteen {
+        SPARSE_ALL_FIFTEEN_INDEX
+    } else {
+        SPARSE_ALL_ZERO_INDEX
+    };
+    let plane_indices = [fill; 128];
+    out.extend_from_slice(&plane_indices);
+}
+
+pub fn encode_compressed_storage(level: &nbt::NbtCompound) -> Vec<u8> {
+    let blocks = level.byte_array("Blocks").unwrap_or(&[]);
+    let data = level.byte_array("Data").unwrap_or(&[]);
+    let sky_light_raw = level.byte_array("SkyLight").unwrap_or(&[]);
+    let block_light_raw = level.byte_array("BlockLight").unwrap_or(&[]);
+    let height_map = level.byte_array("HeightMap").unwrap_or(&[]);
+    let biomes = level.byte_array("Biomes").unwrap_or(&[]);
+    let default_sky = vec![0xFF; NIBBLES_PER_SECTION];
+    let default_light = vec![0u8; NIBBLES_PER_SECTION];
+    let sky_light = if sky_light_raw.is_empty() { default_sky.as_slice() } else { sky_light_raw };
+    let block_light = if block_light_raw.is_empty() { default_light.as_slice() } else { block_light_raw };
+    let mut out = Vec::new();
+    write_be_i16(&mut out, SAVE_FILE_VERSION_CHUNK_INHABITED_TIME);
+    write_be_i32(&mut out, level.int("xPos").unwrap_or(0));
+    write_be_i32(&mut out, level.int("zPos").unwrap_or(0));
+    write_be_i64(&mut out, level.long("LastUpdate").unwrap_or(0));
+    write_be_i64(&mut out, level.long("InhabitedTime").unwrap_or(0));
+    write_compressed_tile_storage(&mut out, &extract_lower_block_section(blocks));
+    write_compressed_tile_storage(&mut out, &extract_upper_block_section(blocks));
+    write_sparse_nibble_storage(&mut out, &extract_lower_nibble_section(data), false);
+    write_sparse_nibble_storage(&mut out, &extract_upper_nibble_section(data), false);
+    write_sparse_nibble_storage(&mut out, &extract_lower_nibble_section(sky_light), true);
+    write_sparse_nibble_storage(&mut out, &extract_upper_nibble_section(sky_light), true);
+    write_sparse_nibble_storage(&mut out, &extract_lower_nibble_section(block_light), true);
+    write_sparse_nibble_storage(&mut out, &extract_upper_nibble_section(block_light), true);
+    let hm = ensure_length(height_map, 256);
+    out.extend_from_slice(&hm[..256]);
+    write_be_i16(&mut out, level.short("TerrainPopulatedFlags").unwrap_or(0));
+    let bio = ensure_length(biomes, 256);
+    out.extend_from_slice(&bio[..256]);
+    let dynamic_root = nbt::NbtCompound::new("");
+    let dynamic_bytes = nbt::write_nbt(&dynamic_root);
+    out.extend_from_slice(&dynamic_bytes);
+    out
+}
+
+fn is_compressed_chunk_storage(data: &[u8]) -> bool {
+    if data.len() < 2 + 4 + 4 + 8 {
+        return false;
+    }
+    let version = read_be_i16(data, 0);
+    version == SAVE_FILE_VERSION_COMPRESSED_CHUNK_STORAGE || version == SAVE_FILE_VERSION_CHUNK_INHABITED_TIME
+}
+
+pub fn try_read_chunk_coordinates(
+    data: &[u8],
+) -> Option<(i32, i32, bool)> {
+    if let Some((cx, cz, wrapped)) = try_read_legacy_level_coords(data) {
+        return Some((cx, cz, wrapped));
+    }
+
+    if is_compressed_chunk_storage(data) {
+        let cx = read_be_i32(data, 2);
+        let cz = read_be_i32(data, 6);
+        return Some((cx, cz, false));
+    }
+
+    None
+}
+
+fn try_read_legacy_level_coords(data: &[u8]) -> Option<(i32, i32, bool)> {
+    if data.is_empty() || data[0] != 10 {
+        return None;
+    }
+    let compound = nbt::read_nbt(data).ok()?;
+    let (level, has_wrapper) = if let Some(nbt::NbtValue::Compound(c)) = compound.get("Level") {
+        (c, true)
+    } else {
+        (&compound, false)
+    };
+    let cx = level.int("xPos")?;
+    let cz = level.int("zPos")?;
+    Some((cx, cz, has_wrapper))
+}
+
+pub fn force_chunk_coordinates(data: &[u8], expected_x: i32, expected_z: i32) -> Vec<u8> {
+    if data.is_empty() {
+        return Vec::new();
+    }
+
+    if let Ok((mut level, _)) = read_legacy_level(data) {
+        level.insert("xPos", nbt::NbtValue::Int(expected_x));
+        level.insert("zPos", nbt::NbtValue::Int(expected_z));
+        return encode_legacy_nbt(&level);
+    }
+
+    if is_compressed_chunk_storage(data) {
+        let mut patched = data.to_vec();
+        patched[2..6].copy_from_slice(&expected_x.to_be_bytes());
+        patched[6..10].copy_from_slice(&expected_z.to_be_bytes());
+        return patched;
+    }
+
+    Vec::new()
+}
+
+fn read_compressed_tile_storage(data: &[u8], offset: &mut usize) -> Result<Vec<u8>, String> {
+    let allocated_size = read_be_i32(data, *offset) as usize;
+    *offset += 4;
+    if allocated_size < 1024 || *offset + allocated_size > data.len() {
+        return Err("Invalid CompressedTileStorage payload.".into());
+    }
+
+    let blob = &data[*offset..*offset + allocated_size];
+    *offset += allocated_size;
+    let data_region = &blob[1024..];
+    let mut blocks = vec![0u8; BLOCKS_PER_SECTION];
+    for block in 0..512 {
+        let block_index = u16::from_le_bytes([blob[block * 2], blob[block * 2 + 1]]);
+        let index_type = block_index & INDEX_TYPE_MASK;
+        if index_type == INDEX_TYPE_0_OR_8BIT {
+            if (block_index & INDEX_TYPE_0BIT_FLAG) != 0 {
+                let value = ((block_index >> 8) & 0xFF) as u8;
+                for tile in 0..64 {
+                    blocks[get_compressed_tile_index(block, tile)] = value;
+                }
+            } else {
+                let data_offset = ((block_index >> 1) & 0x7FFE) as usize;
+                if data_offset + 64 > data_region.len() {
+                    return Err("Invalid 8-bit CompressedTileStorage offset.".into());
+                }
+                for tile in 0..64 {
+                    blocks[get_compressed_tile_index(block, tile)] = data_region[data_offset + tile];
+                }
+            }
+            continue;
+        }
+
+        let bits_per_tile = match index_type {
+            INDEX_TYPE_1BIT => 1,
+            INDEX_TYPE_2BIT => 2,
+            INDEX_TYPE_4BIT => 4,
+            _ => return Err("Unsupported CompressedTileStorage index type.".into()),
+        };
+
+        let tile_type_count = 1usize << bits_per_tile;
+        let tile_type_mask = (tile_type_count - 1) as u8;
+        let index_shift = 3 - index_type as usize;
+        let index_mask_bits = (7 >> index_type) as usize;
+        let index_mask_bytes = (62 >> index_shift) as usize;
+        let packed_data_size = (8usize << index_type) as usize;
+        let data_offset_packed = ((block_index >> 1) & 0x7FFE) as usize;
+        if data_offset_packed + tile_type_count + packed_data_size > data_region.len() {
+            return Err("Invalid packed CompressedTileStorage offset.".into());
+        }
+
+        let tile_types = &data_region[data_offset_packed..data_offset_packed + tile_type_count];
+        let packed = &data_region[data_offset_packed + tile_type_count..data_offset_packed + tile_type_count + packed_data_size];
+        for tile in 0..64 {
+            let idx = (tile >> index_shift) & index_mask_bytes;
+            let bit = (tile & index_mask_bits) * bits_per_tile;
+            let palette_index = (packed[idx] >> bit) & tile_type_mask;
+            blocks[get_compressed_tile_index(block, tile)] = tile_types[palette_index as usize];
+        }
+    }
+
+    Ok(blocks)
+}
+
+fn skip_compressed_tile_storage(data: &[u8], offset: &mut usize) -> Result<(), String> {
+    let allocated_size = read_be_i32(data, *offset) as usize;
+    *offset += 4;
+    if *offset + allocated_size > data.len() {
+        return Err("Invalid CompressedTileStorage payload.".into());
+    }
+    *offset += allocated_size;
+    Ok(())
+}
+
+fn read_sparse_nibble_storage(data: &[u8], offset: &mut usize, supports_all_fifteen: bool) -> Result<Vec<u8>, String> {
+    let count = read_be_i32(data, *offset) as usize;
+    *offset += 4;
+    let storage_bytes = 128 + count * 128;
+    if count > data.len() || *offset + storage_bytes > data.len() {
+        return Err("Invalid SparseStorage payload.".into());
+    }
+
+    let blob = &data[*offset..*offset + storage_bytes];
+    *offset += storage_bytes;
+    let plane_indices = &blob[..128];
+    let plane_data = &blob[128..];
+    let mut nibble_data = vec![0u8; NIBBLES_PER_SECTION];
+    for y in 0..128 {
+        let plane_index = plane_indices[y];
+        if plane_index == SPARSE_ALL_ZERO_INDEX {
+            continue;
+        }
+        if supports_all_fifteen && plane_index == SPARSE_ALL_FIFTEEN_INDEX {
+            for xz in 0..256 {
+                set_nibble_value(&mut nibble_data, xz, y, 15);
+            }
+            continue;
+        }
+
+        let plane_offset = plane_index as usize * 128;
+        if plane_offset + 128 > plane_data.len() {
+            return Err("Invalid sparse plane index.".into());
+        }
+
+        let plane = &plane_data[plane_offset..plane_offset + 128];
+        for xz in 0..128 {
+            let packed = plane[xz];
+            set_nibble_value(&mut nibble_data, xz * 2, y, packed & 0x0F);
+            set_nibble_value(&mut nibble_data, xz * 2 + 1, y, (packed >> 4) & 0x0F);
+        }
+    }
+
+    Ok(nibble_data)
+}
+
+fn skip_sparse_nibble_storage(data: &[u8], offset: &mut usize) -> Result<(), String> {
+    let count = read_be_i32(data, *offset) as usize;
+    *offset += 4;
+    let storage_bytes = 128 + count * 128;
+    if count > data.len() || *offset + storage_bytes > data.len() {
+        return Err("Invalid SparseStorage payload.".into());
+    }
+    *offset += storage_bytes;
+    Ok(())
+}
+
+fn read_sized_bytes(data: &[u8], offset: &mut usize, length: usize) -> Vec<u8> {
+    let end = (*offset + length).min(data.len());
+    let result = data[*offset..end].to_vec();
+    *offset += length;
+    result
+}
+
+fn read_legacy_level(data: &[u8]) -> Result<(nbt::NbtCompound, bool), String> {
+    if data.is_empty() || data[0] != 10 {
+        return Err("Not NBT compound".into());
+    }
+    let file = nbt::read_nbt(data)?;
+    let has_level = file.get("Level").is_some();
+    let level = if let Some(nbt::NbtValue::Compound(c)) = file.get("Level") {
+        let mut cloned = c.clone();
+        cloned.name = "Level".to_string();
+        cloned
+    } else {
+        let mut cloned = file.clone();
+        cloned.name = "Level".to_string();
+        cloned
+    };
+    Ok((level, has_level))
+}
+
+pub fn try_decode_to_legacy_nbt(data: &[u8]) -> Option<Vec<u8>> {
+    if let Ok((mut level, _)) = read_legacy_level(data) {
+        level.name = "Level".to_string();
+        return Some(encode_legacy_nbt(&level));
+    }
+
+    if !is_compressed_chunk_storage(data) {
+        return None;
+    }
+
+    decode_compressed_chunk_to_legacy_root(data).ok().map(|root| nbt::write_nbt(&root))
+}
+
+fn decode_compressed_chunk_to_legacy_root(data: &[u8]) -> Result<nbt::NbtCompound, String> {
+    let mut offset = 0;
+    let version = read_be_i16(data, offset);
+    offset = 2;
+    if version != SAVE_FILE_VERSION_COMPRESSED_CHUNK_STORAGE
+        && version != SAVE_FILE_VERSION_CHUNK_INHABITED_TIME
+    {
+        return Err(format!("Unsupported compressed chunk version: {}", version));
+    }
+
+    let chunk_x = read_be_i32(data, offset);
+    offset += 4;
+    let chunk_z = read_be_i32(data, offset);
+    offset += 4;
+    let last_update = read_be_i64(data, offset);
+    offset += 8;
+    let inhabited_time = if version >= SAVE_FILE_VERSION_CHUNK_INHABITED_TIME {
+        let v = read_be_i64(data, offset);
+        offset += 8;
+        v
+    } else {
+        0
+    };
+
+    let lower_blocks = read_compressed_tile_storage(data, &mut offset)?;
+    let upper_blocks = read_compressed_tile_storage(data, &mut offset)?;
+    let lower_data = read_sparse_nibble_storage(data, &mut offset, false)?;
+    let upper_data = read_sparse_nibble_storage(data, &mut offset, false)?;
+    let lower_sky = read_sparse_nibble_storage(data, &mut offset, true)?;
+    let upper_sky = read_sparse_nibble_storage(data, &mut offset, true)?;
+    let lower_block_light = read_sparse_nibble_storage(data, &mut offset, true)?;
+    let upper_block_light = read_sparse_nibble_storage(data, &mut offset, true)?;
+    let height_map = read_sized_bytes(data, &mut offset, 256);
+    let terrain_populated_flags = read_be_i16(data, offset);
+    offset += 2;
+    let biomes = read_sized_bytes(data, &mut offset, 256);
+    let dynamic_root = if offset < data.len() {
+        nbt::read_nbt(&data[offset..]).unwrap_or_default()
+    } else {
+        nbt::NbtCompound::default()
+    };
+
+    let mut level = nbt::NbtCompound::new("Level");
+    level.insert("xPos", nbt::NbtValue::Int(chunk_x));
+    level.insert("zPos", nbt::NbtValue::Int(chunk_z));
+    level.insert("LastUpdate", nbt::NbtValue::Long(last_update));
+    level.insert("InhabitedTime", nbt::NbtValue::Long(inhabited_time));
+    level.insert(
+        "Blocks",
+        nbt::NbtValue::ByteArray(combine_block_sections(&lower_blocks, &upper_blocks)),
+    );
+    level.insert(
+        "Data",
+        nbt::NbtValue::ByteArray(combine_nibble_sections(&lower_data, &upper_data)),
+    );
+    level.insert(
+        "SkyLight",
+        nbt::NbtValue::ByteArray(combine_nibble_sections(&lower_sky, &upper_sky)),
+    );
+    level.insert(
+        "BlockLight",
+        nbt::NbtValue::ByteArray(combine_nibble_sections(
+            &lower_block_light,
+            &upper_block_light,
+        )),
+    );
+    level.insert("HeightMap", nbt::NbtValue::ByteArray(height_map));
+    level.insert(
+        "TerrainPopulatedFlags",
+        nbt::NbtValue::Short(terrain_populated_flags),
+    );
+    level.insert("Biomes", nbt::NbtValue::ByteArray(biomes));
+    let entities = dynamic_root
+        .list("Entities")
+        .map(|l| nbt::NbtValue::List(l.to_vec()))
+        .unwrap_or_else(|| nbt::NbtValue::List(Vec::new()));
+    level.insert("Entities", entities);
+    let tile_entities = dynamic_root
+        .list("TileEntities")
+        .map(|l| nbt::NbtValue::List(l.to_vec()))
+        .unwrap_or_else(|| nbt::NbtValue::List(Vec::new()));
+    level.insert("TileEntities", tile_entities);
+    if let Some(tile_ticks) = dynamic_root.get("TileTicks") {
+        level.insert("TileTicks", tile_ticks.clone());
+    }
+
+    let mut root = nbt::NbtCompound::new("");
+    root.insert("Level", nbt::NbtValue::Compound(level));
+    Ok(root)
+}
+
+pub fn try_get_compressed_chunk_nbt_offset(data: &[u8]) -> Option<usize> {
+    if !is_compressed_chunk_storage(data) {
+        return None;
+    }
+
+    let mut offset = 0;
+    let version = read_be_i16(data, offset);
+    offset = 2;
+    if version != SAVE_FILE_VERSION_COMPRESSED_CHUNK_STORAGE
+        && version != SAVE_FILE_VERSION_CHUNK_INHABITED_TIME
+    {
+        return None;
+    }
+
+    offset += 8;
+    if version >= SAVE_FILE_VERSION_CHUNK_INHABITED_TIME {
+        offset += 8;
+    }
+
+    let r1 = skip_compressed_tile_storage(data, &mut offset);
+    if r1.is_err() { return None; }
+    let r2 = skip_compressed_tile_storage(data, &mut offset);
+    if r2.is_err() { return None; }
+    let r3 = skip_sparse_nibble_storage(data, &mut offset);
+    if r3.is_err() { return None; }
+    let r4 = skip_sparse_nibble_storage(data, &mut offset);
+    if r4.is_err() { return None; }
+    let r5 = skip_sparse_nibble_storage(data, &mut offset);
+    if r5.is_err() { return None; }
+    let r6 = skip_sparse_nibble_storage(data, &mut offset);
+    if r6.is_err() { return None; }
+    let r7 = skip_sparse_nibble_storage(data, &mut offset);
+    if r7.is_err() { return None; }
+    let r8 = skip_sparse_nibble_storage(data, &mut offset);
+    if r8.is_err() { return None; }
+    offset += 256;
+    offset += 2;
+    offset += 256;
+    if offset > data.len() {
+        return None;
+    }
+
+    Some(offset)
+}
diff --git a/src-tauri/src/commands/java2lce/region.rs b/src-tauri/src/commands/java2lce/region.rs
new file mode 100644
index 0000000..6ac5b2c
--- /dev/null
+++ b/src-tauri/src/commands/java2lce/region.rs
@@ -0,0 +1,803 @@
+use std::collections::HashMap;
+use std::fs;
+use std::io::{Read, Write};
+use std::path::Path;
+use flate2::read::ZlibDecoder;
+use flate2::write::ZlibEncoder;
+use flate2::Compression;
+use super::nbt::{self, NbtCompound, NbtValue};
+const SECTOR_BYTES: usize = 4096;
+pub struct JavaWorldReader {
+    world_path: String,
+    region_readers: HashMap<String, JavaRegionReader>,
+}
+
+pub struct JavaRegionReader {
+    pub data: Vec<u8>,
+    pub offsets: [u32; 1024],
+}
+
+impl JavaWorldReader {
+    pub fn new(world_path: &str) -> Self {
+        Self {
+            world_path: world_path.to_string(),
+            region_readers: HashMap::new(),
+        }
+    }
+
+    pub fn read_level_dat(&self) -> Result<NbtCompound, String> {
+        let path = Path::new(&self.world_path).join("level.dat");
+        let data = fs::read(&path).map_err(|e| format!("Failed to read level.dat: {}", e))?;
+        nbt::read_gzip_nbt(&data)
+    }
+
+    pub fn get_region_dir(&self, dimension: &str) -> String {
+        if dimension.is_empty() {
+            Path::new(&self.world_path)
+                .join("region")
+                .to_string_lossy()
+                .to_string()
+        } else {
+            Path::new(&self.world_path)
+                .join(dimension)
+                .join("region")
+                .to_string_lossy()
+                .to_string()
+        }
+    }
+
+    pub fn get_region_files(&self, dimension: &str) -> Vec<(i32, i32, String)> {
+        let mut result = Vec::new();
+        let dir = self.get_region_dir(dimension);
+        let dir_path = Path::new(&dir);
+        if !dir_path.is_dir() {
+            return result;
+        }
+
+        if let Ok(entries) = fs::read_dir(dir_path) {
+            for entry in entries.flatten() {
+                let name = entry.file_name().to_string_lossy().to_string();
+                let lower = name.to_lowercase();
+                if lower.ends_with(".mcr") || lower.ends_with(".mca") {
+                    let parts: Vec<&str> = name.split('.').collect();
+                    if parts.len() == 4 && parts[0] == "r" {
+                        if let (Ok(rx), Ok(rz)) =(parts[1].parse::<i32>(), parts[2].parse::<i32>())
+                        {
+                            result.push((rx, rz, entry.path().to_string_lossy().to_string()));
+                        }
+                    }
+                }
+            }
+        }
+
+        result
+    }
+
+    pub fn is_anvil_world(&self) -> bool {
+        let region_dir = self.get_region_dir("");
+        let dir_path = Path::new(&region_dir);
+        if !dir_path.is_dir() {
+            return false;
+        }
+        if let Ok(entries) = fs::read_dir(dir_path) {
+            for entry in entries.flatten() {
+                let name = entry.file_name().to_string_lossy().to_string();
+                if name.to_lowercase().ends_with(".mca") {
+                    return true;
+                }
+            }
+        }
+        false
+    }
+
+    fn get_or_create_reader(&mut self, region_path: &str) -> Result<&JavaRegionReader, String> {
+        if !self.region_readers.contains_key(region_path) {
+            let reader = JavaRegionReader::open(region_path)?;
+            self.region_readers.insert(region_path.to_string(), reader);
+        }
+        Ok(self.region_readers.get(region_path).unwrap())
+    }
+
+    pub fn has_chunk(&mut self, region_path: &str, local_x: i32, local_z: i32) -> bool {
+        let reader = match self.get_or_create_reader(region_path) {
+            Ok(r) => r,
+            Err(_) => return false,
+        };
+        let index = (local_x & 31) + (local_z & 31) * 32;
+        reader.offsets[index as usize] != 0
+    }
+
+    pub fn read_chunk_nbt(
+        &mut self,
+        region_path: &str,
+        local_x: i32,
+        local_z: i32,
+    ) -> Result<Option<NbtCompound>, String> {
+        let reader = self.get_or_create_reader(region_path)?;
+        let index = (local_x & 31) + (local_z & 31) * 32;
+        let offset_entry = reader.offsets[index as usize];
+        if offset_entry == 0 {
+            return Ok(None);
+        }
+
+        let sector_offset = (offset_entry >> 8) as usize;
+        let chunk_pos = sector_offset * SECTOR_BYTES;
+        let data_len = reader.data.len();
+        if chunk_pos + 5 > data_len {
+            return Ok(None);
+        }
+
+        let length = u32::from_be_bytes([
+            reader.data[chunk_pos],
+            reader.data[chunk_pos + 1],
+            reader.data[chunk_pos + 2],
+            reader.data[chunk_pos + 3],
+        ]) as usize;
+        let compression_type = reader.data[chunk_pos + 4];
+        if length <= 1 {
+            return Ok(None);
+        }
+
+        let compressed_length = length - 1;
+        if chunk_pos + 5 + compressed_length > data_len {
+            return Ok(None);
+        }
+
+        let compressed_data = &reader.data[chunk_pos + 5..chunk_pos + 5 + compressed_length];
+        let decompressed = match compression_type {
+            1 => {
+                let mut decoder = flate2::read::GzDecoder::new(compressed_data);
+                let mut buf = Vec::new();
+                decoder.read_to_end(&mut buf).map_err(|e| format!("gzip decompress failed: {}", e))?;
+                buf
+            }
+            2 => {
+                let mut decoder = ZlibDecoder::new(compressed_data);
+                let mut buf = Vec::new();
+                decoder
+                    .read_to_end(&mut buf)
+                    .map_err(|e| format!("zlib decompress failed: {}", e))?;
+                buf
+            }
+            _ => return Ok(None),
+        };
+
+        if decompressed.is_empty() {
+            return Ok(None);
+        }
+
+        let compound = nbt::read_nbt(&decompressed)?;
+        Ok(Some(compound))
+    }
+}
+
+impl JavaRegionReader {
+    fn open(path: &str) -> Result<Self, String> {
+        let data = fs::read(path).map_err(|e| format!("Failed to read region file: {}", e))?;
+        let mut offsets = [0u32; 1024];
+        for i in 0..1024 {
+            let off = i * 4;
+            if off + 4 > data.len() {
+                break;
+            }
+            offsets[i] = u32::from_be_bytes([data[off], data[off + 1], data[off + 2], data[off + 3]]);
+        }
+
+        Ok(Self { data, offsets })
+    }
+
+    pub fn open_from_bytes(data: &[u8]) -> Self {
+        let data = data.to_vec();
+        let mut offsets = [0u32; 1024];
+        for i in 0..1024 {
+            let off = i * 4;
+            if off + 4 > data.len() {
+                break;
+            }
+            offsets[i] = u32::from_be_bytes([data[off], data[off + 1], data[off + 2], data[off + 3]]);
+        }
+
+        Self { data, offsets }
+    }
+
+    pub fn read_chunk(
+        &mut self,
+        local_x: i32,
+        local_z: i32,
+    ) -> Result<Option<Vec<u8>>, String> {
+        let index = (local_x & 31) + (local_z & 31) * 32;
+        let offset_entry = self.offsets[index as usize];
+        if offset_entry == 0 {
+            return Ok(None);
+        }
+
+        let sector_offset = (offset_entry >> 8) as usize;
+        let chunk_pos = sector_offset * SECTOR_BYTES;
+        let data_len = self.data.len();
+        if chunk_pos + 5 > data_len {
+            return Ok(None);
+        }
+
+        let length = u32::from_be_bytes([
+            self.data[chunk_pos],
+            self.data[chunk_pos + 1],
+            self.data[chunk_pos + 2],
+            self.data[chunk_pos + 3],
+        ]) as usize;
+        let compression_type = self.data[chunk_pos + 4];
+        if length <= 1 {
+            return Ok(None);
+        }
+
+        let compressed_length = length - 1;
+        if chunk_pos + 5 + compressed_length > data_len {
+            return Ok(None);
+        }
+
+        let compressed_data = &self.data[chunk_pos + 5..chunk_pos + 5 + compressed_length];
+        let decompressed = match compression_type {
+            1 => {
+                let mut decoder = flate2::read::GzDecoder::new(compressed_data);
+                let mut buf = Vec::new();
+                decoder
+                    .read_to_end(&mut buf)
+                    .map_err(|e| format!("gzip decompress failed: {}", e))?;
+                buf
+            }
+            2 => {
+                let mut decoder = ZlibDecoder::new(compressed_data);
+                let mut buf = Vec::new();
+                decoder
+                    .read_to_end(&mut buf)
+                    .map_err(|e| format!("zlib decompress failed: {}", e))?;
+                buf
+            }
+            _ => return Ok(None),
+        };
+
+        if decompressed.is_empty() {
+            return Ok(None);
+        }
+
+        Ok(Some(decompressed))
+    }
+}
+
+pub struct JavaRegionFileWriter {
+    path: String,
+    buffer: Vec<u8>,
+    offsets: [i32; 1024],
+    timestamps: [i32; 1024],
+    next_sector: usize,
+}
+
+impl JavaRegionFileWriter {
+    pub fn new(path: &str) -> Self {
+        let buffer = vec![0u8; SECTOR_BYTES * 2];
+        let offsets = [0i32; 1024];
+        let timestamps = [0i32; 1024];
+        Self {
+            path: path.to_string(),
+            buffer,
+            offsets,
+            timestamps,
+            next_sector: 2,
+        }
+    }
+
+    pub fn load_from_file(path: &str) -> Self {
+        if let Ok(data) = fs::read(path) {
+            let buffer = data.clone();
+            let mut offsets = [0i32; 1024];
+            let mut timestamps = [0i32; 1024];
+            for i in 0..1024 {
+                let pos = i * 4;
+                if pos + 4 <= data.len() {
+                    offsets[i] = i32::from_be_bytes([data[pos], data[pos + 1], data[pos + 2], data[pos + 3]]);
+                }
+            }
+
+            for i in 0..1024 {
+                let pos = SECTOR_BYTES + i * 4;
+                if pos + 4 <= data.len() {
+                    timestamps[i] = i32::from_be_bytes([data[pos], data[pos + 1], data[pos + 2], data[pos + 3]]);
+                }
+            }
+
+            let mut max_sector = 2;
+            for &off in &offsets {
+                if off != 0 {
+                    let sector = (off >> 8) as usize;
+                    let count = (off & 0xFF) as usize;
+                    let end = sector + count;
+                    if end > max_sector {
+                        max_sector = end;
+                    }
+                }
+            }
+
+            Self {
+                path: path.to_string(),
+                buffer,
+                offsets,
+                timestamps,
+                next_sector: max_sector,
+            }
+        } else {
+            Self::new(path)
+        }
+    }
+
+    pub fn write_chunk(&mut self, local_x: i32, local_z: i32, uncompressed_nbt: &[u8]) {
+        if local_x < 0 || local_x > 31 || local_z < 0 || local_z > 31 {
+            return;
+        }
+
+        let compressed = compress_zlib(uncompressed_nbt);
+        let payload_length = 1 + compressed.len();
+        let total_length = 4 + payload_length;
+        let sectors_needed = (total_length + SECTOR_BYTES - 1) / SECTOR_BYTES;
+        if sectors_needed >= 256 {
+            return;
+        }
+
+        let sector_start = self.next_sector;
+        self.next_sector += sectors_needed;
+        while self.buffer.len() < (sector_start + sectors_needed) * SECTOR_BYTES {
+            self.buffer.extend(std::iter::repeat(0u8).take(SECTOR_BYTES));
+        }
+
+        let write_pos = sector_start * SECTOR_BYTES;
+        self.buffer[write_pos..write_pos + 4]
+            .copy_from_slice(&(payload_length as u32).to_be_bytes());
+        self.buffer[write_pos + 4] = 2;
+        self.buffer[write_pos + 5..write_pos + 5 + compressed.len()]
+            .copy_from_slice(&compressed);
+
+        let padding = sectors_needed * SECTOR_BYTES - total_length;
+        if padding > 0 {
+            for i in 0..padding {
+                self.buffer[write_pos + total_length + i] = 0;
+            }
+        }
+
+        let offset_index = (local_x & 31) + (local_z & 31) * 32;
+        self.offsets[offset_index as usize] = ((sector_start as i32) << 8) | (sectors_needed as i32);
+        let now = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_secs() as i32;
+        self.timestamps[offset_index as usize] = now;
+    }
+
+    pub fn save(&mut self) -> Result<(), String> {
+        while self.buffer.len() < self.next_sector * SECTOR_BYTES {
+            self.buffer.extend(std::iter::repeat(0u8).take(SECTOR_BYTES));
+        }
+
+        for i in 0..1024 {
+            let pos = i * 4;
+            self.buffer[pos..pos + 4].copy_from_slice(&(self.offsets[i] as u32).to_be_bytes());
+        }
+
+        for i in 0..1024 {
+            let pos = SECTOR_BYTES + i * 4;
+            self.buffer[pos..pos + 4]
+                .copy_from_slice(&(self.timestamps[i] as u32).to_be_bytes());
+        }
+
+        let total = self.next_sector * SECTOR_BYTES;
+        let data = &self.buffer[..total];
+        if let Some(parent) = Path::new(&self.path).parent() {
+            fs::create_dir_all(parent)
+                .map_err(|e| format!("Failed to create region directory: {}", e))?;
+        }
+
+        fs::write(&self.path, data)
+            .map_err(|e| format!("Failed to write region file: {}", e))?;
+        Ok(())
+    }
+}
+
+pub struct LceRegionFile {
+    filename: String,
+    data: Vec<u8>,
+    offsets: [i32; 1024],
+    timestamps: [i32; 1024],
+    region_x: i32,
+    region_z: i32,
+    sector_count: usize,
+}
+
+impl LceRegionFile {
+    pub fn new(filename: &str) -> Self {
+        let (region_x, region_z) = parse_region_coordinates(filename);
+        let data = vec![0u8; SECTOR_BYTES * 2];
+        Self {
+            filename: filename.to_string(),
+            data,
+            offsets: [0i32; 1024],
+            timestamps: [0i32; 1024],
+            region_x,
+            region_z,
+            sector_count: 2,
+        }
+    }
+
+    pub fn write_chunk(&mut self, x: i32, z: i32, mut uncompressed_data: Vec<u8>) {
+        if x < 0 || x >= 32 || z < 0 || z >= 32 {
+            return;
+        }
+        if uncompressed_data.is_empty() {
+            return;
+        }
+
+        uncompressed_data = force_chunk_coordinates(
+            &uncompressed_data,
+            self.region_x * 32 + x,
+            self.region_z * 32 + z,
+        );
+        if uncompressed_data.is_empty() {
+            return;
+        }
+
+        let compressed = compress_zlib_only(&uncompressed_data);
+        let total_size = 8 + compressed.len();
+        let sectors_needed = (total_size + SECTOR_BYTES - 1) / SECTOR_BYTES;
+        if sectors_needed >= 256 {
+            return;
+        }
+
+        let sector_number = self.sector_count;
+        self.sector_count += sectors_needed;
+        while self.data.len() < (sector_number + sectors_needed) * SECTOR_BYTES {
+            self.data.extend(std::iter::repeat(0u8).take(SECTOR_BYTES));
+        }
+
+        let write_pos = sector_number * SECTOR_BYTES;
+        let stored_length = compressed.len() as u32;
+        self.data[write_pos..write_pos + 4]
+            .copy_from_slice(&stored_length.to_le_bytes());
+        self.data[write_pos + 4..write_pos + 8]
+            .copy_from_slice(&(uncompressed_data.len() as u32).to_le_bytes());
+        self.data[write_pos + 8..write_pos + 8 + compressed.len()]
+            .copy_from_slice(&compressed);
+
+        let padding = sectors_needed * SECTOR_BYTES - total_size;
+        if padding > 0 {
+            for i in 0..padding {
+                self.data[write_pos + total_size + i] = 0;
+            }
+        }
+
+        let offset_index = (x + z * 32) as usize;
+        self.offsets[offset_index] = ((sector_number as i32) << 8) | (sectors_needed as i32);
+        let now = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_secs() as i32;
+        self.timestamps[offset_index] = now;
+    }
+
+    pub fn write_to_container(&mut self, container: &mut SaveDataContainer) {
+        let _sorted_entries: Vec<(usize, i32, i32)> = (0..1024)
+            .map(|i| (i, self.offsets[i], self.timestamps[i]))
+            .filter(|(_, off, _)| *off != 0)
+            .collect();
+
+        for i in 0..1024 {
+            let pos = i * 4;
+            self.data[pos..pos + 4].copy_from_slice(&(self.offsets[i] as u32).to_le_bytes());
+        }
+
+        for i in 0..1024 {
+            let pos = SECTOR_BYTES + i * 4;
+            self.data[pos..pos + 4]
+                .copy_from_slice(&(self.timestamps[i] as u32).to_le_bytes());
+        }
+
+        let total = self.sector_count * SECTOR_BYTES;
+        let region_bytes = self.data[..total].to_vec();
+        let entry = container.create_file(&self.filename);
+        container.write_to_file(entry, &region_bytes);
+    }
+}
+
+fn parse_region_coordinates(filename: &str) -> (i32, i32) {
+    let name = Path::new(filename)
+        .file_stem()
+        .unwrap_or_default()
+        .to_string_lossy()
+        .to_string();
+    let parts: Vec<&str> = name.split('.').collect();
+    if parts.len() < 3 {
+        return (0, 0);
+    }
+    let rx = parts[parts.len() - 2].parse().unwrap_or(0);
+    let rz = parts[parts.len() - 1].parse().unwrap_or(0);
+    (rx, rz)
+}
+
+pub fn force_chunk_coordinates(data: &[u8], expected_x: i32, expected_z: i32) -> Vec<u8> {
+    if data.is_empty() {
+        return Vec::new();
+    }
+
+    if let Ok(mut compound) = nbt::read_nbt(data) {
+        let has_level = compound.get("Level").is_some();
+        if has_level {
+            if let Some(nbt::NbtValue::Compound(ref mut c)) = compound.get_mut("Level") {
+                c.insert("xPos", NbtValue::Int(expected_x));
+                c.insert("zPos", NbtValue::Int(expected_z));
+            }
+        } else {
+            compound.insert("xPos", NbtValue::Int(expected_x));
+            compound.insert("zPos", NbtValue::Int(expected_z));
+        }
+
+        let mut root = NbtCompound::new("");
+        root.insert("Level", NbtValue::Compound(compound));
+        nbt::write_nbt(&root)
+    } else if data.len() >= 10 {
+        let version = i16::from_be_bytes([data[0], data[1]]);
+        if version == 8 || version == 9 {
+            let mut patched = data.to_vec();
+            patched[2..6].copy_from_slice(&expected_x.to_be_bytes());
+            patched[6..10].copy_from_slice(&expected_z.to_be_bytes());
+            return patched;
+        }
+        Vec::new()
+    } else {
+        Vec::new()
+    }
+}
+
+pub struct SaveDataContainer {
+    original_save_version: i16,
+    current_save_version: i16,
+    entries: Vec<SaveFileEntry>,
+    blob: Vec<u8>,
+    data_end: usize,
+}
+
+pub struct SaveFileEntry {
+    pub name: String,
+    pub length: u32,
+    pub start_offset: u32,
+    pub last_mod: i64,
+    pub current_pointer: u32,
+}
+
+impl SaveDataContainer {
+    pub const FILE_ENTRY_SIZE: usize = 144;
+    pub fn new(original_save_version: i16, current_save_version: i16) -> Self {
+        Self {
+            original_save_version,
+            current_save_version,
+            entries: Vec::new(),
+            blob: vec![0u8; 2 * 1024 * 1024],
+            data_end: 12,
+        }
+    }
+
+    pub fn create_file(&mut self, name: &str) -> usize {
+        if let Some(idx) = self.entries.iter().position(|e| e.name == name) {
+            return idx;
+        }
+        let entry = SaveFileEntry {
+            name: name.to_string(),
+            length: 0,
+            start_offset: self.data_end as u32,
+            last_mod: 0,
+            current_pointer: self.data_end as u32,
+        };
+        self.entries.push(entry);
+        self.entries.len() - 1
+    }
+
+    pub fn write_to_file(&mut self, index: usize, data: &[u8]) {
+        if data.is_empty() {
+            return;
+        }
+
+        let needs_reinit = self.entries[index].length == 0;
+        if needs_reinit {
+            self.entries[index].start_offset = self.data_end as u32;
+            self.entries[index].current_pointer = self.data_end as u32;
+        }
+
+        let write_pos = self.entries[index].current_pointer as usize;
+        let end_pos = write_pos + data.len();
+        self.ensure_capacity(end_pos);
+        self.blob[write_pos..write_pos + data.len()].copy_from_slice(data);
+        self.entries[index].current_pointer += data.len() as u32;
+        let written = self.entries[index].current_pointer - self.entries[index].start_offset;
+        if written > self.entries[index].length {
+            self.entries[index].length = written;
+        }
+
+        let entry_end = (self.entries[index].start_offset + self.entries[index].length) as usize;
+        if entry_end > self.data_end {
+            self.data_end = entry_end;
+        }
+
+        let now = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_millis() as i64;
+        self.entries[index].last_mod = now;
+    }
+
+    pub fn save(&mut self, output_path: &str) -> Result<(), String> {
+        self.write_header();
+        let total_size = self.data_end + self.entries.len() * Self::FILE_ENTRY_SIZE;
+        self.ensure_capacity(total_size);
+        self.write_footer();
+        let raw_blob = self.blob[..total_size].to_vec();
+        let mut encoder = ZlibEncoder::new(Vec::new(), Compression::best());
+        encoder
+            .write_all(&raw_blob)
+            .map_err(|e| format!("zlib compress failed: {}", e))?;
+        let compressed_data = encoder
+            .finish()
+            .map_err(|e| format!("zlib finish failed: {}", e))?;
+
+        if let Some(parent) = Path::new(output_path).parent() {
+            fs::create_dir_all(parent)
+                .map_err(|e| format!("Failed to create output directory: {}", e))?;
+        }
+
+        let mut file = fs::File::create(output_path)
+            .map_err(|e| format!("Failed to create output file: {}", e))?;
+        file.write_all(&(0u32).to_le_bytes())
+            .map_err(|e| format!("write failed: {}", e))?;
+        file.write_all(&(total_size as u32).to_le_bytes())
+            .map_err(|e| format!("write failed: {}", e))?;
+        file.write_all(&compressed_data)
+            .map_err(|e| format!("write failed: {}", e))?;
+        Ok(())
+    }
+
+    fn write_header(&mut self) {
+        self.blob[0..4]
+            .copy_from_slice(&(self.data_end as u32).to_le_bytes());
+        self.blob[4..8]
+            .copy_from_slice(&(self.entries.len() as u32).to_le_bytes());
+        self.blob[8..10]
+            .copy_from_slice(&self.original_save_version.to_le_bytes());
+        self.blob[10..12]
+            .copy_from_slice(&self.current_save_version.to_le_bytes());
+    }
+
+    fn write_footer(&mut self) {
+        let mut sorted: Vec<usize> = (0..self.entries.len()).collect();
+        sorted.sort_by_key(|&i| self.entries[i].start_offset);
+        let mut pos = self.data_end;
+        for &i in &sorted {
+            let entry = &self.entries[i];
+            let mut name_bytes = vec![0u8; 128];
+            let encoded: Vec<u8> = entry
+                .name
+                .encode_utf16()
+                .flat_map(|c| c.to_le_bytes())
+                .collect();
+            let copy_len = encoded.len().min(126);
+            name_bytes[..copy_len].copy_from_slice(&encoded[..copy_len]);
+            self.blob[pos..pos + 128].copy_from_slice(&name_bytes);
+            pos += 128;
+            self.blob[pos..pos + 4].copy_from_slice(&entry.length.to_le_bytes());
+            pos += 4;
+            self.blob[pos..pos + 4].copy_from_slice(&entry.start_offset.to_le_bytes());
+            pos += 4;
+            self.blob[pos..pos + 8].copy_from_slice(&entry.last_mod.to_le_bytes());
+            pos += 8;
+        }
+    }
+
+    fn ensure_capacity(&mut self, required: usize) {
+        if required <= self.blob.len() {
+            return;
+        }
+        let mut new_size = self.blob.len();
+        while new_size < required {
+            new_size *= 2;
+        }
+        self.blob.resize(new_size, 0);
+    }
+}
+
+pub fn compress_zlib(data: &[u8]) -> Vec<u8> {
+    let mut encoder = ZlibEncoder::new(Vec::new(), Compression::best());
+    encoder.write_all(data).unwrap();
+    encoder.finish().unwrap()
+}
+
+pub fn compress_zlib_only(data: &[u8]) -> Vec<u8> {
+    compress_zlib(data)
+}
+
+pub fn decompress_zlib(data: &[u8]) -> Result<Vec<u8>, String> {
+    let mut decoder = ZlibDecoder::new(data);
+    let mut buf = Vec::new();
+    decoder.read_to_end(&mut buf).map_err(|e| format!("zlib decompress failed: {}", e))?;
+    Ok(buf)
+}
+
+pub fn decompress_rle_zlib(data: &[u8], decompressed_size: usize) -> Result<Vec<u8>, String> {
+    let rle_data = decompress_zlib(data)?;
+    Ok(rle_decode(&rle_data, decompressed_size))
+}
+
+pub fn rle_encode(data: &[u8]) -> Vec<u8> {
+    let mut out = Vec::new();
+    let mut i = 0;
+    while i < data.len() {
+        let current = data[i];
+        i += 1;
+        let mut count = 1usize;
+        while i < data.len() && data[i] == current && count < 256 {
+            i += 1;
+            count += 1;
+        }
+
+        if count <= 3 {
+            if current == 0xFF {
+                out.push(0xFF);
+                out.push((count - 1) as u8);
+            } else {
+                for _ in 0..count {
+                    out.push(current);
+                }
+            }
+        } else {
+            out.push(0xFF);
+            out.push((count - 1) as u8);
+            out.push(current);
+        }
+    }
+    out
+}
+
+pub fn rle_decode(data: &[u8], expected_size: usize) -> Vec<u8> {
+    let mut output = vec![0u8; expected_size];
+    let mut in_pos = 0;
+    let mut out_pos = 0;
+    while in_pos < data.len() && out_pos < expected_size {
+        let current = data[in_pos];
+        in_pos += 1;
+        if current == 0xFF {
+            if in_pos >= data.len() {
+                break;
+            }
+            let count = data[in_pos] as usize;
+            in_pos += 1;
+            if count < 3 {
+                let run = count + 1;
+                for _ in 0..run {
+                    if out_pos < expected_size {
+                        output[out_pos] = 0xFF;
+                        out_pos += 1;
+                    }
+                }
+            } else {
+                let run = count + 1;
+                if in_pos >= data.len() {
+                    break;
+                }
+                let value = data[in_pos];
+                in_pos += 1;
+                for _ in 0..run {
+                    if out_pos < expected_size {
+                        output[out_pos] = value;
+                        out_pos += 1;
+                    }
+                }
+            }
+        } else {
+            output[out_pos] = current;
+            out_pos += 1;
+        }
+    }
+
+    output
+}
diff --git a/src-tauri/src/commands/mod.rs b/src-tauri/src/commands/mod.rs
index 38b63f4..e6ca211 100644
--- a/src-tauri/src/commands/mod.rs
+++ b/src-tauri/src/commands/mod.rs
@@ -4,6 +4,7 @@ pub mod dlc;
 pub mod download;
 pub mod file_dialogs;
 pub mod game;
+pub mod java2lce;
 pub mod macos_setup;
 pub mod plugins;
 pub mod proxy_cmd;
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index 25151d8..cfc2f6a 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -109,6 +109,8 @@ pub fn run() {
             game::restore_instance,
             commands::console2lce::import_world,
             commands::console2lce::import_lce_save,
+            commands::java2lce::java_to_lce,
+            commands::java2lce::lce_to_java,
             stun::stun_discover,
             relay::start_relay_proxy,
             relay::start_host_relay,
diff --git a/src-tauri/src/networking/relay.rs b/src-tauri/src/networking/relay.rs
index f4773c5..1046cf0 100644
--- a/src-tauri/src/networking/relay.rs
+++ b/src-tauri/src/networking/relay.rs
@@ -1,8 +1,6 @@
 use tauri::State;
-use tauri::webview::cookie::time::Duration;
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 use tokio::net::{TcpListener, TcpStream};
-use tokio::time::sleep;
 use tokio_util::sync::CancellationToken;
 use crate::state::ProxyGuard;
 const PROXY_ADDR: &str = "proxy.mclegacyedition.xyz:2052"; //neo: yeah bro im hardcoding it
diff --git a/src/components/modals/ImportWorldModal.tsx b/src/components/modals/ImportWorldModal.tsx
index 5cf5bb7..b6d2435 100644
--- a/src/components/modals/ImportWorldModal.tsx
+++ b/src/components/modals/ImportWorldModal.tsx
@@ -120,6 +120,70 @@ export default function ImportWorldModal({
     }
   };
 
+  const handleImportJava = async () => {
+    if (!targetInstanceId) return;
+    playPressSound();
+    setIsImporting(true);
+    setError("");
+    setStatus("Selecting source...");
+    try {
+      setStatus("Selecting Java world folder...");
+      const picked = await TauriService.pickFolder();
+      if (!picked) {
+        setIsImporting(false);
+        return;
+      }
+      const worldName = deriveWorldName(picked);
+      setStatus("Converting Java world to LCE...");
+      const instancePath = await TauriService.getInstancePath(targetInstanceId);
+      const saveDir = `${instancePath}/Windows64/GameHDD/${worldName}`;
+      await TauriService.javaToLce(picked, `${saveDir}/saveData.ms`);
+      setStatus(`Java world converted into "${targetInstanceName}"!`);
+      setTimeout(() => {
+        onClose();
+      }, 2000);
+    } catch (e: unknown) {
+      setError(e instanceof Error ? e.message : String(e));
+      setStatus("");
+      setIsImporting(false);
+    }
+  };
+
+  const handleExportJava = async () => {
+    if (!targetInstanceId) return;
+    playPressSound();
+    setIsImporting(true);
+    setError("");
+    setStatus("Selecting source...");
+    try {
+      setStatus("Selecting saveData.ms file...");
+      const picked = await TauriService.pickFile("Select saveData.ms", [
+        "*.ms",
+        "*",
+      ]);
+      if (!picked) {
+        setIsImporting(false);
+        return;
+      }
+      setStatus("Selecting output folder for Java world...");
+      const outputFolder = await TauriService.pickFolder();
+      if (!outputFolder) {
+        setIsImporting(false);
+        return;
+      }
+      setStatus("Converting LCE save to Java world...");
+      await TauriService.lceToJava(picked, outputFolder);
+      setStatus(`Java world exported to "${outputFolder}"!`);
+      setTimeout(() => {
+        onClose();
+      }, 2000);
+    } catch (e: unknown) {
+      setError(e instanceof Error ? e.message : String(e));
+      setStatus("");
+      setIsImporting(false);
+    }
+  };
+
   const handleKey = (e: KeyboardEvent) => {
     if (e.key === "Escape") {
       playBackSound();
@@ -204,6 +268,34 @@ export default function ImportWorldModal({
               </button>
             </div>
 
+            <p className="text-gray-400 text-xs mc-text-shadow mb-2 text-center">
+              Java Edition world conversion:
+            </p>
+            <div className="flex gap-3 mb-2">
+              <button
+                onClick={handleImportJava}
+                className="w-40 h-9 flex items-center justify-center text-sm text-white mc-text-shadow hover:text-[#FFFF55]"
+                style={{
+                  backgroundImage: "url('/images/Button_Background.png')",
+                  backgroundSize: "100% 100%",
+                  imageRendering: "pixelated",
+                }}
+              >
+                Java → LCE
+              </button>
+              <button
+                onClick={handleExportJava}
+                className="w-40 h-9 flex items-center justify-center text-sm text-white mc-text-shadow hover:text-[#FFFF55]"
+                style={{
+                  backgroundImage: "url('/images/Button_Background.png')",
+                  backgroundSize: "100% 100%",
+                  imageRendering: "pixelated",
+                }}
+              >
+                LCE → Java
+              </button>
+            </div>
+
             {error && (
               <div className="text-red-500 text-center mc-text-shadow uppercase text-xs tracking-widest mb-3">
                 {error}
diff --git a/src/services/TauriService.ts b/src/services/TauriService.ts
index bc01e99..4ada2a8 100644
--- a/src/services/TauriService.ts
+++ b/src/services/TauriService.ts
@@ -427,4 +427,18 @@ export class TauriService {
   ): Promise<string> {
     return invoke("import_lce_save", { inputPath, outputDir });
   }
+
+  static async javaToLce(
+    javaWorldPath: string,
+    outputMsPath: string,
+  ): Promise<string> {
+    return invoke("java_to_lce", { javaWorldPath, outputMsPath });
+  }
+
+  static async lceToJava(
+    inputMsPath: string,
+    javaWorldOutput: string,
+  ): Promise<string> {
+    return invoke("lce_to_java", { inputMsPath, javaWorldOutput });
+  }
 }