Switch from add-then-XOR pattern to proper sequential multiply-add
avalanche. Each coordinate feeds into the next multiply, preventing
correlation between adjacent tiles when rare drops are introduced.
- SmallVec<[DropEntry; 2]> replaces Vec in DropTable: zero heap allocation for
all current tiles (0 or 1 entries), spills to heap only at 3+
- DropEntry fields packed to u8 (chance_pct, min_count, max_count): ~12 bytes ->
4 bytes; derives Copy so no extra clones
- Replaced SystemTime pseudo-RNG with dig_rng(pos): PCG-style hash of world SEED
+ tile position. Deterministic per world, same dig = same roll every time
- TOML-driven drop tables: assets/drop_tables.toml (grass=5%/1-2, rock=10%/1,
dirt/air=none). TOML parsed at startup into DropTableRegistry resource
- OnceLock global map for async terrain generation tasks to access drop tables
without Bevy resource borrowing
- terrain.rs: DropTableRegistry::global_get("tile") replaces hardcoded drop_table_for
- Add generic digging + drop tables to implemented list
- Rabbit digging: now using Digger component, not debug code
- Building and construction: updated to reflect generic system in place
- Architecture: added digging to shared_systems, drop_table to tiles
- New src/entities/item/drop_table.rs: DropEntry (chance, min/max count,
pseudo-RNG roll) + DropTable wrapper. grass=5% coin 1-2, rock=10% coin 1,
dirt/air=none.
- New src/entities/shared_systems/digging.rs: Digger component + dig_system.
Any entity with Digger digs the tile below on its interval. Replaces
rabbit_dig_system/rabbit_fall_debug_system/RabbitDigTimer/RabbitFallDebug.
- New TileMap::dig_floor: remove_floor + insert air. Used by dig_system.
- FloorTileData: added drop_table field. Lost Copy derive (Vec field).
Updated all 6 terrain.rs call sites with per-tile drop tables.
- Pig: removed PigDropTimer + pig_drop_system. Drops were debug placeholder.
TODO added for future loot-on-death/butcher system.
- Rabbit: removed all debug components/systems. Now uses Digger::new(5.0).
- main.rs: removed rabbit_dig_system/rabbit_fall_debug_system/pig_drop_system,
added shared_systems::digging::dig_system.
- TileMap::insert_floor now syncs ChunkData bits (set_floor_tile) so is_standable
returns correct values for tiles inserted via insert_floor. Previously the
HashMap was updated but ChunkData remained stale, causing is_standable to
return false for valid tiles.
- rabbit_dig_system inserts air tile at the dug position after remove_floor.
Without this, the HashMap entry is absent and ChunkData bits stay 0 (both
false), making is_standable return false at that position. The entity then
falls through multiple levels. Air's can_stand_in=true means the space is
passable — the entity falls through it and lands on solid ground below.
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