Module reference for the `kiln-core` crate — the engine: all core game types
(`Board`, `Glyph`, `Archetype`, `GameState`, …) plus `.toml` map-file
load/save. No rendering or UI; every front-end depends on it. See the
repository-root `CLAUDE.md` for project-wide guidance, code style, the world
file format, and key design decisions.
The core types that were formerly monolithic in `game.rs` are now split into focused modules. `game.rs` contains only `GameState`; the data types live in their own files.
**`kiln-core/src/glyph.rs`** — per-cell visual:
-`Glyph` (`Copy`, `Eq`, `Hash`) — `tile: u32` (tilesheet index), `fg/bg: Rgba8`. `Glyph::player()` is a `const fn` (tile 64 `@`, white on dark blue); all other glyphs come from map files. `Hash` is hand-implemented via packed `u32` representations so it stays in sync with `Eq`.
**`kiln-core/src/cp437.rs`** — tile-index → character mapping (`pub`):
-`CP437: [char; 256]` — full code-page-437 table (graphic glyphs for 0x00–0x1F, box-drawing for 0xB0–0xDF, etc.). `tile_to_char(tile: u32) -> char` indexes it for `tile < 256`; falls back to `char::from_u32` then a blank space. Unit-tested. Lives in core (not a front-end) because it is the *meaning* of a tile index under the default font; used by kiln-tui's renderer (`render.rs`) and kiln-ui's glyph picker alike.
**`kiln-core/src/colors.rs`** — the named color palette (`pub`):
-`NAMED_COLORS: [(&str, Rgba8); 16]` — the 16 EGA/VGA palette colors as `(name, color)` pairs in palette order (`Black`, `Blue`, …, `White`). The **single source of truth**: `script::register_global_constants` builds the Rhai `Black`/`Blue`/… `"#RRGGBB"` constants from it, and kiln-ui's glyph picker builds its named-swatch strips from it, so the two never drift.
**`kiln-core/src/archetype.rs`** — element taxonomy:
-`Archetype` (`Copy`, `PartialEq`, `Hash`) — enum of named element types: `Empty`, `Wall`, `Crate`, `HCrate`, `VCrate`, `Pusher(Direction)`, `Spinner(SpinDirection)`, `Gem`, `ErrorBlock`. Each variant provides `behavior()`, `name()` (used in map files), and `default_glyph()`. `Crate` pushable any direction (CP437 ■, char 254); `HCrate`/`VCrate` pushable east/west (↔, char 29) / north/south (↕, char 18) only. `Pusher(dir)` (`pusher_north|south|east|west`) is a **map-file keyword only**: at load it expands into a scripted object (see [`builtin_scripts`]), never a terrain cell. `Spinner(SpinDirection)` (`SpinDirection::{Clockwise,CounterClockwise}`; keywords `spinner_cw|spinner_ccw`) is the same kind of script-backed keyword: it expands into a `spinner.rhai` object that rotates its 8 neighbours each 0.5 s and animates its glyph (default glyph is the first frame, `/` CW / `\` CCW, gray on black). `Gem` (keyword `gem`) is also a script-backed keyword: solid + non-opaque + pushable + **grab** (the only archetype with `grab: true`), it expands into a `gem.rhai` object (default glyph blue ♦, CP437 tile 4) whose `grab()` hook adds a gem to the player and `die()`s. `ErrorBlock` is a sentinel for unknown archetype names (yellow `?` on red). `TryFrom<&str>` parses by name; unrecognized names return `Err` (the map loader substitutes `ErrorBlock`).
-`archetype_script(arch) -> Option<&'static str>` — the dispatch (one arm per script-backed archetype) returning the embedded Rhai source (`include_str!`); currently `Pusher(_) -> scripts/pusher.rhai`, `Spinner(_) -> scripts/spinner.rhai`, and `Gem -> scripts/gem.rhai` (just `fn grab() { add_gems(1); die(); }`). Such an archetype loads as a plain terrain cell (`layer::resolve_entry`); `Board::expand_builtin_archetypes` (called from `TryFrom<MapFile>` at load and again before a playtest) is the **single** place that turns it into an `ObjectDef` carrying that source in `builtin_script` plus a `BUILTIN_<archetype>` tag. The spinner reads its `BUILTIN_spinner_cw`/`_ccw` tag for spin direction (defaulting clockwise) and stores per-instance animation frame state in the board `Registry`.
-`BUILTIN_TAG_PREFIX` (`"BUILTIN_"`), `builtin_tag(arch) -> String`, `archetype_from_builtin_tag(tag) -> Option<Archetype>` — the tag convention. The script reads its tag for per-instance params (the pusher reads it for its direction, since `Me` isn't visible inside Rhai helper functions); `map_file::save` uses it to collapse the object back into its archetype keyword so maps round-trip. `scripts/pusher.rhai` self-propels via `move(dir)` (which already shoves chains via `step_object`/`push`), pacing itself with `delay` to the old ~0.5 s cadence.
-`Behavior` — plain data struct from `Archetype::behavior()`: `solid: bool`, `opaque: bool`, `pushable: Pushable`, `grab: bool` (walking into a `solid + grab` thing isn't blocked — the player moves onto it and its `grab()` hook fires; only `Gem` sets it).
-`ObjectDef` — a scripted tile: `x`, `y`, `z: usize` (layer index, drives draw order), `glyph: Glyph`, `solid: bool` (default `true`), `opaque: bool` (default `true`), `pushable: bool` (default `false`), `grab: bool` (default `false`; set when a grab archetype like a gem is expanded — walking onto it fires `grab()`), `script_name: Option<String>`, `builtin_script: Option<&'static str>` (embedded source set when a script-backed archetype like a pusher is expanded at load; takes precedence over `script_name`; not serialized — see [`builtin_scripts`]), `tags: HashSet<String>`, `name: Option<String>`. The optional `name` is validated for board-wide uniqueness at load time; the first claimant keeps the name and any later duplicate has its name cleared to `None` (nonfatal). `ObjectDef::new(x, y)` constructs with defaults (`z = 0`). `ObjectDef::default_glyph()` returns tile 63 (`?`) yellow on black.
**`kiln-core/src/layer.rs`** — palette layers (the map-file/draw-stack unit):
-`Layer { cells: Vec<(Glyph, Archetype)> }` (`pub(crate)`) — one row-major draw layer. A cell whose `glyph.tile == 0` (`Glyph::transparent()`) draws nothing, so the layer beneath shows through; solidity comes from the archetype, independent of transparency.
-`LayerData { content, fill, sparse, palette: HashMap<String, PaletteEntry> }` — serde for one `[[layers]]` entry. The grid comes from exactly one of three optional fields (precedence `content` → `fill` → `sparse`; none ⇒ all spaces): `content` (a multi-line grid string), `fill` (one char filling the whole grid — handy for a uniform floor layer), or `sparse` (a `Vec<SparseCell>` of `{ x, y, ch }` over an otherwise all-spaces grid — handy for a layer of just a few objects). Only `content` can mismatch the board dims (hard error); `fill`/`sparse` are always exactly sized (a bad `fill`/`ch` or out-of-bounds `sparse` cell is a nonfatal error). `PaletteEntry` is a single flat struct with a `kind: String` discriminator plus all-optional fields (`tile`, `fg`, `bg`, `generator`, `solid`, `opaque`, `pushable`, `script_name`, `tags`, `name`, `target_map`, `target_entry`); only the fields relevant to the kind are read. (One flat struct, not an enum, because `kind` is open-ended — any archetype name *or* a meta-kind.)
-`build_layer(data, w, h, &mut StdRand, &mut Vec<LogLine>) -> Result<(Layer, Vec<Placement>), String>` — resolves the palette (via `resolve_entry`), validates the grid dims (the only hard `Err`), and walks the grid building the `Layer` plus a `Vec<Placement>` (`Object(ObjectTemplate, x, y)` / `Portal(PortalTemplate, x, y)` / `Player(x, y)`) for the map loader to resolve across layers. Procedural floors roll a fresh glyph per cell from the shared seeded `StdRand`.
-`resolve_entry` maps `kind` → `Resolved`: `empty` → transparent cell; `floor` → a generator (per-cell roll) or a fixed visual-only `Empty` glyph; `object`/`portal`/`player` → a placement; any other string → `Archetype::try_from` (`Ok` → terrain cell; `Err` → visible `ErrorBlock` + logged error). A `portal` missing `name`/`target_map`/`target_entry` is dropped to a transparent cell with an error.
**`kiln-core/src/board.rs`** — the board data type:
-`Board` — the complete game unit (ZZT-style "board"): `width`, `height`, `layers: Vec<Layer>` (bottom→top draw stack; `pub(crate)`), `player: Player`, `objects: BTreeMap<ObjectId, ObjectDef>`, `next_object_id: ObjectId`, `portals: Vec<PortalDef>`, `board_script_name: Option<String>` (name of a board-level script in the world script pool, if any), `load_errors: Vec<LogLine>` (`pub(crate)`), `registry: HashMap<String, RegistryValue>`. Scripts are **not** stored on `Board` — they live in [`World::scripts`]. The visual floor is no longer a separate field: it is just `Empty` cells with a visible glyph on a lower layer.
-`glyph_at(x, y) -> Glyph` — the glyph a renderer should display at `(x, y)`. The player draws on top (returns `Glyph::player()` at its cell); otherwise layers are walked **top-down** and the first thing that draws wins: a solid object on that layer (always) or a visible non-solid object, else a portal on that layer, else the layer's terrain cell (a solid always draws; a non-solid only if `tile != 0`). Nothing anywhere → the canonical black `Empty` glyph. Front-ends call this per-cell instead of managing a separate player overlay.
-`solid_at(x, y) -> Option<Solid>` — the cell's single solid occupant (player checked first, then objects, then a solid terrain archetype on *any* layer via `solid_cell_layer`).
-`is_passable(x, y)` — convenience inverse of `solid_at`.
-`can_push(x, y, dir) -> bool` — read-only: does the chain of pushable solids end in open space?
-`can_shift(x, y, dir) -> bool` — read-only, one cell ahead only: `(x, y)` holds a pushable *and* the next cell is empty or another pushable (does **not** require the chain to end in open space, unlike `can_push`). The right gate for a simultaneous shift/rotation via `apply_swap`. Shifting onto the **player** counts only when the source is a `grab` thing (it gets grabbed, the player isn't moved); any other solid treats the player as a blocker.
-`push(x, y, dir)` — mutating: shoves the chain one step, leaving a transparent cell behind (so a lower floor layer is revealed). A pushed solid moves within its own layer (found via `solid_cell_layer`).
-`grab_object_at(x, y) -> Option<ObjectId>` (a solid `grab` object on the cell — the player-walks-onto-it case) and `pushed_grab_into_player(x, y, dir) -> Option<ObjectId>` (walk the pushable chain from `(x,y)`; if a chain cell is a `grab` object whose forward neighbour is the player, return it — the grab-thing-shoved-into-the-player case). `GameState` uses both to decide when to fire `grab()` instead of pushing/sliding the player. (`remove_object` only edits the `objects` map; a live `ScriptHost` keeps a stale `ObjectRuntime` whose later host-fn calls resolve to a missing id and no-op — benign.)
-`apply_swap(pairs: &[(i32,i32,i32,i32)]) -> (Vec<LogLine>, Vec<ObjectId>)` — applies a batch of one-way solid moves **simultaneously** (reads every source's solid occupant — player/object/terrain — into a private `SolidSnapshot` before writing any destination, so cycles and two-cell swaps resolve). A source with no solid moves an "empty", removing the destination's solid (terrain cleared; a displaced object despawned via `remove_object`). The **player is never destroyed** — a write that would overwrite it without relocating it is skipped + logged. A **grab** object whose destination is the player isn't written onto it — it is left in place and its id is returned (the second tuple element) so `GameState` fires its `grab()` hook (collected into the same `grabs` list as the push path). Because a grabbed object stays put (and its `grab()` may not despawn it), a final **overlap sweep** over the swapped cells keeps one solid per cell — preferring a grabbed object so its `grab()` can still fire — and deletes the rest (never the player), logging an error per deletion. Out-of-bounds entries are skipped + logged. Backs the script `swap()` fn.
-`place_archetype(x, y, arch, glyph)` — editor stamp primitive (used by kiln-tui's drawing tools). Keyed only on the archetype, leaving any floor untouched: a non-`Empty` (solid) arch removes a solid object in the cell then writes `(glyph, arch)` into the existing terrain layer (`terrain_layer_at`, the single non-`Empty` cell) or else the top layer; `Empty` erases — removes every object plus the terrain cell (→ transparent `Empty`). Note it writes **terrain** even for script-backed archetypes (pushers/spinners), so the editor stamps an inert cell — see `expand_builtin_archetypes`.
-`expand_builtin_archetypes()` — the **single** expansion point: replaces every script-backed terrain cell (e.g. `Spinner`/`Pusher`/`Gem`, those with an `archetype_script`) with the scripted object it expands to (embedded script + `BUILTIN_*` tag + behavior, copying the cell's glyph so palette overrides survive). The object's `pushable`/`grab` flags are taken from the archetype's `Behavior` (so a gem becomes pushable + grabbable; pushers/spinners stay unpushable). Idempotent (cells already loaded as objects are skipped). Called by `TryFrom<MapFile> for Board` after cross-layer validation (so disk loads get working machines) and again by the editor's `playtest()` on the `World::deep_clone` (so editor-stamped machines, which `place_archetype` writes as inert terrain, also run — the playtest skips the reload path). Because it runs after explicit-object placement, builtin objects get ids after hand-placed ones (still layer-then-reading order among themselves).
-`SpeechBubble { object_id, text, remaining }` — an active speech bubble created by a script's `say(s)` call. `remaining` counts down in `GameState::tick`; when it reaches zero the bubble is removed. At most one bubble per object (a new `say()` replaces the old one).
-`SAY_DURATION: f64` — how long a bubble lives (3.0 seconds).
-`Scroll { source: ObjectId, lines: Vec<ScrollLine> }` — an active scroll overlay opened by a script's `scroll(lines)` call. Lives on `GameState::active_scroll: Option<Scroll>`; front-ends pause ticks while it's `Some` and close it via `close_scroll(choice)`. `ScrollLine` is re-exported from `action.rs` through `game.rs` so front-ends import both from `kiln_core::game`.
-`GameState` — owns `world: World` (all boards as `Rc<RefCell<Board>>` + world scripts) and `current_board_name: String` (key of the active board). `pub log: Vec<LogLine>`, `scripts: ScriptHost`, `pub speech_bubbles: Vec<SpeechBubble>`, `pub active_scroll: Option<Scroll>`, `pub player_health: u32` (starts 5) and `pub player_gems: u32` (starts 0) — game-global player stats that persist across board transitions. `player_gems` is changed at runtime by the `add_gems(n)` script fn (e.g. grabbing a gem); `player_health` is still display-only. Front-ends reach the active board through `board() -> Ref<Board>` / `board_mut() -> RefMut<Board>` (both look up `world.boards[current_board_name]`). `current_board_name() -> &str` returns the active key. **`from_world(world: World) -> Self`** is the primary constructor: clones the start board's `Rc<RefCell<Board>>` for the `ScriptHost`, compiles scripts from `world.scripts`. `new(board)` and `with_scripts(board, scripts)` are `#[cfg(test)]`-only sugar that build a minimal single-board `World`. `try_move(dir)` moves the player (pushing if possible) and fires `bump(-1)` on any solid object walked into; walking onto a `grab` thing (via `Board::grab_object_at`) instead moves onto it and fires `grab()` + an immediate `resolve()` so its `die()`/`add_gems()` apply before the call returns (no player+object overlap). `run_init()` runs object `init()` hooks once at startup. `tick(dt)` advances cooldowns, expires speech bubbles, and runs `tick(dt)` hooks every frame. Both end by calling `resolve()`, which drains the board queue and applies each `Action` (`Log` → `log`, `SetTile` → source glyph, `Move(dir)` → `step_object`, `Say` → `speech_bubbles`, `Scroll` → `active_scroll`, `AddGems(n)` → `player_gems`, `Die` → `remove_object(source)`). `step_object` and `Action::Push` route a grab-thing-shoved-into-the-player (via `Board::pushed_grab_into_player`) into a deferred `grab()` instead of sliding the player, collected and fired in phase B alongside `bump`s. Resolution is two-phase: mutate the board collecting `(bumped, bumper)` pairs, drop the borrow, then fire `run_bump` for each pair. `drain_errors()` moves script errors into `log`. `close_scroll(choice)` clears `active_scroll` and optionally fires `run_send(source, choice, None)` to dispatch the player's selection back to the object.
**`kiln-core/src/action.rs`** — the `Action` enum and its Rhai-facing conversion:
-`MOVE_COST: f64` — how long a move occupies an object before it can act again (0.25 s).
-`ScrollLine` (`pub`) — one line of content in a `Scroll` action: `Text(String)` (plain, word-wrapped) or `Choice { choice, display }` (selectable; `choice` is sent back to the source object when the player picks it).
-`Action` (`pub(crate)`) — deferred mutation emitted by a script and applied by `GameState` after promotion onto the board queue: `Move(Direction)`, `SetTile(u32)`, `Log(LogLine)`, `SetTag { target, tag, present }`, `Say(String)`, `Delay(f64)` (never reaches the board queue — consumed by `ScriptHost::drain` to pace the object), `SetColor { fg, bg }`, `Send { target, fn_name, arg }`, `Scroll(Vec<ScrollLine>)`, `Teleport { x, y }`, `Push { x, y, dir }` (shove a chain at arbitrary coords; zero time cost), `Swap(Vec<(i32,i32,i32,i32)>)` (batch of simultaneous one-way solid moves; zero time cost), `AddGems(i64)` (change `GameState::player_gems`, clamped at 0; zero cost), `Die` (remove the source object; zero cost).
-`action_to_map(action) -> rhai::Map` — converts an `Action` to a Rhai map for `Queue.peek()` / `Queue.pop()`. The map always has a `"type"` key; other keys carry the payload. `Scroll`/`Swap` emit `type` only (their payloads are not inspectable via the map API). `Log` is flattened to its first span's text.
- A "floor" is just a non-solid, visible `Empty` cell on a layer (a palette entry with `kind = "floor"`). This module only owns the generators; the actual per-cell placement happens in `layer.rs` during load.
-`FloorGenerator` (`Grass`/`Dirt`/`Stone`) — procedural textures differing only in color scheme and texture-char probability. `from_name(&str)` parses the map-file name; `generate(&mut StdRand)` picks a dark, low-saturation ground color (green/brown/gray) and, with the generator's probability, scatters a lighter texture char (grass `, . \` '`; dirt `. : , ;`; stone `. ,`). Uses `tinyrand` (already a workspace dep, WASM-safe). `FLOOR_SEED` (`pub(crate)`) seeds one `StdRand` per board build (in `map_file`), threaded through every generator call, so floors are deterministic/testable and depend only on map content.
**`kiln-core/src/log.rs`** — styled log messages:
-`LogSpan { text, fg: Option<Rgba8>, bg: Option<Rgba8> }` and `LogLine { spans: Vec<LogSpan> }` — a UI-agnostic styled message (colors are core `Rgba8`, not a front-end type). `LogLine::raw()`, a chainable `push()`, `append()`, and `LogLine::error()` (a red-on-black single-span constructor used for nonfatal load errors) build messages; each front-end converts a `LogLine` to its own styled text at render time.
**`kiln-core/src/script.rs`** — Rhai scripting runtime:
-`ScriptHost` — owns the Rhai `Engine`, the compiled scripts referenced by a board's objects, a per-object persistent `Scope` + output queue + ready timer, and the shared board queue. Built with `ScriptHost::new(&Rc<RefCell<Board>>, &HashMap<String, String>)`: the first arg is a shared ref to the active board (used by read-API closures), the second is the world-level script pool. Each object resolves to a `(key, source)` compiled once per key: a named script keys by its pool name; an object's embedded `builtin_script` keys by its source text (so identical built-ins, e.g. all pushers, share one AST). Reports compile/unknown-script failures onto the error sink; runs nothing.
- Lifecycle hooks per object: `init()` (zero-arg), `tick(dt)` (elapsed seconds as `f64`), `bump(id)` (the bumper's `ObjectId`, or `-1` for the player), and `grab()` (zero-arg; fired when the player walks onto / pushes a `grab` thing into themselves), all optional — detected via `AST::iter_functions()` by name and arity. Driven by `run_init()` / `run_tick(dt)` / `run_bump(object_id, bumper)` / `run_grab(object_id)`; runtime errors go to the error sink (drained to the log), not fatal.
- **Reads (direct):** read getters (`player_x`, `player_y`, `width`, `height`) are registered on `Rc<RefCell<Board>>` (the `BoardRef` alias, exposed to Rhai under the type name `Board`) — getters only, so read-only by construction. A clone of the handle is pushed into each scope as the constant `Board`. `blocked(dir) -> bool` is also a read fn: true if the caller's target cell is off-board, already solid, or the destination of a pending move on the board queue (an object never sees its *own* move, which is pumped only after its script returns). `can_push(x, y, dir) -> bool` is a read fn mirroring `Board::can_push`: true if `(x, y)` holds a pushable whose chain can be shoved in `dir` (false off-board). `can_shift(x, y, dir) -> bool` mirrors `Board::can_shift`: like `can_push` but only checks the single cell ahead (pushable source + an empty-or-pushable next cell), the right gate for a simultaneous shift/rotation via `swap`. `passable(x, y) -> bool` mirrors `Board::is_passable`: true if `(x, y)` is on-board and holds no solid (off-board → false), letting a script tell a hole apart from a blocked solid (which `can_shift`/`can_push` alone cannot). `has_tag(s) -> bool` and `get_tags() -> Array` read the calling object's tag set; `objects_with_tag(s) -> Array` returns all object ids carrying that tag. `my_name() -> String` returns the calling object's name (or `""` if unnamed); `object_id_for_name(s) -> i64` looks up an object by name and returns its id, or `0` if not found. Each getter briefly borrows the shared `Board`.
- **Actions & rate limiting (two-tier queues):** host fns `move(dir)`, `set_tile(n)`, `log(s)`, `say(s)`, `scroll(lines)`, `push(x, y, dir)`, `swap(pairs)`, `add_gems(n)` (adjust the player's gem count), `die()` (remove the calling object) append an `Action` (`Move`/`SetTile`/`Log`/`Say`/`Scroll`/`Push`/`Swap`; `MOVE_COST = 0.25` s for `Move`, else 0 — `push`/`swap` add no delay) to the *issuing object's* output queue (routed by the per-call tag via a `HashMap<usize, ObjQueue>`). `scroll(lines)` takes a Rhai array where each element is a string (text line) or a two-element array `[choice_key, display_text]` (selectable choice). `push(x, y, dir)` shoves the pushable chain at arbitrary coords `(x, y)`. `swap(pairs)` takes an array of four-int `[src_x, src_y, dst_x, dst_y]` arrays (a malformed entry is skipped + logged) and moves all the named solids simultaneously (see `Board::apply_swap`). `ScriptHost::pump(i)` promotes ready actions onto the shared **board queue** (`Vec<BoardAction { source, action }>`): the leading run of zero-cost actions plus at most one timed action, which arms that object's **ready timer** and ends the pump. While a ready timer is `> 0` nothing is pulled (this caps object speed); `advance_timers(dt)` counts them down each frame. `GameState` drains the board queue with `take_board_queue()` and applies it after the batch — so scripts mutate without a `&mut GameState` borrow. Errors (compile/runtime) bypass the queues via the error sink (`take_errors()`).
- The `Queue` object (a handle to the calling object's output queue) is pushed into each scope; scripts call `Queue.length()`, `Queue.clear()`, `Queue.peek()` (front action as a Rhai map, or `()` if empty), and `Queue.pop()` (same, removes the front). Safe to mutate from script because the host only touches output queues between calls (during `pump`).
- **Sender identity:** `source` (which object issued an action) rides the per-call **tag** — `run` calls `call_fn_with_options(...with_tag(object_id)...)` and the host fns read it via `NativeCallContext::tag()` (decoded back to an `ObjectId` by `source_of`). Scripts write `move(North)` without naming themselves; `North`/`South`/`East`/`West` are `Direction` constants in scope, and `impl From<Direction> for (i32,i32)` gives the delta.
-`GameState` (hence the `Engine`/`Scope`) is single-threaded / not `Send`; fine for kiln-tui.
- **Sender identity uses stable ids:** `BoardAction.source`, `ObjectRuntime.object_id`, and the `QueueMap` keys are all the object's `ObjectId` (matching `Board::objects`' `BTreeMap` keys), so they survive object spawn/destroy/reorder. The per-call tag carries the id as an `i64` (id 0 — never valid — is the no-source fallback). `ScriptHost::objects` is still a `Vec<ObjectRuntime>` built by iterating the board map, so it stays in ascending-id order.
**`kiln-core/src/map_file.rs`** — per-board serde shell + load/save orchestration (the bulk of the per-layer work lives in `layer.rs`):
-`MapFile { map: MapHeader, layers: Vec<LayerData> }` — serde for one board: a `[map]` header (`name`, `width`, `height`, optional `board_script_name`; **no**`player_start` — the player is a `kind = "player"` palette char) plus the `[[layers]]` stack. Does **not** include scripts (those live in `World::scripts`).
-`TileIndex` (`pub`) — `#[serde(untagged)]` enum accepting either `Num(u32)` or `Chr(char)`; lets map files use `tile = " "` (char) or `tile = 32` (integer) interchangeably. `parse_color`/`color_to_hex` (`pub(crate)`) are shared with `layer.rs`.
-`impl TryFrom<MapFile> for Board` — the load conversion: builds each layer via `layer::build_layer` (collecting object/portal/player placements with their layer `z`), then runs the cross-layer validations. **Best-effort/nonfatal**: only a layer grid-dimension mismatch returns `Err`; everything else is recorded on `Board::load_errors` (see `Board::is_valid`) — the player must appear exactly once (missing → `(0,0)`; multiple → first) and *wins* its cell; one solid per cell across all layers (a stacked solid is dropped); object names board-unique (a dup is cleared), portal names unique (a dup is dropped). Object ids are assigned in layer-then-reading order. Finally it calls `Board::expand_builtin_archetypes` to turn script-backed archetype cells (pushers/spinners) into their scripted objects (these get ids after the hand-placed objects).
-`impl From<&Board> for MapFile` — save: emits one `[[layers]]` per board layer (deduping each unique `(Glyph, Archetype)` to a palette char), with objects/portals grouped by `z` and the player written onto the top layer. Generators baked to literal glyphs at load are saved as fixed `floor` glyphs (the generator name is not recovered).
-`pub fn load(path: &str) -> Result<Board, …>` — reads a single-board `.toml` file. Production code uses `world::load` instead.
-`pub fn save(board: &Board, path: &Path) -> Result<(), …>` — serializes `Board` back to a single-board TOML file.
**`kiln-core/src/world.rs`** — world type and world-file loading:
-`World` — the runtime representation of a `.toml` world file: `name: String`, `start: String` (key of the starting board), `scripts: HashMap<String, String>` (named Rhai source, shared across all boards), `boards: HashMap<String, Rc<RefCell<Board>>>` (all boards, always present). Every board is wrapped in `Rc<RefCell<Board>>` so multiple shared refs can coexist — `GameState` clones the active board's `Rc` for its `ScriptHost`, and all boards remain in `world.boards` at all times (no board is ever "removed" when active).
-`pub fn load(path: &str) -> Result<World, Box<dyn std::error::Error>>` — reads a world `.toml` file, converts each `[boards.NAME.*]` subtable via `TryFrom<MapFile> for Board`, wraps each in `Rc::new(RefCell::new(...))`, and validates that `world.start` matches a board key.
-`pub fn deep_clone(&self) -> World` — a **fully independent** copy: rebuilds every board into a *fresh*`Rc<RefCell<Board>>` (`Board`/`Layer`/`ObjectDef` derive `Clone`) rather than sharing the `Rc`s. An explicit method, not a `Clone` impl, since shallow `Rc`-sharing would be a footgun. Used by the editor's playtest to run a game against an isolated world so play mutations never touch the boards being edited.
