334 lines
53 KiB
Markdown
334 lines
53 KiB
Markdown
# CLAUDE.md
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This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
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## Project
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`kiln` is a ZZT-inspired game-making system written in Rust (edition 2024) — a runtime **and** authoring environment where game worlds are plain-text files with embedded scripts. The model is ZZT (1991, Epic MegaGames): a DOS game that shipped with a built-in editor and a scripting language (ZZT-OOP), letting players create and share worlds. ZZT's playfield was 60×25 characters; each board was a self-contained screen with scripted objects, passages to adjacent boards, and ~50 built-in element types.
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**Tech-stack rationale (the "why"):**
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- **WASM compatibility is a first-class requirement** — everything in the stack must compile to WASM. This is why scripting uses **Rhai** (pure Rust, sandboxed, no C deps, explicit WASM support) rather than Lua (which needs C FFI via mlua/rlua).
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- **Maps are TOML + serde** — human-readable, hand-editable, good Rust tooling; grid multi-line strings make the room shape visible, and embedded Rhai scripts fit TOML multi-line strings without escaping.
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- **The engine (`kiln-core`) is UI-agnostic** — no rendering/UI types leak in (e.g. log colors are core `Rgba8`, not a front-end type), so the same game data drives multiple front-ends. kiln-tui being added with zero engine changes is the proof.
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## Code style
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- Add `///` rustdoc comments to every `pub` type, field, and function. The user reads rustdoc in their IDE to understand the code while making changes.
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- Add inline `//` comments inside non-trivial function bodies to explain the *why* of each logical step — especially in `update` loops, rendering math, and conversion logic.
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- Keep comments accurate: update them when the code they describe changes.
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## Finishing an epic
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When the user says **"finish the epic"**, do all of the following in order:
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1. Update `CLAUDE.md` to reflect any new modules, types, or behaviors added during the session.
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2. Run the `/simplify` skill on changed code.
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3. Commit everything with a summary message.
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## Commands
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```bash
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cargo build # compile the workspace (kiln-core + kiln-ui + kiln-tui)
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cargo run -p kiln-tui -- maps/start.toml # play/edit a world in the terminal
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cargo test # run all tests
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cargo test <name> # run a single test by name (substring match)
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cargo clippy # lint
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cargo fmt # format
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```
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## Architecture
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`kiln` is a Cargo **workspace** that separates the engine from its front-ends so the same game data can be driven by different UIs:
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- **`kiln-core`** — 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.
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- **`kiln-ui`** — reusable, **game-agnostic** terminal UI widgets on **ratatui** (no `kiln-core` dep). Each widget owns its presentation + input handling and is generic over a host context `Ctx` it mutates only through callbacks. Currently holds the dialog/text-field system (`dialog::Dialog<Ctx>`) and the shared `dim_area` overlay helper; future home of the script text-editor wrapper.
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- **`kiln-tui`** — a terminal **player + world editor** built on **ratatui 0.30 / crossterm**, depending on both `kiln-core` and `kiln-ui`. Takes a world-file path on the command line; plays a board (arrow keys) and edits it (`Esc` → menu → `e`).
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Root `Cargo.toml`: `members = ["kiln-core", "kiln-tui", "kiln-ui"]`, with `ratatui`/`tui-input` pinned in `[workspace.dependencies]` so kiln-ui and kiln-tui share one version (their public APIs exchange ratatui types).
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### kiln-core modules
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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.
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**`kiln-core/src/glyph.rs`** — per-cell visual:
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- `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`.
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**`kiln-core/src/archetype.rs`** — element taxonomy:
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- `Archetype` (`Copy`, `PartialEq`, `Hash`) — enum of named element types: `Empty`, `Wall`, `Crate`, `HCrate`, `VCrate`, `Pusher(Direction)`, `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. `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`).
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**`kiln-core/src/builtin_scripts.rs`** — archetypes that are really scripted objects (`pub(crate)`):
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- `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`. When `resolve_entry` (in `layer.rs`) hits such an archetype it emits an `ObjectDef` carrying that source in `builtin_script` plus a `BUILTIN_<archetype>` tag instead of a terrain cell.
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- `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.
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**`kiln-core/src/utils.rs`** — shared primitive types (`pub(crate)`):
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- `Pushable` (`No`/`Any`/`Horizontal`/`Vertical`) — which directions a solid may be pushed. `allows(dir) -> bool`.
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- `Behavior` — plain data struct from `Archetype::behavior()`: `solid: bool`, `opaque: bool`, `pushable: Pushable`.
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- `ObjectId = u32` — stable identifier for board objects.
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- `Solid` — the single solid occupant of a cell, returned by `Board::solid_at`: `Player`, `Cell(Archetype)`, or `Object(ObjectId)`.
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- `Player { x: i32, y: i32 }` — current player position.
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- `PortalDef { x, y, target_map, target_entry }` — parsed from map files, not yet runtime-wired.
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**`kiln-core/src/object_def.rs`** — scripted objects (`pub(crate)`):
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- `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`), `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.
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**`kiln-core/src/layer.rs`** — palette layers (the map-file/draw-stack unit):
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- `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.
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- `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.)
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- `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`.
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- `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.
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**`kiln-core/src/board.rs`** — the board data type:
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- `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.
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- `layer_count() -> usize`; `get(z, x, y) -> &(Glyph, Archetype)` / `get_mut(z, x, y)` — per-layer cell access (panics OOB).
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- `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.
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- `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`).
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- `is_passable(x, y)` — convenience inverse of `solid_at`.
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- `can_push(x, y, dir) -> bool` — read-only: does the chain of pushable solids end in open space?
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- `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`).
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- `add_object(obj) -> ObjectId`, `object_ids_at(x, y)`, `solid_object_id_at(x, y)` — object queries.
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- `in_bounds((i32, i32))` — bounds-checks a possibly-negative coord.
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- `is_valid()` / `load_errors()` / `report_error(msg)` — nonfatal load-error surface.
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**`kiln-core/src/game.rs`** — game-loop logic only:
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- `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).
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- `SAY_DURATION: f64` — how long a bubble lives (3.0 seconds).
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- `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`.
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- `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>`. 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. `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`). 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.
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**`kiln-core/src/action.rs`** — the `Action` enum and its Rhai-facing conversion:
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- `MOVE_COST: f64` — how long a move occupies an object before it can act again (0.25 s).
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- `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).
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- `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>)`.
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- `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` emits `type` only (lines are not inspectable via the map API). `Log` is flattened to its first span's text.
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**`kiln-core/src/floor.rs`** — procedural floor generators:
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- 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.
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- `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.
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**`kiln-core/src/log.rs`** — styled log messages:
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- `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.
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**`kiln-core/src/script.rs`** — Rhai scripting runtime:
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- `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.
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- Lifecycle hooks per object: `init()` (zero-arg), `tick(dt)` (elapsed seconds as `f64`), and `bump(id)` (the bumper's `ObjectId`, or `-1` for the player), all optional — detected via `AST::iter_functions()` by name and arity. Driven by `run_init()` / `run_tick(dt)` / `run_bump(object_id, bumper)`; runtime errors go to the error sink (drained to the log), not fatal.
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- **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). `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`.
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- **Actions & rate limiting (two-tier queues):** host fns `move(dir)`, `set_tile(n)`, `log(s)`, `say(s)`, `scroll(lines)` append an `Action` (`Move`/`SetTile`/`Log`/`Say`/`Scroll`; `MOVE_COST = 0.25` s for `Move`, else 0) 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). `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()`).
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- 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`).
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- **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.
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- `GameState` (hence the `Engine`/`Scope`) is single-threaded / not `Send`; fine for kiln-tui.
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- **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.
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**`kiln-core/src/map_file.rs`** — per-board serde shell + load/save orchestration (the bulk of the per-layer work lives in `layer.rs`):
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- `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`).
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- `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`.
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- `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.
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- `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).
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- `pub fn load(path: &str) -> Result<Board, …>` — reads a single-board `.toml` file. Production code uses `world::load` instead.
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- `pub fn save(board: &Board, path: &Path) -> Result<(), …>` — serializes `Board` back to a single-board TOML file.
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**`kiln-core/src/world.rs`** — world type and world-file loading:
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- `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).
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- `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.
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### kiln-ui modules
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Reusable, **game-agnostic** terminal UI widgets on **ratatui** — no `kiln-core` dependency. A widget owns its presentation + input handling and is generic over a host context `Ctx` it mutates *only through callbacks*, so a front-end decides what a choice does without the widget knowing about game/world types. The front-end owns the event loop and routes input to the widget while it is focused.
|
||
|
||
**`kiln-ui/src/lib.rs`** — crate root:
|
||
- `dim_area(area, buf)` (`pub`) — dims every cell in `area` (background tint for a modal overlay). Shared scaffolding: used by [`dialog`] here and re-borrowed by kiln-tui's `overlay::render_overlay_frame` so both modal styles dim identically.
|
||
- `pub mod dialog;` — see below. (Future home of a full-screen script text-editor wrapper.)
|
||
|
||
**`kiln-ui/src/dialog.rs`** — modal dialog widgets, backed by [`tui-input`]:
|
||
- `Dialog<Ctx>` — an open dialog generic over the host context its callback mutates. Built via `Dialog::text(title, initial, on_done)` (a single free-text field; `on_done: FnOnce(Option<String>, &mut Ctx)`, `None` on cancel) or `Dialog::list(title, items, allow_create, on_done)` (a filter field over a selectable list; `on_done: FnOnce(ListDialogResponse, &mut Ctx)`). Holds a `DialogBody` (`Text`/`List`) plus the boxed callback. The text field is a `tui_input::Input` driven through `InputRequest` (we don't use tui-input's own event backend, avoiding crossterm-version coupling).
|
||
- `ListDialogResponse { Select(String), Create(String), Cancel }` — list outcome: an existing entry, a newly-typed value (only when `allow_create`), or cancel. `DialogResult { Continue, Submit, Cancel }` — what a key event did.
|
||
- `handle_event(&Event) -> DialogResult` — `Esc`→`Cancel`; `Enter`→`Submit` only when OK is enabled (always for text; for a list, a valid entry is selected *or* `allow_create` + non-empty); Up/Down move a list's selection; other keys edit the field (and re-clamp the list selection to the new prefix filter). `finish(result, &mut Ctx)` consumes the dialog and fires its callback. The host pattern: `take()` the dialog out of its slot on `Submit`/`Cancel`, then call `finish` so the callback gets an un-borrowed `&mut Ctx`.
|
||
- `Dialog::draw(&self, &mut Frame)` — dims the screen, draws a centered bordered box. A **text** dialog centers its field box (h+v) with a distinct `FIELD_BG` background so it reads as an input box; a **list** dialog puts the filter field atop the scrolling, selection-highlighted list. Both show an `[enter] OK [esc] Cancel` footer (OK dimmed when disabled). Takes `&mut Frame` (not a `Widget`) because it needs to place a real terminal cursor. Unit-tested (filtering/clamping, OK-enabled rule, Select/Create/Cancel/text outcomes) with a dummy `Ctx`.
|
||
|
||
### kiln-tui modules
|
||
|
||
The terminal **player + world editor**, depending on both `kiln-core` and `kiln-ui`. Renders the board as text: each `Glyph.tile` index is reinterpreted as a character (the default kiln font is CP437, where the tile index equals the code point) and drawn with the glyph's RGB colors. No bitmap font or UV mapping is involved. The app is one of two top-level [`Mode`]s — `Play` (live, ticking game) or `Edit` (a freshly reloaded, non-ticking world) — and the active mode plus a `Ui` value are threaded through the loop.
|
||
|
||
**Drawing rule: prefer ratatui primitives.** Before writing manual cell-by-cell buffer code, check whether a `Block`, `Paragraph`, `Layout`, `Line::centered()`, or other ratatui widget/method achieves the same result. If a small design change (e.g. fixed vs. content-driven sizing) would unlock a ratatui-native approach, raise it as a question rather than writing manual code. The documented exceptions are: the background dimming pass (`kiln_ui::dim_area`, used by `render_overlay_frame` and the dialog widgets — no ratatui primitive for "tint the whole buffer"); the tail characters in `SpeechBubblesWidget` (`speech.rs`): the tail-join `┬` on the bottom border and the `│` column drawn below the box down to the source object; and the blinking editor cursor + LFSR wipe blend.
|
||
|
||
**`kiln-tui/src/main.rs`** — entry point, real-time loop, and frame dispatch:
|
||
- Parses a single positional arg (the world file path); prints usage and exits non-zero if missing. Loads the world via `kiln_core::world::load` *before* touching the terminal so load errors print to a normal screen, then `GameState::from_world(world)`, wrapped in `Mode::Play`. The world path is kept on `Ui::world_path` so the editor / play-reload can reload it.
|
||
- `ratatui::init()` → `EnableMouseCapture` → detect `TerminalCaps` → push Kitty flags when supported → `run` loop → pop Kitty flags → `DisableMouseCapture` → `ratatui::restore()`. `game.run_init()` runs object `init()` hooks before the loop.
|
||
- `run` is a ~30 FPS real-time loop: `event::poll`s only until the next frame deadline (so input stays responsive) and otherwise wakes to advance by the real elapsed `dt` via `Ui::tick(dt, mode)`. Acts on `Press`/`Repeat` and ignores `Release` (the Kitty protocol emits these; acting on them double-fires moves). Input is routed by `current_input_mode`: `Menu`→`handle_menu_input`; otherwise (unless `Ignore`) it matches on `Mode` — `Play` → `handle_board_input`/`handle_scroll_input`, `Edit` → `handle_editor_input`/`handle_dialog_input`. After ticking it calls `apply_pending_mode` and exits once `should_quit` is set and no close animation is running.
|
||
- `apply_pending_mode(mode, ui)` — applies a `PendingMode` a menu action requested: reloads the world from `world_path` and swaps `*mode` to `Mode::Edit(EditorState::new(world))` (enter editor) or a fresh `Mode::Play` (play world, re-running `init()`); a reload failure is logged to the play game and leaves the mode unchanged.
|
||
- `draw(frame, mode, ui)` — renders the active mode (`draw_play` or `editor::draw_editor`), then the overlay layer in precedence **animation > menu > (Play: scroll / Edit: dialog)**: an `Overlay`-layer animation via `AnimWidget`, else `MenuWidget`, else the play scroll overlay (`ScrollOverlayWidget`) or the editor dialog (`kiln_ui::dialog::draw`). `draw_play` wraps the board in a bordered `Block` (board-name title; latest log previewed in the bottom border when the panel is closed). `draw_board_area` initializes a pending portal transition (now that the inner area is known) and renders either the board-layer wipe animation or the live board + speech bubbles.
|
||
|
||
**`kiln-tui/src/mode.rs`** — top-level application mode:
|
||
- `Mode { Play(GameState), Edit(EditorState) }` — exactly one is live at a time (play and edit are mutually exclusive: entering the editor drops the running game; returning to play rebuilds it fresh from the world file). `PendingMode { EnterEditor, PlayWorld }` — a deferred Play↔Edit switch requested by a menu closure (which only has `&mut Ui`) and applied by the run loop, mirroring the `should_quit` pattern.
|
||
|
||
**`kiln-tui/src/editor.rs`** — world editor mode:
|
||
- `EditorState` — a non-ticking editing session over a freshly reloaded `World`: `world`, `board_name` (board being edited), `menu: Vec<MenuLevel>` (sidebar menu stack, for breadcrumb + escape-to-parent), `dialog: Option<Dialog<EditorState>>`, a blinking `cursor`, `sidebar_width` (mouse-resizable), blink state, `last_board_area` (written at draw, read for right-click hit-testing), and editor-side `log`.
|
||
- `MenuLevel { World }` — a sidebar menu level; `title()` (breadcrumb segment) and `choices()` (static `(key, label)` list — `[n] Name`, `[e] Entry board`, `[s] Scripts`, `[b] Boards`). The menu is a stack so nested levels can be added later; today only `World` exists and every choice opens a dialog (no sub-menu). Per the design, menus are static letter-keyed lists — picking from a list is always a dialog, so arrow keys never conflict with the board cursor.
|
||
- Methods: `breadcrumb()`, `current_menu()`, `menu_escape(ui)` (pop a level, or at the root open the overlay `editor_menu_items()`), `menu_key(c)` (dispatch a letter → `open_*_dialog`), `menu_value(key)` (the "current value" shown beneath a choice in the sidebar — world name for `n`, start board for `e`), and the `open_{name,entry,scripts,boards}_dialog` builders (name → text dialog writing `world.name`; entry → list dialog writing `world.start`; scripts/boards → select-only list dialogs for now).
|
||
- `editor_menu_items()` — the overlay editor menu (`[p]` play, `[q]` quit, `[esc]` resume), opened at the root of the menu tree. `handle_dialog_input(event, ed)` — forwards to the open dialog and, on `Submit`/`Cancel`, `take`s it out and calls `finish(.., ed)`. `draw_editor(frame, ed, ui)` / `editor_layout(..)` — board (with blinking cursor + coord readout), a resizable right-hand sidebar (breadcrumb title + the menu choices, each with its optional current-value line), and the optional full-width log panel.
|
||
|
||
**`kiln-tui/src/ui.rs`** — front-end presentation state (not on `GameState`):
|
||
- `Ui { log: LogState, overlay: ScrollOverlayState, pending_transition, active_animation: Option<Box<dyn Animation>>, menu: Option<MenuState>, should_quit, world_path, pending_mode }`. While `active_animation` is `Some` all input is suppressed. `tick(dt, mode)` advances the active animation (and, on completion, clears scroll/menu state when returning to `Board`), then ticks the active mode — the game only in `Play` + `Board` input mode (so an open scroll/menu pauses it), the editor's cursor blink in `Edit`; a scroll that appears from a tick starts an open animation.
|
||
- `open_menu(items)` / `begin_close_menu()` — start the menu open/close animations (snapshotting `MenuState`). `begin_close(choice, game)` — set the player's scroll choice and start the scroll close animation. `start_transition(old, new, area)` — build the board-wipe once the inner area is known. `scroll_lines(delta)` / `scroll_menu(delta)` — clamped overlay/menu scrolling.
|
||
|
||
**`kiln-tui/src/input.rs`** — input mode + dispatch:
|
||
- `InputMode { Board, Scroll, Menu, Editor, Dialog, Ignore, Frozen }`. `current_input_mode(mode, ui)` — derives the mode: an active animation declares its own (`input_mode_during`); a pending transition → `Ignore`; an open `ui.menu` → `Menu`; else from `Mode` (`Edit` → `Dialog` when a dialog is open else `Editor`; `Play` → `Scroll` when a scroll is active else `Board`).
|
||
- `handle_board_input` (arrows move the player via `try_move_with_transition`, `l` toggles log, `Esc` opens the `pause_menu_items()` overlay, PageUp/Down + mouse scroll/resize the log), `handle_editor_input` (arrows move the cursor, `l` toggles log, `Esc` → `menu_escape`, letters → `menu_key`, right-click moves the cursor, drag resizes the sidebar), `handle_scroll_input` (scroll nav + choice letters via `resolve_choice`), `handle_menu_input` (clone the matched item's action `Rc` to drop the `ui.menu` borrow, then call it). `try_move_with_transition` captures both board `Rc`s into `ui.pending_transition` when a move crosses a portal.
|
||
|
||
**`kiln-tui/src/animation.rs`** — the animation abstraction:
|
||
- `Animation` trait — `update(dt) -> bool` (done?), `draw(area, buf)`, `layer()`, `input_mode_during()` (default `Ignore`), `input_mode_after()`. `AnimationLayer { Board, Overlay }` (board-area replacement vs. full-screen overlay). `AnimWidget<'a>(&'a dyn Animation)` — adapts an animation to a ratatui `Widget` for `frame.render_widget`.
|
||
|
||
**`kiln-tui/src/transition.rs`** — board-change wipe:
|
||
- `TransitionAnimation` — pre-renders the old and new boards into off-screen `Buffer`s, then reveals cells in an LFSR-driven pseudo-random order over `TRANSITION_DURATION` (0.25 s), blending old/new per cell in `draw`. A `Board`-layer animation that ends in `InputMode::Board`. `lfsr_step`/`lfsr_sequence` build the maximal-period permutation (16-bit Galois LFSR, poly `0xB400`).
|
||
|
||
**`kiln-tui/src/overlay.rs`** — shared overlay window frame:
|
||
- `OverlayStyle { bg, border_fg, width_div, height_fraction }` and `render_overlay_frame(style, progress, area, buf) -> Option<(content_rect, scrollbar_rect)>` — dims the background (via `kiln_ui::dim_area`), sizes/centers an animated-height window (kept even), draws the bordered block, and returns the content + scrollbar rects. Shared by `menu.rs` and `scroll_overlay.rs`. (The dialog widgets in kiln-ui draw their own smaller box and only reuse `dim_area`.)
|
||
|
||
**`kiln-tui/src/menu.rs`** — in-game menu overlay:
|
||
- `MenuItem { key: MenuKey, label, action: Rc<dyn Fn(&mut Ui)> }` (`ActionRc`) and `MenuKey { Char(char), Esc }` — menu actions only touch `Ui` (signal close/quit/`pending_mode`), so the same shape works for play and editor menus. `MenuState { items, offset, max_scroll }`, `MenuWidget` (fully-open `StatefulWidget`), and `MenuOpenAnimation`/`MenuCloseAnimation` (share the `Animation` pipeline + `render_overlay_frame`, blue style). `render_menu_at(..)` draws one `[key] label` line per item. `pause_menu_items()` — the play-mode pause menu (`[e]` edit, `[q]` quit, `[esc]` close).
|
||
|
||
**`kiln-tui/src/scroll_overlay.rs`** — scroll overlay widget:
|
||
- `ScrollOverlayState { offset, max_scroll }` — input/output state threaded through render. `ScrollOverlayWidget<'a>` — `StatefulWidget` for the fully-open overlay (½ width × ¾ height, amber style); `ScrollOpenAnimation`/`ScrollCloseAnimation` implement `Animation` for the open/close transitions. `render_scroll_at(..)` wraps text, centers whitespace-leading lines, prefixes choices with `[a]`/`[b]`, and draws a scrollbar when content overflows.
|
||
|
||
**`kiln-tui/src/cp437.rs`** — CP437 → Unicode mapping:
|
||
- `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 the table for `tile < 256`; falls back to `char::from_u32` then a blank space. Unit-tested.
|
||
|
||
**`kiln-tui/src/render.rs`** — board → ratatui buffer:
|
||
- `BoardWidget<'a>` — a `ratatui::widgets::Widget` that draws the board. Per axis, `axis(board_len, view, player) -> (offset, pad, count)` (pub): a board smaller than the viewport is **centered** with screen padding, a larger one **scrolls** to keep the player on screen with no empty margins. Each cell calls `Board::glyph_at`, which already folds in the player glyph at the player's position — no separate player-overlay pass needed.
|
||
- `board_to_screen(area, board, bx, by) -> Option<(u16, u16)>` and its inverse `screen_to_board(area, board, sx, sy) -> Option<(usize, usize)>` (pub) — convert between board cells and terminal coordinates using the same `axis` math, returning `None` off-board. Used by the editor's blinking cursor + right-click hit-testing (and mirrored by `speech::board_screen_pos`).
|
||
|
||
**`kiln-tui/src/speech.rs`** — speech bubble widget:
|
||
- `SpeechBubblesWidget<'a>` — a `ratatui::widgets::Widget` that draws speech bubbles for all active `SpeechBubble`s over the board. Two-pass: first collects all placements (sorted bottom-first so upward-shift decisions don't interfere with higher bubbles), then renders in **reverse** order (top-most first) so lower bubbles' boxes naturally cover extended tails without an explicit occlusion check.
|
||
- Each bubble: `Block::bordered()` + `Paragraph` for the box; the tail-join `┬` on the bottom border and a column of `│` chars from below the box down to the source object are written manually. Bubbles that would overlap are shifted upward one row at a time (up to 20 attempts) until clear.
|
||
- `place_bubble(area, obj_sx, obj_sy, lines, placed) -> Option<Rect>` — sizes and places one bubble, appending its rect to `placed` on success.
|
||
- `board_screen_pos(area, board, bx, by) -> Option<(u16, u16)>` — converts a board cell coordinate to terminal screen coordinates, returning `None` if off-screen. Used by bubble placement.
|
||
|
||
**`kiln-tui/src/log.rs`** — log panel widget:
|
||
- `LogState { open, height, scroll }` — panel visibility, height in rows, and scroll offset. `toggle()`, `scroll_by(delta, log_len)`, `resize(target, total)`.
|
||
- `LogWidget<'a>` — `StatefulWidget` that renders all log lines newest-first in a bordered block with word-wrap.
|
||
- `logline_to_line(line) -> Line` — converts a core `LogLine` into a styled ratatui `Line`; each `LogSpan`'s optional fg/bg is applied only when present.
|
||
- `log_preview_line(logs) -> Line` — builds the `[l]og: <latest>` preview span for the board's bottom border.
|
||
|
||
**`kiln-tui/src/utils.rs`** — shared rendering helpers:
|
||
- `rgba8_to_color(Rgba8) -> Color` — lossless RGB bridge (alpha dropped).
|
||
- `rects_overlap(a, b) -> bool` — true if two `Rect`s share at least one cell; used by bubble placement.
|
||
|
||
**`kiln-tui/src/term.rs`** — terminal capability detection and Kitty setup:
|
||
- `TerminalCaps { keyboard_enhancement: bool, truecolor: bool }` — detected once at startup. `keyboard_enhancement` is a real query/response (`supports_keyboard_enhancement()`); `truecolor` reads `$COLORTERM`. Intended to be handed to scripts so they can pick bindings the terminal actually supports.
|
||
- `summary_line() -> Line` — styled one-line badge for the bottom border; when `truecolor`, the word "truecolor" is drawn with each letter a different rainbow color (`hue_to_rgb`, an HSV→RGB helper), else a plain "256-color".
|
||
- `push_kitty_flags()` / `pop_kitty_flags()` — enable/disable the Kitty keyboard protocol (`DISAMBIGUATE_ESCAPE_CODES | REPORT_EVENT_TYPES | REPORT_ALTERNATE_KEYS | REPORT_ALL_KEYS_AS_ESCAPE_CODES`); the last flag makes modifier-only keypresses observable. Pushed only when supported, popped before restore. Enabling `REPORT_EVENT_TYPES` is why the input loop must filter out `Release` events.
|
||
|
||
### World file format (`maps/*.toml`)
|
||
|
||
Each `.toml` file is a **world**: a named collection of boards plus a shared script pool. The `[world]` header names the world and designates the starting board. Scripts live once at the top level and are referenced by name from any board's objects. Each board lives under `[boards.NAME.*]` where `NAME` is the board's identifier string.
|
||
|
||
**Keep this example in sync with `world.rs` / `map_file.rs` whenever the format changes.**
|
||
|
||
A board is a `[map]` header plus an **ordered array of `[[layers]]`** (bottom→top). Each layer has a `palette` mapping each char to one *kind* of thing, and a grid given in one of three ways: `content` (a multi-line grid string), `fill = "x"` (the whole grid filled with one char — e.g. a uniform floor), or `sparse = [{ x, y, ch }, …]` (an all-spaces grid with just those cells set — e.g. a layer of a few objects). To put more than one thing on a cell (e.g. a non-solid object above a wall), put them on different layers — drawing follows layer order.
|
||
|
||
```toml
|
||
# Two terser layer forms, equivalent to a full `content` grid:
|
||
[[boards.room1.layers]]
|
||
fill = "g" # whole layer is grass floor
|
||
palette = { "g" = { kind = "floor", generator = "grass" } }
|
||
|
||
[[boards.room1.layers]]
|
||
sparse = [ { x = 5, y = 3, ch = "C" }, { x = 9, y = 7, ch = "C" } ] # two chests
|
||
palette = { "C" = { kind = "object", script_name = "chest" } } # spaces are implicitly empty
|
||
```
|
||
|
||
```toml
|
||
[world]
|
||
name = "My World"
|
||
start = "room1" # key of the starting board
|
||
|
||
# Named Rhai scripts — shared across all boards. Objects reference a script
|
||
# by script_name = "key". Scripts do NOT live on individual boards.
|
||
[scripts]
|
||
greeter = """
|
||
fn init() { # optional, run once at startup
|
||
log(`player at ${Board.player_x}, ${Board.player_y}`);
|
||
set_tile(2); # write: change my glyph
|
||
}
|
||
fn tick(dt) {
|
||
if Queue.length() == 0 && !blocked(North) { move(North); }
|
||
}
|
||
fn bump(id) { log(`bumped by ${id}`); say("Ouch!"); }
|
||
"""
|
||
|
||
# Each board is a named subtable under [boards]. The board key ("room1") is
|
||
# used for cross-board references (e.g. portals) and becomes current_board_name.
|
||
# NOTE: there is no `player_start` — the player is placed by a kind="player" char.
|
||
[boards.room1.map]
|
||
name = "Room One"
|
||
width = 60
|
||
height = 25
|
||
|
||
# Layer 0 (bottom): the visual floor. Generators roll a fresh textured glyph per
|
||
# cell; a fixed-glyph form (tile/fg/bg, no generator) is also allowed.
|
||
[[boards.room1.layers]]
|
||
content = """
|
||
...60×25 grid of 'g'/'d'...
|
||
"""
|
||
[boards.room1.layers.palette]
|
||
"g" = { kind = "floor", generator = "grass" } # "grass" | "dirt" | "stone"
|
||
"d" = { kind = "floor", generator = "dirt" }
|
||
"." = { kind = "floor", tile = ".", fg = "#222", bg = "#000" } # fixed floor glyph
|
||
|
||
# Layer 1: terrain, the player, objects and portals. A space is always a
|
||
# transparent empty cell, so the floor below shows through.
|
||
[[boards.room1.layers]]
|
||
content = """
|
||
############################################################
|
||
# G @ 1 #
|
||
############################################################
|
||
"""
|
||
[boards.room1.layers.palette]
|
||
# A space is always a transparent empty cell — it is never a palette key.
|
||
"#" = { kind = "wall", tile = 35, fg = "#808080", bg = "#606060" }
|
||
"o" = { kind = "crate", tile = 254, fg = "#aaaaaa", bg = "#000000" } # solid + pushable (any dir)
|
||
"-" = { kind = "hcrate" } # pushable east/west only
|
||
"|" = { kind = "vcrate" } # pushable north/south only
|
||
">" = { kind = "pusher_east" }
|
||
"@" = { kind = "player" } # exactly one across all layers
|
||
# An object: spawned once per occurrence of its char (uppercase by convention).
|
||
# If it has a `name`, only the first instance keeps it (names are board-unique).
|
||
"G" = { kind = "object", tile = "#", fg = "#aa3333", bg = "#000000",
|
||
solid = false, name = "greeter", script_name = "greeter" }
|
||
# A portal: its char must appear exactly once.
|
||
"1" = { kind = "portal", name = "east_door", target_map = "room2", target_entry = "west_door" }
|
||
```
|
||
|
||
Palette `kind` values: the meta-kinds `empty` / `floor` / `object` / `portal` / `player`, or any **archetype name** directly (`wall`, `crate`, `hcrate`, `vcrate`, `pusher_north|south|east|west`). For archetype/floor/object kinds, `tile`/`fg`/`bg` are optional and fall back to that kind's default glyph. An unknown `kind` becomes a visible `ErrorBlock` (logged). A floor entry uses `generator` for a procedural texture or `tile`/`fg`/`bg` for a fixed glyph.
|
||
|
||
Colors are `"#RRGGBB"` hex strings. The player is placed by a `kind = "player"` char, which must appear **exactly once** across all layers (missing → `(0,0)` + error; multiple → first + error); that cell is transparent. `tile` accepts a single-character string (`tile = " "`) or an integer (`tile = 35`). Each layer's `content` multi-line string has its leading newline trimmed by TOML and must match `width × height` (the only hard error); the `fill`/`sparse` forms are always exactly sized. An unknown `kind` produces an `ErrorBlock` and a logged warning. An object is spawned once per occurrence of its char (uppercase by convention) in reading order. **Loading is best-effort and nonfatal** (only a layer grid-dimension mismatch is a hard error): each problem is recorded on `Board` (see `is_valid()` / `load_errors()`). The **player wins its cell**: it silently clears solid terrain under it (on any layer) and drops any conflicting solid object. Script source lives in the world-level `[scripts]` table; objects reference a script by `script_name`. Scripts may define optional `init()`, `tick(dt)`, and `bump(id)` functions; they **read** the world through `Board.*` (e.g. `Board.player_x`), check `blocked(dir) -> bool`, inspect/empty their pending actions via `Queue.length()`/`Queue.clear()`, and **write** via host functions `move(dir)`, `set_tile(n)`, `log(s)`, `say(s)`, and `scroll(lines)`. Writes don't take effect immediately: each is queued and **at most one `move` resolves per 250 ms** per object. When two objects move into the same cell, **lowest id wins** and the bumped object receives `bump(id)`.
|
||
|
||
**Script state across board transitions**: Rhai `Scope` local variables reset when the `ScriptHost` is rebuilt on board entry. Board-side state (object positions, tags, glyph) is preserved because all boards are held as `Rc<RefCell<Board>>` in `World::boards`. Scripts that need to persist information across transitions should encode it in board data (e.g. `set_tag(Me.id, "visited", true)`).
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### Key design decisions
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- **`Behavior` and `Archetype` are separate types** — `Archetype` is the named class of a thing (`Wall`, `Empty`, `Object`); `Behavior` is its runtime properties (`solid`, `opaque`, `pushable`). Adding a new property means adding a field to `Behavior`, not a match arm at every call site.
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- **Draw order is layer order** — `Board::glyph_at` walks `Board::layers` top-down and returns the first thing that draws (a solid object always; a visible non-solid object; a portal; a solid terrain cell; a non-transparent terrain cell). There is no separate floor field: a "floor" is an `Empty` cell with a visible glyph on a lower layer, so a non-solid object on a higher layer can render *above* a solid one. A cell vacated by a pushed crate is left transparent (`Glyph::transparent()`, tile 0), revealing the layer beneath with no movement-code changes. See `board.rs` / `layer.rs`.
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- **One solid per cell (across all layers)** — at most one solid entity (the player, a solid terrain archetype on any layer, *or* a solid object) may occupy a cell. The player is a first-class solid: `Board::solid_at` reports `Solid::Player` for the player's cell (checked first), it blocks movers, and it is **pushable in any direction** — a push chain that reaches the player slides the player along (and is rejected if the player has nowhere to go, e.g. against a wall). The map loader enforces the invariant: a second solid stacked on a cell is dropped (recorded as a load error); the player *wins* its cell — its resolved position (including the `(0, 0)` fallback when no `player` char resolves) silently clears any solid terrain under it (any layer) and drops a conflicting object. `Board::solid_at` relies on this invariant.
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- **Each layer is `Vec<(Glyph, Archetype)>`** — every cell owns its visual and behavioral class directly; there is no per-board element palette or integer indirection. `Archetype` is `Copy` so this is efficient. A transparent cell (glyph tile 0) draws nothing; solidity is read from the archetype regardless of transparency.
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- **Archetypes are referenced by name in map files** — so `ALL_ARCHETYPES` can be reordered or extended without breaking saved games. Adding a variant: the `match`es in `behavior()`/`name()`/`default_glyph()` are exhaustive (the compiler flags them), but **`TryFrom<&str>` and `ALL_ARCHETYPES` are not** — forget the `TryFrom` arm and the archetype silently loads as `ErrorBlock`. Also update the map-format example.
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- **`Board` is the complete unit** — grid, player, objects, and portals all live on `Board`, matching how ZZT treats a "board". No separate wrapper struct.
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- **Glyph (visual) and Archetype (behavior) are decoupled** — each cell has its own `Glyph` (so colors can vary per-cell, e.g. fire flickering) while sharing an `Archetype` with other cells of the same type.
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- **World loading happens in `main()`** before the terminal is initialized, so load errors print to a normal screen and board dimensions are known before the game loop starts.
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### Future direction: the player may become an object
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The long-term goal is for the "player" to be a board *object* that happens to respond to arrow-key events — not a hardcoded special entity — and for some boards to have **no** player at all (a cutscene/menu/puzzle that handles input differently). ZZT hardcoded the player as a special element and authors had to hack around it; avoiding that is deliberate.
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Today's baked-in assumptions that will need to change (don't make `Board.player` *more* central in the meantime — e.g. don't add methods that assume player presence):
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- `Board.player: Player` is required and non-optional; a player-less board can't be represented (should become `Option<Player>`, or move the player out of `Board` to the engine layer).
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- A `kind = "player"` cell is effectively required (exactly one); player spawning should eventually move into the object/script system rather than being a special palette kind.
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- `GameState::try_move` mutates `board.player` directly; once the player is script-driven, movement should go through event dispatch (e.g. `dispatch_event(ArrowKey(dir))`) rather than a dedicated method.
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- The player is rendered as a hardcoded overlay (`Glyph::player()`); it should become part of the normal object layer.
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### Other not-yet-implemented threads
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- **Scripting growth** — more event hooks beyond `init`/`tick`/`bump` (e.g. `on_touch` when the player steps onto an object), a larger action/read vocabulary (more actions could carry a `time_cost`), and persisting script-local state across ticks (needs `call_fn_raw` so the per-object `Scope` isn't rewound each call).
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- **Runtime spawn/destroy of objects** — objects now have stable `ObjectId`s (`Board::objects` is a `BTreeMap<ObjectId, ObjectDef>` with a `next_object_id` counter; `add_object` allocates), so references survive reordering. What's still missing: a `remove_object`, and wiring live spawn/destroy into the `ScriptHost` (it builds one `ObjectRuntime` per object once in `GameState::new`, so an object added after that has no script runtime until the host is rebuilt).
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- **Portals & multi-board** — **done**: `world::load` loads all boards as `Rc<RefCell<Board>>`, `GameState` owns the whole `World` and tracks `current_board_name`. `try_move` detects stepping onto a portal and calls `GameState::enter_board(target_map, target_entry)`, which switches `current_board_name`, places the player at the named arrival portal, clears per-board transient state (speech/scroll), rebuilds the `ScriptHost` for the new board, re-runs `init()`, and sets `board_transition` as a hook. kiln-tui detects the board change in `try_move_with_transition` and plays the `TransitionAnimation` wipe. (Errors — missing target board or entry — are logged, not fatal.)
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- **Load-error surfacing** — `Board::load_errors()` is collected but no front-end displays it yet (kiln-tui could append it to the in-game log at startup).
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