builtin macro

CLAUDE.md

@@ -140,7 +140,7 @@ Colors are `"#RRGGBB"` hex strings. The player is placed by a `kind = "player"`
 - **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`.
 - **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.
 - **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.
-- **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.
+- **Archetypes are referenced by name in map files** — so variants can be reordered or extended without breaking saved games. **Terrain archetypes** (`Wall`, `Crate`, etc.): the `match`es in `behavior()`/`name()`/`default_glyph()` are exhaustive (the compiler flags them), but `TryFrom<&str>` is not — forget its arm and the new name silently loads as `ErrorBlock`. **Script-backed archetypes** (`Builtin`): adding one requires only (1) an entry in the `builtins!` macro invocation in `archetype.rs` and (2) the `.rhai` script file — `TryFrom<&str>`, `behavior()`, `name()`, `default_glyph()`, and the expansion pass all derive from the macro output automatically. In both cases, also update the map-format example.
 - **`Board` is the complete unit** — grid, player, objects, and portals all live on `Board`, matching how ZZT treats a "board". No separate wrapper struct.
 - **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.
 - **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.