made grab simpler

kiln-core/CLAUDE.md

@@ -27,7 +27,7 @@ The core types that were formerly monolithic in `game.rs` are now split into foc
 
 **`kiln-core/src/utils.rs`** — shared primitive types (`pub(crate)`):
 - `Pushable` (`No`/`Any`/`Horizontal`/`Vertical`) — which directions a solid may be pushed. `allows(dir) -> bool`.
-- `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).
+- `Behavior` — plain data struct from `Archetype::behavior()`: `solid: bool`, `opaque: bool`, `pushable: Pushable`, `grab: bool` (the player walking onto a `solid + grab` thing isn't blocked — it moves onto it and the thing's `grab()` hook fires; this is the *only* grab trigger, and only `Gem` sets the flag).
 - `ObjectId = u32` — stable identifier for board objects.
 - `Solid` — the single solid occupant of a cell, returned by `Board::solid_at`: `Player`, `Cell(Archetype)`, or `Object(ObjectId)`.
 - `Player { x: i32, y: i32 }` — current player position.
@@ -49,11 +49,11 @@ The core types that were formerly monolithic in `game.rs` are now split into foc
 - `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.
+- `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`. The **player** is always a blocker (a shift can't relocate it and `apply_swap` refuses to overwrite it).
 - `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`).
 - `add_object(obj) -> ObjectId`, `remove_object(id) -> Option<ObjectDef>`, `object_ids_at(x, y)`, `solid_object_id_at(x, y)` — object add/remove + queries.
-- `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.)
+- `grab_object_at(x, y) -> Option<ObjectId>` — a solid `grab` object on the cell (the player-walks-onto-it case). `GameState::try_move` uses it to fire `grab()` instead of bumping when the player steps onto a grab thing. Grab is **only** a player-movement event: a grab thing pushed/swapped into the player is treated as an ordinary solid (no special-case). (`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.
+- `apply_swap(pairs: &[(i32,i32,i32,i32)]) -> Vec<LogLine>` — 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 is no exception: it is refused like any other solid). Because a refused solid stays at its source cell, which another entry may also target, a final **overlap sweep** over the swapped cells keeps one solid per cell 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).
 - `in_bounds((i32, i32))` — bounds-checks a possibly-negative coord.
@@ -63,7 +63,7 @@ The core types that were formerly monolithic in `game.rs` are now split into foc
 - `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.
+- `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). **`try_move` is the only grab trigger** — a grab thing pushed or swapped into the player is an ordinary solid (it slides/blocks/refuses like any other). `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)`). 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).
@@ -80,7 +80,7 @@ The core types that were formerly monolithic in `game.rs` are now split into foc
 
 **`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: the key is the object's `script_name` (a world-pool name for a named script, or a synthetic `BUILTIN_*` name assigned by `expand_builtin_archetypes` so identical built-ins, e.g. all pushers, share one AST); the source is the pool entry for that name, or the object's embedded `builtin_script` when present. 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.
+- 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 a `grab` thing — the only grab trigger), 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`).

kiln-core/src/board.rs

@@ -4,31 +4,10 @@ use crate::layer::Layer;
 use crate::log::LogLine;
 use crate::object_def::ObjectDef;
 use crate::utils::Direction;
-use crate::utils::{ObjectId, Player, PortalDef, RegistryValue, Solid};
+use crate::utils::{Behavior, ObjectId, Player, PortalDef, Pushable, RegistryValue, Solid};
 use std::collections::{BTreeMap, HashMap, HashSet};
 use crate::builtin_scripts::archetype_script_key;
 
-/// A captured solid occupant of a cell, used by [`Board::apply_swap`] to read
-/// every source cell before writing any destination (so cyclic moves work).
-#[derive(Clone)]
-enum SolidSnapshot {
-    /// The player occupied the cell.
-    Player,
-    /// A solid scripted object occupied the cell, identified by its stable id.
-    Object(ObjectId),
-    /// A solid terrain cell — its visual/behavior plus the layer it lived on.
-    Terrain {
-        /// Layer the terrain lived on (restored on the destination).
-        z: usize,
-        /// The cell's glyph.
-        glyph: Glyph,
-        /// The cell's archetype.
-        arch: Archetype,
-    },
-    /// No solid occupant.
-    Empty,
-}
-
 /// The complete state of one game board (a single room or screen).
 ///
 /// `Board` is the central data structure of the engine, equivalent to a
@@ -208,15 +187,28 @@ impl Board {
     pub fn solid_at(&self, x: usize, y: usize) -> Option<Solid> {
         // The player wins its cell (load-time invariant), so it is the solid there.
         if self.player.x == x as i32 && self.player.y == y as i32 {
-            return Some(Solid::Player);
+            return Some(Solid::player_at(x, y));
         }
-        // A solid object shadows the cell it sits on.
+        // A solid object shadows the cell it sits on; capture its behavior now.
         if let Some(id) = self.solid_object_id_at(x, y) {
-            return Some(Solid::Object(id));
+            let obj = &self.objects[&id];
+            let behavior = Behavior {
+                solid: obj.solid,
+                opaque: obj.opaque,
+                // ObjectDef stores pushability as a bool meaning "any direction".
+                pushable: if obj.pushable {
+                    Pushable::Any
+                } else {
+                    Pushable::No
+                },
+                grab: obj.grab,
+            };
+            return Some(Solid::object_at(x, y, id, behavior));
         }
         // Otherwise some layer's terrain archetype may be solid (e.g. a wall).
         if let Some(z) = self.solid_cell_layer(x, y) {
-            return Some(Solid::Cell(self.get(z, x, y).1));
+            let (glyph, arch) = *self.get(z, x, y);
+            return Some(Solid::terrain_at(x, y, z, glyph, arch));
         }
         None
     }
@@ -260,8 +252,7 @@ impl Board {
         let solid2 = solid2.unwrap();
 
         // This is probably disallowed then, but let's check for a player coexisting with a grab:
-        if solid1.player() && solid2.grab(self) ||
+        if solid1.player() && solid2.grab() || solid2.player() && solid1.grab() {
-            solid2.player() && solid1.grab(self) {
             return true
         }
 
@@ -275,12 +266,10 @@ impl Board {
     /// Grid archetypes may restrict the axis (see [`Pushable`]); pushable objects
     /// can be shoved in any direction.
     fn is_pushable(&self, x: usize, y: usize, dir: Direction) -> bool {
-        match self.solid_at(x, y) {
+        // The captured `pushable` is `Any` for the player and a pushable object,
-            Some(Solid::Player) => true, // the player is pushable in any direction
+        // axis-constrained for directional crates, `No` otherwise.
-            Some(Solid::Cell(a)) => a.behavior().pushable.allows(dir),
+        self.solid_at(x, y)
-            Some(Solid::Object(id)) => self.objects[&id].pushable,
+            .is_some_and(|s| s.pushable().allows(dir))
-            None => false,
-        }
     }
 
     /// Whether the chain of pushable solids starting at `(x, y)` can be shoved one
@@ -323,11 +312,9 @@ impl Board {
     /// another pushable that is itself moving the same frame. Returns `false` if
     /// `(x, y)` holds no pushable, or the cell ahead runs off the board.
     ///
-    /// Shifting onto the **player** is allowed only when the source is a
+    /// The **player** is always a blocker: a shift can't relocate the player, and
-    /// [`grab`](crate::object_def::ObjectDef::grab) thing: it isn't shoving the
+    /// `apply_swap` refuses to overwrite it, so a cell holding the player is never
-    /// player aside (a shift can't relocate the player, and `apply_swap` would
+    /// an acceptable shift destination.
-    /// refuse to overwrite it), it's being grabbed — the player stays put and the
-    /// thing despawns. Any other solid treats the player as a blocker.
     pub fn can_shift(&self, x: usize, y: usize, dir: Direction) -> bool {
         // The source must hold a solid pushable in `dir`.
         if !self.is_pushable(x, y, dir) {
@@ -339,10 +326,11 @@ impl Board {
             return false; // nothing to shift into off the board
         }
         let (nx, ny) = (next.0 as usize, next.1 as usize);
-        // Shifting onto the player is only legitimate for a grab thing (it gets
+        // The player always blocks a shift: a shift can't relocate it and
-        // grabbed, the player isn't moved); otherwise the player is a blocker.
+        // `apply_swap` refuses to overwrite it. (The player reads as pushable, so it
-        if matches!(self.solid_at(nx, ny), Some(Solid::Player)) {
+        // must be excluded explicitly before the cell-ahead test below.)
-            return self.grab_object_at(x, y).is_some();
+        if self.solid_at(nx, ny).is_some_and(|s| s.player()) {
+            return false;
         }
         // The cell ahead is acceptable if it is empty or another pushable solid.
         self.is_passable(nx, ny) || self.is_pushable(nx, ny, dir)
@@ -381,19 +369,16 @@ impl Board {
     /// The caller guarantees the destination is already clear.
     fn shift_solid(&mut self, x: usize, y: usize, dx: i32, dy: i32) {
         let (tx, ty) = ((x as i32 + dx) as usize, (y as i32 + dy) as usize);
-        // The player owns its cell, so move it before considering objects/terrain.
+        let Some(solid) = self.solid_at(x, y) else {
-        if self.player.x == x as i32 && self.player.y == y as i32 {
+            return; // nothing to shift
-            self.player.x = tx as i32;
+        };
-            self.player.y = ty as i32;
+        // A terrain cell leaves a transparent cell behind (revealing any floor); the
-        } else if let Some(id) = self.solid_object_id_at(x, y) {
+        // player and objects carry no grid cell, so there is nothing to vacate. `place`
-            let obj = self.objects.get_mut(&id).expect("id from object_id_at");
+        // captured the glyph/arch, so clearing the source first is safe.
-            obj.x = tx;
+        if let Some(z) = self.solid_cell_layer(x, y) {
-            obj.y = ty;
-        } else if let Some(z) = self.solid_cell_layer(x, y) {
-            let moved = *self.get(z, x, y);
-            *self.get_mut(z, tx, ty) = moved;
             *self.get_mut(z, x, y) = (Glyph::transparent(), Archetype::Empty);
         }
+        solid.place(self, tx, ty);
     }
 
     /// Returns the [`ObjectId`]s of the objects at `(x, y)`, if any.
@@ -431,35 +416,6 @@ impl Board {
         })
     }
 
-    /// Returns the [`ObjectId`] of a **grab** object that a push at `(x, y)` in
-    /// `dir` would shove into the player, if any.
-    ///
-    /// Walks the pushable chain from `(x, y)`; if a chain cell holds a grab object
-    /// whose immediate forward neighbour is the player, that object is returned.
-    /// This is the "grab thing pushed into the player" case: rather than sliding
-    /// the player along, the caller grabs the thing (see
-    /// [`GameState`](crate::game::GameState)). Returns `None` for an ordinary push.
-    pub fn pushed_grab_into_player(&self, x: usize, y: usize, dir: Direction) -> Option<ObjectId> {
-        let (dx, dy): (i32, i32) = dir.into();
-        let (mut cx, mut cy) = (x, y);
-        // Advance through the contiguous run of pushable solids.
-        while self.is_pushable(cx, cy, dir) {
-            let next = (cx as i32 + dx, cy as i32 + dy);
-            if !self.in_bounds(next) {
-                return None;
-            }
-            let (nx, ny) = (next.0 as usize, next.1 as usize);
-            // If the next cell is the player and this cell is a grab object, the
-            // push would drive that grab thing into the player: grab it instead.
-            if matches!(self.solid_at(nx, ny), Some(Solid::Player)) {
-                return self.grab_object_at(cx, cy);
-            }
-            cx = nx;
-            cy = ny;
-        }
-        None
-    }
-
     /// Inserts `object`, assigning it the next free [`ObjectId`], and returns that id.
     ///
     /// Ids start at 1 and increase monotonically; an id is never reused, so it
@@ -585,20 +541,12 @@ impl Board {
     /// a write that would overwrite the player without relocating it is skipped and
     /// logged (the player wins its cell, per the one-solid-per-cell invariant).
     ///
-    /// **Grab:** a [`grab`](crate::object_def::ObjectDef::grab) object whose
+    /// A solid refused onto the player is left at its source cell, which another
-    /// destination is the player isn't written onto the player — it is left where it
+    /// entry may also target; a final sweep over the swapped cells resolves any
-    /// is and its id is returned in the second tuple element so the caller can fire
+    /// such **overlap** — it keeps one solid, deletes the rest (never the player),
-    /// its `grab()` hook (it gets grabbed, the player isn't moved). Because a
+    /// and logs an error per deletion.
-    /// grabbed object stays put (and its `grab()` may not despawn it), it can end up
+    pub fn apply_swap(&mut self, pairs: &[(i32, i32, i32, i32)]) -> Vec<LogLine> {
-    /// sharing a cell with a solid that moved in; a final sweep over the swapped
-    /// cells resolves any such **overlap** — it keeps one solid (preferring a
-    /// grabbed object so its `grab()` can still fire), deletes the rest (never the
-    /// player), and logs an error per deletion.
-    pub fn apply_swap(&mut self, pairs: &[(i32, i32, i32, i32)]) -> (Vec<LogLine>, Vec<ObjectId>) {
         let mut errors = Vec::new();
-        // Grab objects whose destination was the player: left in place here, their
-        // grab() hooks fired by the caller (GameState).
-        let mut grabbed: Vec<ObjectId> = Vec::new();
 
         // 1. Validate: keep only entries whose source and destination are in bounds.
         let mut valid: Vec<((i32, i32), (i32, i32))> = Vec::new();
@@ -613,26 +561,27 @@ impl Board {
         }
 
         // 2. Snapshot the solid at each unique source (read phase). Reading every
-        //    source before any write is what lets cycles/swaps resolve.
+        //    source before any write is what lets cycles/swaps resolve. `None` is an
-        let mut snapshots: HashMap<(i32, i32), SolidSnapshot> = HashMap::new();
+        //    empty source (the old `SolidSnapshot::Empty`).
+        let mut snapshots: HashMap<(i32, i32), Option<Solid>> = HashMap::new();
         for &(src, _) in &valid {
-            snapshots
+            snapshots.entry(src).or_insert_with(|| {
-                .entry(src)
+                self.solid_at(src.0 as usize, src.1 as usize)
-                .or_insert_with(|| self.snapshot_solid(src));
+            });
         }
 
         // 3. Compute the final occupant of every affected cell. A source that is not
-        //    anyone's destination is vacated (Empty); each entry writes its source's
+        //    anyone's destination is vacated (None); each entry writes its source's
         //    snapshot into its destination (a later entry wins a repeated destination).
         let dsts: HashSet<(i32, i32)> = valid.iter().map(|&(_, d)| d).collect();
-        let mut final_state: HashMap<(i32, i32), SolidSnapshot> = HashMap::new();
+        let mut final_state: HashMap<(i32, i32), Option<Solid>> = HashMap::new();
         for &(src, _) in &valid {
             if !dsts.contains(&src) {
-                final_state.insert(src, SolidSnapshot::Empty);
+                final_state.insert(src, None);
             }
         }
         for &(src, dst) in &valid {
-            final_state.insert(dst, snapshots[&src].clone());
+            final_state.insert(dst, snapshots[&src]);
         }
 
         // The player's final cell: where a Player snapshot is installed, else its
@@ -640,7 +589,7 @@ impl Board {
         // overwritten — computed up front so it's stable across the write loop.
         let player_final = final_state
             .iter()
-            .find(|(_, s)| matches!(s, SolidSnapshot::Player))
+            .find(|(_, s)| s.is_some_and(|s| s.player()))
             .map(|(&c, _)| c)
             .unwrap_or((self.player.x, self.player.y));
 
@@ -649,10 +598,7 @@ impl Board {
         //     objects keep their entity and are repositioned by the install step.
         let survivors: HashSet<ObjectId> = final_state
             .values()
-            .filter_map(|s| match s {
+            .filter_map(|s| s.and_then(|s| s.object_id()))
-                SolidSnapshot::Object(id) => Some(*id),
-                _ => None,
-            })
             .collect();
         let affected: HashSet<(i32, i32)> = snapshots
             .keys()
@@ -662,10 +608,10 @@ impl Board {
         for &(cx, cy) in &affected {
             let (ux, uy) = (cx as usize, cy as usize);
             match self.solid_at(ux, uy) {
-                Some(Solid::Object(id)) if !survivors.contains(&id) => {
+                Some(s) if s.object_id().is_some_and(|id| !survivors.contains(&id)) => {
-                    self.remove_object(id);
+                    self.remove_object(s.object_id().unwrap());
                 }
-                Some(Solid::Cell(_)) => {
+                Some(s) if s.archetype().is_some() => {
                     if let Some(z) = self.solid_cell_layer(ux, uy) {
                         *self.get_mut(z, ux, uy) = (Glyph::transparent(), Archetype::Empty);
                     }
@@ -677,58 +623,36 @@ impl Board {
         // 4b. Install each cell's computed occupant.
         for (&(cx, cy), snap) in &final_state {
             let (ux, uy) = (cx as usize, cy as usize);
+            // Empty cells were already cleared in phase 4a.
+            let Some(solid) = snap else { continue };
             // The player wins its cell: never overwrite player_final with anything
-            // other than the player itself.
+            // other than the player itself. A refused solid stays at its source
-            if (cx, cy) == player_final && !matches!(snap, SolidSnapshot::Player) {
+            // cell; the overlap sweep below cleans up if that cell is now also
-                // A grab object shoved onto the player is grabbed, not blocked: leave
+            // someone else's destination.
-                // it where it is (don't install onto the player) and report it so the
+            if (cx, cy) == player_final && !solid.player() {
-                // caller fires its grab() hook. The overlap sweep below cleans up if
-                // its source cell is now also someone else's destination.
-                if let SolidSnapshot::Object(id) = snap
-                    && self.objects.get(id).is_some_and(|o| o.grab)
-                {
-                    grabbed.push(*id);
-                    continue;
-                }
                 errors.push(LogLine::error(format!(
                     "swap: cannot overwrite the player at ({cx},{cy})"
                 )));
                 continue;
             }
-            match snap {
+            solid.place(self, ux, uy);
-                SolidSnapshot::Empty => {} // already cleared
-                SolidSnapshot::Terrain { z, glyph, arch } => {
-                    *self.get_mut(*z, ux, uy) = (*glyph, *arch);
-                }
-                SolidSnapshot::Object(id) => {
-                    if let Some(obj) = self.objects.get_mut(id) {
-                        obj.x = ux;
-                        obj.y = uy;
-                    }
-                }
-                SolidSnapshot::Player => {
-                    self.player.x = cx;
-                    self.player.y = cy;
-                }
-            }
         }
 
-        // 5. Overlap sweep: a grabbed object left in place (above) may now share a
+        // 5. Overlap sweep: a solid refused onto the player (above) stays at its
-        //    cell with a solid that moved in. For any swapped cell holding more than
+        //    source cell, which may now also be a destination another entry wrote
-        //    one solid, keep a single occupant — a grabbed object if present (so its
+        //    into. For any swapped cell holding more than one solid, keep a single
-        //    grab() can still fire), otherwise whatever remains — and delete the rest
+        //    occupant and delete the rest (never the player). Logs an error per
-        //    (never the player). Logs an error per deletion.
+        //    deletion.
         for &(cx, cy) in &affected {
             let (ux, uy) = (cx as usize, cy as usize);
             let player_here = self.player.x == cx && self.player.y == cy;
-            // Solid objects on this cell, with grabbed ones first so we keep one.
+            // Solid objects on this cell; keep the first, delete the rest.
-            let mut objs: Vec<ObjectId> = self
+            let objs: Vec<ObjectId> = self
                 .objects
                 .iter()
                 .filter(|(_, o)| o.x == ux && o.y == uy && o.solid)
                 .map(|(&id, _)| id)
                 .collect();
-            objs.sort_by_key(|id| !grabbed.contains(id));
             let has_terrain = self.solid_cell_layer(ux, uy).is_some();
 
             // How many solids share the cell (player + solid objects + solid terrain).
@@ -740,9 +664,9 @@ impl Board {
                 "swap: {total} solids overlap at ({cx},{cy}); deleting extras"
             )));
 
-            // Pick the survivor (priority: player > grabbed/first object > terrain)
+            // Pick the survivor (priority: player > first object > terrain) and
-            // and delete every other solid. The player is only ever a survivor, so
+            // delete every other solid. The player is only ever a survivor, so it
-            // it is never deleted. `keep_obj` is the object we keep, if any.
+            // is never deleted. `keep_obj` is the object we keep, if any.
             let keep_obj = (!player_here).then(|| objs.first().copied()).flatten();
             for id in &objs {
                 if Some(*id) != keep_obj {
@@ -758,28 +682,7 @@ impl Board {
             }
         }
 
-        (errors, grabbed)
+        errors
-    }
-
-    /// Reads the solid occupant of `(x, y)` into a [`SolidSnapshot`] (for
-    /// [`apply_swap`](Board::apply_swap)). Coordinates must be in bounds.
-    fn snapshot_solid(&self, (x, y): (i32, i32)) -> SolidSnapshot {
-        let (ux, uy) = (x as usize, y as usize);
-        match self.solid_at(ux, uy) {
-            Some(Solid::Player) => SolidSnapshot::Player,
-            Some(Solid::Object(id)) => SolidSnapshot::Object(id),
-            Some(Solid::Cell(arch)) => {
-                let z = self
-                    .solid_cell_layer(ux, uy)
-                    .expect("a solid terrain cell has a layer");
-                SolidSnapshot::Terrain {
-                    z,
-                    glyph: self.get(z, ux, uy).0,
-                    arch,
-                }
-            }
-            None => SolidSnapshot::Empty,
-        }
     }
 
     /// Returns the index of the layer whose terrain cell at `(x, y)` is non-`Empty`
@@ -798,7 +701,7 @@ pub(crate) mod tests {
     use crate::layer::Layer;
     use crate::object_def::ObjectDef;
     use crate::utils::Direction;
-    use crate::utils::{ObjectId, Player, Solid};
+    use crate::utils::{ObjectId, Player};
     use color::Rgba8;
     use std::collections::{BTreeMap, HashMap};
 
@@ -888,23 +791,18 @@ pub(crate) mod tests {
         assert!(board.solid_at(0, 0).is_none());
         assert!(board.is_passable(0, 0));
 
-        match board.solid_at(1, 0) {
+        let wall = board.solid_at(1, 0).expect("a wall is solid");
-            Some(Solid::Cell(Archetype::Wall)) => {}
+        assert_eq!(wall.archetype(), Some(Archetype::Wall));
-            other => panic!("expected Solid::Cell(Wall), got {:?}", other.is_some()),
-        }
         assert!(!board.is_passable(1, 0));
 
-        match board.solid_at(2, 0) {
+        let obj = board.solid_at(2, 0).expect("an object is solid");
-            Some(Solid::Object(id)) => {
+        let id = obj.object_id().expect("expected a solid object");
-                assert_eq!((board.objects[&id].x, board.objects[&id].y), (2, 0))
+        assert_eq!((board.objects[&id].x, board.objects[&id].y), (2, 0));
-            }
-            _ => panic!("expected Solid::Object"),
-        }
         assert!(!board.is_passable(2, 0));
     }
 
     #[test]
-    fn grab_helpers_detect_a_gem() {
+    fn grab_object_at_detects_a_gem() {
         // A grabbable gem object at (1,0); the player at (2,0).
         let mut gem = ObjectDef::new(1, 0);
         gem.grab = true;
@@ -914,14 +812,6 @@ pub(crate) mod tests {
         // grab_object_at finds the gem on its own cell, nowhere else.
         assert_eq!(board.grab_object_at(1, 0), Some(1));
         assert_eq!(board.grab_object_at(0, 0), None);
-
-        // Pushing the gem east shoves it into the player → reported as a grab.
-        assert_eq!(
-            board.pushed_grab_into_player(1, 0, Direction::East),
-            Some(1)
-        );
-        // Pushing it west (away from the player) is an ordinary push.
-        assert_eq!(board.pushed_grab_into_player(1, 0, Direction::West), None);
     }
 
     #[test]
@@ -936,10 +826,10 @@ pub(crate) mod tests {
     #[test]
     fn solid_at_reports_player() {
         let board = open_board(3, 1, (1, 0), vec![]);
-        match board.solid_at(1, 0) {
+        assert!(
-            Some(Solid::Player) => {}
+            board.solid_at(1, 0).is_some_and(|s| s.player()),
-            _ => panic!("expected Solid::Player at the player's cell"),
+            "expected the player at its own cell"
-        }
+        );
         assert!(!board.is_passable(1, 0));
     }
 
@@ -1001,16 +891,16 @@ pub(crate) mod tests {
     }
 
     #[test]
-    fn can_shift_into_player_only_for_a_grab_thing() {
+    fn can_shift_treats_the_player_as_a_blocker() {
-        // A grab gem at (0,0) may shift east onto the player at (1,0): it gets
+        // The player is always a blocker for a shift — even a grab gem may not shift
-        // grabbed rather than blocked.
+        // onto it (grab now fires only on player movement, not on being shifted in).
         let mut gem = ObjectDef::new(0, 0);
         gem.grab = true;
         gem.pushable = true;
         let board = open_board(2, 1, (1, 0), vec![gem]);
-        assert!(board.can_shift(0, 0, Direction::East));
+        assert!(!board.can_shift(0, 0, Direction::East));
 
-        // A plain crate may not shift onto the player — the player blocks it.
+        // A plain crate likewise may not shift onto the player.
         let mut board = open_board(2, 1, (1, 0), vec![]);
         crate_at(&mut board, 0, 0);
         assert!(!board.can_shift(0, 0, Direction::East));
@@ -1192,7 +1082,7 @@ pub(crate) mod tests {
         let mut board = open_board(3, 1, (1, 0), vec![]);
         crate_at(&mut board, 0, 0);
         wall_at(&mut board, 2, 0);
-        let (errs, _) = board.apply_swap(&[(0, 0, 2, 0), (2, 0, 0, 0)]);
+        let errs = board.apply_swap(&[(0, 0, 2, 0), (2, 0, 0, 0)]);
         assert!(errs.is_empty());
         assert_eq!(board.get(0, 0, 0).1, Archetype::Wall);
         assert_eq!(board.get(0, 2, 0).1, Archetype::Crate);
@@ -1206,7 +1096,7 @@ pub(crate) mod tests {
         // a = (0,0) empty, b = (1,0) crate, c = (2,0) wall.
         crate_at(&mut board, 1, 0);
         wall_at(&mut board, 2, 0);
-        let (errs, _) = board.apply_swap(&[(0, 0, 1, 0), (1, 0, 2, 0)]);
+        let errs = board.apply_swap(&[(0, 0, 1, 0), (1, 0, 2, 0)]);
         assert!(errs.is_empty());
         assert_eq!(board.get(0, 0, 0).1, Archetype::Empty);
         assert_eq!(board.get(0, 1, 0).1, Archetype::Empty);
@@ -1217,7 +1107,7 @@ pub(crate) mod tests {
     fn apply_swap_empty_onto_object_removes_it() {
         // Moving an empty source onto an object despawns the object.
         let mut board = open_board(3, 1, (2, 0), vec![ObjectDef::new(1, 0)]);
-        let (errs, _) = board.apply_swap(&[(0, 0, 1, 0)]);
+        let errs = board.apply_swap(&[(0, 0, 1, 0)]);
         assert!(errs.is_empty());
         assert!(board.solid_object_id_at(1, 0).is_none());
         assert!(board.objects.is_empty());
@@ -1229,7 +1119,7 @@ pub(crate) mod tests {
         let mut board = open_board(3, 1, (2, 0), vec![]);
         crate_at(&mut board, 0, 0);
         wall_at(&mut board, 1, 0);
-        let (errs, _) = board.apply_swap(&[(0, 0, 1, 0)]);
+        let errs = board.apply_swap(&[(0, 0, 1, 0)]);
         assert!(errs.is_empty());
         assert_eq!(board.get(0, 0, 0).1, Archetype::Empty);
         assert_eq!(board.get(0, 1, 0).1, Archetype::Crate);
@@ -1239,7 +1129,7 @@ pub(crate) mod tests {
     fn apply_swap_moves_object_and_player() {
         // An object and the player relocate (swap places) in one batch.
         let mut board = open_board(3, 1, (0, 0), vec![ObjectDef::new(2, 0)]);
-        let (errs, _) = board.apply_swap(&[(0, 0, 2, 0), (2, 0, 0, 0)]);
+        let errs = board.apply_swap(&[(0, 0, 2, 0), (2, 0, 0, 0)]);
         assert!(errs.is_empty());
         assert_eq!((board.player.x, board.player.y), (2, 0));
         assert_eq!((board.objects[&1].x, board.objects[&1].y), (0, 0));
@@ -1249,7 +1139,7 @@ pub(crate) mod tests {
     fn apply_swap_out_of_bounds_skips_and_logs() {
         let mut board = open_board(3, 1, (2, 0), vec![]);
         crate_at(&mut board, 0, 0);
-        let (errs, _) = board.apply_swap(&[(0, 0, 9, 0)]);
+        let errs = board.apply_swap(&[(0, 0, 9, 0)]);
         assert_eq!(errs.len(), 1);
         assert_eq!(board.get(0, 0, 0).1, Archetype::Crate); // unchanged
     }
@@ -1259,41 +1149,37 @@ pub(crate) mod tests {
         // A crate moved onto the (non-relocating) player is rejected and logged.
         let mut board = open_board(3, 1, (1, 0), vec![]);
         crate_at(&mut board, 0, 0);
-        let (errs, _) = board.apply_swap(&[(0, 0, 1, 0)]);
+        let errs = board.apply_swap(&[(0, 0, 1, 0)]);
         assert_eq!(errs.len(), 1);
         assert_eq!((board.player.x, board.player.y), (1, 0)); // player kept its cell
         assert_eq!(board.get(0, 0, 0).1, Archetype::Empty); // source still vacated
     }
 
     #[test]
-    fn apply_swap_grab_onto_player_is_reported_not_moved() {
+    fn apply_swap_grab_onto_player_is_refused_like_any_solid() {
-        // A grab gem swapped onto the player is reported (for its grab() hook) and
+        // A grab gem swapped onto the player is no longer special: it is refused and
-        // left at its source rather than overwriting / sliding the player.
+        // logged (the player wins its cell), and left at its source. Grab fires only
+        // when the player walks onto a grab thing, not when one is swapped in.
         let mut gem = ObjectDef::new(0, 0);
         gem.grab = true;
         gem.pushable = true;
         let mut board = open_board(2, 1, (1, 0), vec![gem]);
-        let (errs, grabbed) = board.apply_swap(&[(0, 0, 1, 0)]);
+        let errs = board.apply_swap(&[(0, 0, 1, 0)]);
-        assert!(errs.is_empty());
+        assert_eq!(errs.len(), 1); // refusal logged
-        assert_eq!(grabbed, vec![1]);
         assert_eq!((board.player.x, board.player.y), (1, 0)); // player kept its cell
         assert_eq!((board.objects[&1].x, board.objects[&1].y), (0, 0)); // gem stayed
     }
 
     #[test]
-    fn apply_swap_overlap_after_grab_deletes_the_other_solid() {
+    fn apply_swap_overlap_after_refused_player_write_deletes_the_other_solid() {
-        // gem (0,0)→player (1,0) [grabbed, stays at (0,0)] while a crate (2,0)→(0,0)
+        // object (0,0)→player (1,0) [refused, stays at (0,0)] while a crate (2,0)→(0,0)
-        // moves into the gem's cell. The sweep keeps the grabbed gem and deletes the
+        // moves into the object's cell. The sweep keeps the object and deletes the
-        // crate, logging the overlap.
+        // crate; one error logs the refusal, one logs the overlap.
-        let mut gem = ObjectDef::new(0, 0);
+        let mut board = open_board(3, 1, (1, 0), vec![ObjectDef::new(0, 0)]);
-        gem.grab = true;
-        gem.pushable = true;
-        let mut board = open_board(3, 1, (1, 0), vec![gem]);
         crate_at(&mut board, 2, 0);
-        let (errs, grabbed) = board.apply_swap(&[(0, 0, 1, 0), (2, 0, 0, 0)]);
+        let errs = board.apply_swap(&[(0, 0, 1, 0), (2, 0, 0, 0)]);
-        assert_eq!(grabbed, vec![1]);
+        assert_eq!(errs.len(), 2); // the refusal and the overlap were logged
-        assert_eq!(errs.len(), 1); // the overlap was logged
+        assert_eq!((board.objects[&1].x, board.objects[&1].y), (0, 0)); // object kept
-        assert_eq!((board.objects[&1].x, board.objects[&1].y), (0, 0)); // gem kept
         assert_eq!(board.get(0, 0, 0).1, Archetype::Empty); // crate deleted
         assert_eq!((board.player.x, board.player.y), (1, 0)); // player untouched
     }

kiln-core/src/game.rs

@@ -2,7 +2,7 @@ use crate::action::Action;
 use crate::board::Board;
 use crate::log::LogLine;
 use crate::script::ScriptHost;
-use crate::utils::{Direction, ObjectId, Player, ScriptArg, Solid};
+use crate::utils::{Direction, ObjectId, Player, ScriptArg};
 use crate::world::World;
 use std::cell::{Ref, RefMut};
 use std::time::Duration;
@@ -210,9 +210,6 @@ impl GameState {
         // below also borrows `self`.
         let mut logs: Vec<LogLine> = Vec::new();
         let mut bumps: Vec<(ObjectId, i64)> = Vec::new();
-        // Grab hooks to fire (player walked into / pushed a grab thing); fired after
-        // the board borrow drops, like bumps.
-        let mut grabs: Vec<ObjectId> = Vec::new();
         // Net change to the player's gem count from AddGems actions; applied to
         // `self` after the board borrow drops.
         let mut gem_delta: i64 = 0;
@@ -225,13 +222,9 @@ impl GameState {
             for ba in actions {
                 match ba.action {
                     Action::Move(dir) => {
-                        let outcome = step_object(&mut board, ba.source, dir);
+                        if let Some(bumped) = step_object(&mut board, ba.source, dir) {
-                        if let Some(bumped) = outcome.bumped {
                             bumps.push((bumped, ba.source as i64));
                         }
-                        if let Some(grabbed) = outcome.grabbed {
-                            grabs.push(grabbed);
-                        }
                     }
                     Action::SetTile(tile) => {
                         if let Some(obj) = board.objects.get_mut(&ba.source) {
@@ -311,23 +304,14 @@ impl GameState {
                     Action::Push { x, y, dir } => {
                         if !board.in_bounds((x, y)) {
                             logs.push(LogLine::error(format!("push({x},{y}): out of bounds")));
-                        } else if let Some(grabbed) =
-                            board.pushed_grab_into_player(x as usize, y as usize, dir)
-                        {
-                            // A grab thing shoved into the player is grabbed, not pushed.
-                            grabs.push(grabbed);
                         } else {
                             board.push(x as usize, y as usize, dir);
                         }
                     }
                     // apply_swap reads all sources then writes all destinations, so a
                     // whole batch of moves resolves simultaneously (cycles included).
-                    // A grab thing swapped onto the player is reported back for its
-                    // grab() hook (fired in phase B with the other grabs).
                     Action::Swap(pairs) => {
-                        let (errs, grabbed) = board.apply_swap(&pairs);
+                        logs.extend(board.apply_swap(&pairs));
-                        logs.extend(errs);
-                        grabs.extend(grabbed);
                     }
                     // Accumulated and applied to `self.player_gems` after the borrow drops.
                     Action::AddGems(n) => gem_delta += n,
@@ -355,11 +339,6 @@ impl GameState {
         for (bumped, bumper) in bumps {
             self.scripts.run_bump(bumped, bumper);
         }
-        // Fire grab() hooks (player walked into / pushed a grab thing). The hook
-        // typically adds a stat and calls die(); those actions resolve next pass.
-        for grabbed in grabs {
-            self.scripts.run_grab(grabbed);
-        }
         for (target, fn_name, arg) in sends {
             self.scripts.run_send(target, &fn_name, arg);
         }
@@ -454,10 +433,10 @@ impl GameState {
             grabbed = board.grab_object_at(nx, ny);
             // A solid object in the way is bumped by the player (id -1) — but a
             // grab thing fires grab() instead of bump(), so don't also bump it.
-            bumped = match board.solid_at(nx, ny) {
+            bumped = board
-                Some(Solid::Object(_)) if grabbed.is_none() => board.solid_object_id_at(nx, ny),
+                .solid_at(nx, ny)
-                _ => None,
+                .filter(|_| grabbed.is_none())
-            };
+                .and_then(|s| s.object_id());
             if grabbed.is_some() || board.is_passable(nx, ny) || board.can_push(nx, ny, dir) {
                 // Don't push a grab thing aside — walk onto it. Otherwise shove any
                 // pushable chain out of the way (no-op when there's nothing to push).
@@ -494,61 +473,31 @@ impl GameState {
     }
 }
 
-/// The side effects of a [`step_object`] call that the caller resolves after the
+/// Moves object `id` one cell in `dir` on `board`, returning the object it bumped
-/// board borrow drops: a `bump`ed object and/or a `grab`bed object.
+/// (if any) for the caller to resolve after the board borrow drops.
-#[derive(Default)]
-struct StepOutcome {
-    /// A solid object the mover collided with (target cell was occupied by it).
-    bumped: Option<ObjectId>,
-    /// A grab object the move shoved into the player (its `grab()` hook should fire).
-    grabbed: Option<ObjectId>,
-}
-
-/// Moves object `id` one cell in `dir` on `board`, returning the objects it bumped
-/// and/or grabbed (see [`StepOutcome`]).
 ///
 /// The move itself proceeds only if the target is in bounds and either passable or a
 /// pushable solid the object can shove out of the way (see [`Board::can_push`]). The
 /// bump is recorded whenever a solid object occupies the target — whether it gets
 /// pushed aside or blocks the move — since something tried to move into it. Walls and
 /// crates carry no script, so only solid objects yield a bump.
-///
+fn step_object(board: &mut Board, id: ObjectId, dir: Direction) -> Option<ObjectId> {
-/// If the push would shove a **grab** thing into the player (see
-/// [`Board::pushed_grab_into_player`]), the push is skipped and the grab thing is
-/// reported instead of sliding the player along.
-fn step_object(board: &mut Board, id: ObjectId, dir: Direction) -> StepOutcome {
     let (dx, dy): (i32, i32) = dir.into();
-    let Some((ox, oy)) = board.objects.get(&id).map(|o| (o.x, o.y)) else {
+    let (ox, oy) = board.objects.get(&id).map(|o| (o.x, o.y))?;
-        return StepOutcome::default();
-    };
     let target = (ox as i32 + dx, oy as i32 + dy);
     if !board.in_bounds(target) {
-        return StepOutcome::default();
+        return None;
     }
     let (nx, ny) = (target.0 as usize, target.1 as usize);
-    // A push that would drive a grab thing into the player grabs it instead of
-    // sliding the player; skip the move entirely (the grab thing despawns itself).
-    if let Some(grabbed) = board.pushed_grab_into_player(nx, ny, dir) {
-        return StepOutcome {
-            bumped: None,
-            grabbed: Some(grabbed),
-        };
-    }
     // Capture the bumped object before any push relocates it (its id is stable).
-    let bumped = match board.solid_at(nx, ny) {
+    let bumped = board.solid_at(nx, ny).and_then(|s| s.object_id());
-        Some(Solid::Object(_)) => board.solid_object_id_at(nx, ny),
-        _ => None,
-    };
     if board.is_passable(nx, ny) || board.can_push(nx, ny, dir) {
         board.push(nx, ny, dir); // shoves a crate/object out of the way; no-op otherwise
         let obj = board.objects.get_mut(&id).expect("id checked above");
         obj.x = nx;
         obj.y = ny;
     }
-    StepOutcome {
+    bumped
-        bumped,
-        grabbed: None,
-    }
 }
 
 #[cfg(test)]
@@ -580,9 +529,11 @@ mod tests {
     }
 
     #[test]
-    fn pushing_a_gem_into_the_player_grabs_it() {
+    fn pushing_a_gem_into_the_player_does_not_grab() {
-        // A non-solid script object at (0,0) pushes the gem at (1,0) east into the
+        // A non-solid script object at (0,0) pushes the gem at (1,0) east toward the
-        // player at (2,0); the gem is grabbed rather than sliding the player.
+        // player at (2,0). Grab now fires only on player movement, so the gem is an
+        // ordinary solid here: the chain can't move (the player is backed against
+        // the board edge), so nothing happens and the gem is not collected.
         let mut sobj = ObjectDef::new(0, 0);
         sobj.solid = false;
         sobj.script_name = Some("s".to_string());
@@ -596,41 +547,12 @@ mod tests {
         let mut game = GameState::with_scripts(board, scripts);
         game.run_init();
 
-        // First tick: the push resolves into a grab (gem's grab() is queued).
-        // Second tick: the gem's add_gems()/die() resolve.
         game.tick(Duration::from_millis(16));
         game.tick(Duration::from_millis(16));
 
-        assert_eq!(game.player_gems, 1);
+        // No grab: the gem is untouched and the player never moved.
-        // The gem (the only non-script object) is gone; the player never moved.
+        assert_eq!(game.player_gems, 0);
-        assert!(!game.board().objects.values().any(|o| o.grab));
+        assert!(game.board().objects.values().any(|o| o.grab));
-        assert_eq!((game.board().player.x, game.board().player.y), (2, 0));
-    }
-
-    #[test]
-    fn swapping_a_gem_into_the_player_grabs_it() {
-        // A non-solid script object swaps the gem at (1,0) onto the player at (2,0).
-        // apply_swap reports the grab; the gem's grab() collects it and die()s.
-        let mut sobj = ObjectDef::new(0, 0);
-        sobj.solid = false;
-        sobj.script_name = Some("s".to_string());
-        let mut board = open_board(3, 1, (2, 0), vec![sobj]);
-        stamp(&mut board, 1, 0, Archetype::Gem);
-        board.expand_builtin_archetypes();
-        let scripts = HashMap::from([(
-            "s".to_string(),
-            "fn tick(dt) { if Queue.length() == 0 { swap([[1, 0, 2, 0]]); } }".to_string(),
-        )]);
-        let mut game = GameState::with_scripts(board, scripts);
-        game.run_init();
-
-        // First tick: the swap reports the grab (gem's grab() is queued).
-        // Second tick: the gem's add_gems()/die() resolve.
-        game.tick(Duration::from_millis(16));
-        game.tick(Duration::from_millis(16));
-
-        assert_eq!(game.player_gems, 1);
-        assert!(!game.board().objects.values().any(|o| o.grab));
         assert_eq!((game.board().player.x, game.board().player.y), (2, 0));
     }
 

kiln-core/src/utils.rs

@@ -68,35 +68,165 @@ pub struct Behavior {
 /// objects were reordered/destroyed.
 pub type ObjectId = u32;
 
-/// The single solid occupant of a board cell, returned by [`Board::solid_at`].
+/// Which kind of thing a [`Solid`] is, plus the data needed to relocate it.
+///
+/// Private to [`Solid`]: callers ask through the [`Solid`] accessors
+/// ([`Solid::player`], [`Solid::object_id`], [`Solid::archetype`]) rather than
+/// matching the kind directly.
+#[derive(Copy, Clone)]
+enum SolidKind {
+    /// The player occupies the cell. The player carries no grid cell of its own.
+    Player,
+    /// A solid scripted object, identified by its stable [`ObjectId`].
+    Object(ObjectId),
+    /// A solid terrain cell, with everything needed to rewrite it elsewhere.
+    Terrain {
+        /// Layer the terrain lives on.
+        z: usize,
+        /// The cell's glyph.
+        glyph: Glyph,
+        /// The cell's archetype.
+        arch: Archetype,
+    },
+}
+
+/// The single solid occupant of a board cell, captured from a `&Board` at given
+/// coordinates by [`Board::solid_at`].
 ///
 /// At most one solid — the player, a grid [`Archetype`], *or* an [`ObjectDef`] — may
 /// occupy a cell (the invariant enforced at load time), so this represents the one
-/// thing a mover would collide with there.
+/// thing a mover would collide with there. Absence of a solid is `None`, not a
-pub enum Solid {
+/// variant of this type.
-    /// The player occupies the cell. The player is solid (it blocks movers) and
+///
-    /// pushable in any direction (see [`Board::is_pushable`]).
+/// `Solid` is `Copy`: it captures its occupant's coordinates, behavior, and (for
-    Player,
+/// terrain) the glyph/archetype/layer needed to relocate it *at construction time*,
-    /// The cell's grid archetype is itself solid (e.g. [`Archetype::Wall`]).
+/// so movement logic can answer behavior questions and [`place`](Solid::place) the
-    Cell(Archetype),
+/// occupant elsewhere without re-borrowing the board. This is what lets
-    /// A solid [`ObjectId`] occupies the cell.
+/// [`Board::apply_swap`] read every source before writing any destination.
-    Object(ObjectId),
+#[derive(Copy, Clone)]
+pub struct Solid {
+    /// Column the occupant was read from.
+    x: usize,
+    /// Row the occupant was read from.
+    y: usize,
+    /// What kind of occupant this is (and its relocation data).
+    kind: SolidKind,
+    /// The occupant's behavior, captured at creation: the player's is synthesized
+    /// (solid + opaque + pushable any direction + not grabbable), terrain reads
+    /// [`Archetype::behavior`], an object's is built from its `solid`/`opaque`/
+    /// `pushable`/`grab` flags.
+    behavior: Behavior,
 }
 
 impl Solid {
+    /// Builds the player solid at `(x, y)`.
+    pub(crate) fn player_at(x: usize, y: usize) -> Solid {
+        Solid {
+            x,
+            y,
+            kind: SolidKind::Player,
+            // The player is solid + opaque, pushable in any direction, never grabbable.
+            behavior: Behavior {
+                solid: true,
+                opaque: true,
+                pushable: Pushable::Any,
+                grab: false,
+            },
+        }
+    }
+
+    /// Builds a solid object at `(x, y)` from its [`ObjectDef`]-derived flags.
+    pub(crate) fn object_at(x: usize, y: usize, id: ObjectId, behavior: Behavior) -> Solid {
+        Solid {
+            x,
+            y,
+            kind: SolidKind::Object(id),
+            behavior,
+        }
+    }
+
+    /// Builds a solid terrain cell at `(x, y)` on layer `z`.
+    pub(crate) fn terrain_at(x: usize, y: usize, z: usize, glyph: Glyph, arch: Archetype) -> Solid {
+        Solid {
+            x,
+            y,
+            kind: SolidKind::Terrain { z, glyph, arch },
+            behavior: arch.behavior(),
+        }
+    }
+
+    /// The coordinates the occupant was read from.
+    pub fn coords(&self) -> (usize, usize) {
+        (self.x, self.y)
+    }
+
     /// Whether this occupant is the player.
     pub fn player(&self) -> bool {
-        matches!(self, Solid::Player)
+        matches!(self.kind, SolidKind::Player)
+    }
+
+    /// The occupant's [`ObjectId`], if it is a scripted object.
+    pub fn object_id(&self) -> Option<ObjectId> {
+        match self.kind {
+            SolidKind::Object(id) => Some(id),
+            _ => None,
+        }
+    }
+
+    /// The occupant's terrain archetype, if it is a terrain cell.
+    pub fn archetype(&self) -> Option<Archetype> {
+        match self.kind {
+            SolidKind::Terrain { arch, .. } => Some(arch),
+            _ => None,
+        }
+    }
+
+    /// Which directions the occupant may be pushed (the player → [`Pushable::Any`]).
+    pub fn pushable(&self) -> Pushable {
+        self.behavior.pushable
     }
 
     /// Whether this occupant is a **grab** thing (a gem-like solid the player
-    /// collects on contact). The player itself is never grabbable; a terrain cell
+    /// collects on contact). The player is never grabbable.
-    /// reports its archetype's `grab` flag, and an object reports its own.
+    pub fn grab(&self) -> bool {
-    pub fn grab(&self, board: &Board) -> bool {
+        self.behavior.grab
-        match self {
+    }
-            Solid::Player => false,
+
-            Solid::Cell(arch) => arch.behavior().grab,
+    /// Whether this occupant blocks movement (always true for a `Solid`).
-            Solid::Object(id) => board.objects.get(id).is_some_and(|obj| obj.grab),
+    pub fn solid(&self) -> bool {
+        self.behavior.solid
+    }
+
+    /// Whether this occupant blocks line of sight.
+    pub fn opaque(&self) -> bool {
+        self.behavior.opaque
+    }
+
+    /// Writes this occupant into the cell at `(x, y)`, relocating it there.
+    ///
+    /// Writes the **destination only** — it does *not* vacate the occupant's
+    /// original cell. Callers that need the source cleared (e.g.
+    /// [`Board::shift_solid`]) do so separately; [`Board::apply_swap`] relies on
+    /// this by clearing all sources in a dedicated phase before installing
+    /// destinations, so cyclic moves and swaps resolve correctly.
+    ///
+    /// The player moves via [`Board::player`]; an object updates its
+    /// [`ObjectDef`] position; a terrain cell rewrites `(glyph, arch)` at `(x, y)`.
+    pub fn place(self, board: &mut Board, x: usize, y: usize) {
+        match self.kind {
+            SolidKind::Player => {
+                board.player.x = x as i32;
+                board.player.y = y as i32;
+            }
+            SolidKind::Object(id) => {
+                if let Some(obj) = board.objects.get_mut(&id) {
+                    obj.x = x;
+                    obj.y = y;
+                }
+            }
+            SolidKind::Terrain { z, glyph, arch } => {
+                *board.get_mut(z, x, y) = (glyph, arch);
+            }
         }
     }
 }