v0.6: Actor system (rigidbody) replaces pixel player

- New actors.rs: Rigidbody Actor with gravity, grid collision, powder displacement
- Actor rendered as colored rectangle on pixel buffer (zoom-scaled)
- WASM API: spawn_actor, move_actor, update_actor, actor_x/y
- WASD/Arrow keys control actor, camera follows with soft lerp
- displace_powders pushes sand/dirt out of actor area
- Collision: stops at solids, walks through powders
- Updated AGENTS.md with actor documentation

web/src/engine.ts

@@ -8,6 +8,11 @@ import __wbg_init, {
   render_buffer_len,
   render_width,
   render_height,
+  spawn_actor,
+  actor_x,
+  actor_y,
+  move_actor,
+  update_actor,
 } from "../pkg/atomic_engine.js";
 
 export const M = {
@@ -79,6 +84,11 @@ export interface Engine {
   renderBufferLen: () => number;
   renderWidth: () => number;
   renderHeight: () => number;
+  spawnActor: (x: number, y: number) => void;
+  actorX: () => number;
+  actorY: () => number;
+  moveActor: (dx: number, dy: number) => void;
+  updateActor: (dt: number) => void;
   memory: WebAssembly.Memory;
 }
 
@@ -96,5 +106,10 @@ export async function createEngine(gridWidth: number, gridHeight: number): Promi
     renderWidth: () => render_width(),
     renderHeight: () => render_height(),
     memory: wasm.memory,
+    spawnActor: (x, y) => spawn_actor(x, y),
+    actorX: () => actor_x(),
+    actorY: () => actor_y(),
+    moveActor: (dx, dy) => move_actor(dx, dy),
+    updateActor: (dt) => update_actor(dt),
   };
 }

web/src/main.ts

@@ -99,9 +99,9 @@ async function main() {
     }
   }
 
-  // === Spawn point: center on the castle ===
+  engine.spawnActor(400, 550);
   camera.x = 400;
-  camera.y = 630;
+  camera.y = 550;
 
   const rw = engine.renderWidth();
   const rh = engine.renderHeight();
@@ -184,11 +184,21 @@ async function main() {
       );
     }
 
-    const speed = 200;
-    if (input.isDown("KeyA") || input.isDown("ArrowLeft")) camera.x -= speed * dt;
-    if (input.isDown("KeyD") || input.isDown("ArrowRight")) camera.x += speed * dt;
-    if (input.isDown("KeyW") || input.isDown("ArrowUp")) camera.y -= speed * dt;
-    if (input.isDown("KeyS") || input.isDown("ArrowDown")) camera.y += speed * dt;
+    let mx = 0;
+    let my = 0;
+    if (input.isDown("KeyA") || input.isDown("ArrowLeft")) mx = -1;
+    if (input.isDown("KeyD") || input.isDown("ArrowRight")) mx = 1;
+    if (input.isDown("KeyW") || input.isDown("ArrowUp")) my = -1;
+    engine.moveActor(mx, my);
+    engine.updateActor(dt);
+
+    const ax = engine.actorX();
+    const ay = engine.actorY();
+    if (ax > 0 || ay > 0) {
+      camera.x += (ax - camera.x) * 10 * dt;
+      camera.y += (ay - 60 - camera.y) * 10 * dt;
+    }
+
     if (input.isDown("Equal")) camera.setZoom(camera.zoom + 2 * dt);
     if (input.isDown("Minus")) camera.setZoom(camera.zoom - 2 * dt);
     if (input.wheel !== 0) {