add terrain collision

src/entity.js

@@ -28,15 +28,22 @@ export default class Entity {
   set y(value) { this.position.y = value }
 
   get collidables() {
-    return this.game?.entities.filter((e) => e.id != this.id).map((e) => e.collider)
+    const entityColliders = (this.game?.entities ?? []).filter((e) => e.id != this.id).map((e) => e.collider)
+    const terrainColliders = (this.game?.terrains ?? []).map((t) => t.colliders).flat()
+
+    return entityColliders.concat(terrainColliders)
   }
 
   get collider() {
     return new SAT.Circle(new SAT.Vector(this.x, this.y), this.radius)
   }
 
-  isColliding(collider) {
-    return SATX.colliding(this.collider, collider)
+  get colliders() {
+    return [this.collider]
+  }
+
+  isColliding(...colliders) {
+    return SATX.collideObjects(this.collider, colliders)
   }
 
   moveAction(x, y) {
@@ -71,7 +78,7 @@ export default class Entity {
       const position = distance <= speed ? fixedDest : stepTaken
 
       const collider = Entity.collider(position.x, position.y, this.radius)
-      const isColliding = this.collidables.some((c) => SATX.colliding(collider, c))
+      const isColliding = SATX.collideObjects(collider, this.collidables)
 
       if (!isColliding) {
         this.position.copy(position)