tiny refactor of entity code.

js/entity.mjs

@@ -59,7 +59,5 @@ export function move (entity, d_x, d_y) {
 }
 
 function out_of_bounds (entity) {
-	const { x, y } = entity;
-	return x < 0 || x >= BOX_SIZE ||
-		y < 0 || y >= BOX_SIZE
+	return world.out_of_bounds(entity.x, entity.y);
 }