public static void leave(int pos) {
   if (Dungeon.level.heaps.get(pos) == null) {
     Level.set(pos, Terrain.DOOR);
     GameScene.updateMap(pos);
     Dungeon.observe();
   }
 }
  public static void enter(int pos) {
    Level.set(pos, Terrain.OPEN_DOOR);
    GameScene.updateMap(pos);
    Dungeon.observe();

    if (Dungeon.visible[pos]) {
      Sample.INSTANCE.play(Assets.SND_OPEN);
    }
  }