anchor.diff:             (type == TileType.CLOSED_DOOR);
     }
   
  -  bool get isTransparent() {
  -    return (type == TileType.FLOOR) ||
  -           (type == TileType.LOW_WALL) ||
  -           (type == TileType.OPEN_DOOR);
  -  }
  +  bool get isTransparent() => type.isTransparent;
   }
positive.code: }
  
  class TileType {
    static final FLOOR       = const TileType(0);
    static final WALL        = const TileType(1);
    static final LOW_WALL    = const TileType(2);
    static final OPEN_DOOR   = const TileType(3);
    static final CLOSED_DOOR = const TileType(4);
  
    final int _value;
    const TileType(this._value);
  }
  
  class Tile {
  
negative.code: 
    bool get isExplored() => _explored;
  
    bool get isPassable() => type.isPassable;
  
    bool get isTraversable() {
      return (type == TileType.FLOOR) ||
  