anchor.diff:    int width;
     int height;
   
  -  /// Creates a new tile layer from JSON data
  +  /// Creates a new tile layer from TMX data
     TileLayer(this.layer, this.parent) {
       width = int.parse(layer.getAttribute("width"));
       height = int.parse(layer.getAttribute("height"));
  
positive.code: part of cobblestone;
  
  /// Loads a JSON tilemap from a URL. Use Tiled to create these. (http://www.mapeditor.org/)
  Future<Tilemap> loadTilemap(String url) {
    return HttpRequest
        .getString(url)
  
negative.code:   Map<int, BasicTile> basicTiles;
    Map<int, Tile> tileset;
  
    /// Creates a new tilemap from a TMX map
    Tilemap(this.file) {
      this.width = int.parse(file.rootElement.getAttribute("width"));
      this.height = int.parse(file.rootElement.getAttribute("height"));
  