constructor(cols, rows, tilewidth, tileheight) {
		this.cols = cols;
		this.rows = rows;
		this.tilewidth = tilewidth;
		this.tileheight = tileheight;
		this.bounds = new Bounds();
	}
@param {number} cols - width of the tilemap in tiles
@param {number} rows - height of the tilemap in tiles
@param {number} tilewidth - width of each tile in pixels
@param {number} tileheight - height of each tile in pixels