var NUM_COLS = 5;
var NUM_ROWS = 4;
for (var i = 0; i < NUM_COLS; i++) {
  for (var j = 0; j < NUM_ROWS; j++) {
    var tileX = i * 54 + 5;
    var tileY = j * 54 + 40;
    tiles.push(new Tile(tileX, tileY));
  }
}