private void setLevels() {
    tilesToDrop.clear();
    for (int deletedRow : deletedRows) {
      for (int row = deletedRow-1; row >= 0; row --) {
        for (int col = 0; col < Game.WIDTH; col++){
          Tile tile = tiles[col][row];
          if(tile.isNotEmpty()){
            if(tile.level == 0)
              tilesToDrop.add(tile);
            tile.level++;
          }
        }
      }
    }
  }