Replayability. Play as many times as you want on randomly-generated levels;Size matters! Pick a level size suitable for you: from 3x3 tiles to 12x7;How high can you push it? Get a score for each solved puzzle based on it's difficulty and your efficiency;Two game modes. Normal mode provides a more relaxing experience, since you can swap any two tiles. For a bigger challenge, try Hardcore mode where your turns are