Fun puzzle game! I like that the levels slowly teach you how to play the game. The sound effects give some nice feedback, and the levels themselves are good. I enjoyed this game, which is why I was so annoyed at how fickle the dragging is. Sometimes it just won't let you drag the trail to the next square. You can't go back to the previous square, you always have to start from the beginning. Sometimes you can't drag it anywhere. If you would have offered keyboard controls as an alternative, I wouldn't have complained this much. Also some music would be appropriate for this. But the game design is top notch, great job!