Brilliant. This is an excellent puzzle game with a unique twist. Mechanically, everything is done well. The sound effects are nice, the music is relaxing. The graphics are simple, but the shine effects are cool. You've also added the polish missing in a lot of these games: a mute button, level restart, move undo button (a lot of programmers forget about his), level select, home/main menu. And when you beat all the levels, you do give us a nice message with some fireworks.
If there's anything I could advise you on, it's just that the game needs a slightly better tutorial. On the first level, it took me a minute to figure out exactly what was going on and how the game worked. Subsequent levels do explain further elements, though experimentation is the key to figuring out the concepts. Also, I found the movement to be a little frustrating; grabbing a tile with the mouse was easy, but I found that sometimes I accidentally moved too far and pushed other tiles out of place, sometimes making a level unwinnable. Still, the very useful undo button made this manageable.
I also found the game pretty easy. Only one level toward the middle gave me trouble. The game is more of a casual play. Thankfully, that's what I was looking for.
I'd love to see some more levels of this, maybe some new mechanics. Really cool idea. Keep up the good work, and keep bringing us games of such quality.