Too simple...
I'm all up for puzzles and such, but when it's too easy, it gets too boring. Try to spice things up a bit. Put in some enemies. Make the levels bigger, and more challenging. Some explosions would be cool, too.
It's a nice game, and runs real well, but it just gets too boring, too quick, is all. Make this game more challenging, and I'm sure this game can be one of the best!