Such a well designed and executed game. Nice job! I really like the way that the game slowly present each new mechanic to the player. It such a good polishing touch that make the whole play through much smoother and pleasant.
I can't think of anything on top of my head that urgently needs improvement. I guess the only complaint I had was the game ending too soon, and would hope it to be longer. The game do have potential to be developed into a full game though.
Anyway, Well done!