Nice little game. It's been ages since I played a Sokoban type game. I didn't find any bugs with your mechanic and the levels were nice and straightforward. I remember playing the original Sokoban on MSDOS and it got VERY hard very quickly.
(I think there was a bug with the level select, after I won the game I wanted to go back to the main menu but pressing the X button it seemed to hang or exit?)