Quite a cool concept ! I'dd suggest adding one intermediary shrinking size, to complexify the game a little bit. Also, some boxes in the level are a bit misaligned, which makes it look a bit wierd. Appart from that, I liked the difficulty ! You could also consider adding some checkpoints (maybe some collectable coins ?) to avoid teleporting back the player right at the begining. I'd also suggest adding a final victory screen and music, for final touches :)
Anyways, good job !