This was incredibly cool! Just a few thoughts:
The music loop is only around 50 seconds, but the levels are several minutes long. It can get kind of grating to hear the music repeated so much.
I also wanted to let you know that I got stuck in this spot-- I had moved the box to the left as far as it would go, and then I could no longer get on top of the box, making it impossible for me to finish the level!
Good luck with the full version!