Wow! I think this is just the best game jam game I've ever played!
The only thing I miss is a settings-menu. So that you can adjust the volume.
But besides that it looks like you could throw this game as it is on steam and people would buy it. One more: I would change the jump to the [spacebar]. I'm playing on a german keyboard and the [z] and [y] keys are swapped. Fornutately your game is smart enough to notice that. While the UI shows [z] I did jump with [y].
Well - for me it wouldn't be a suprise if you win this jam. Because you really did an awesome job and the game would deserve it!