Nice game, very good idea. just a couple of things:
The game does not have a perfect fit with the theme, it is saved only by the changing of player dimensions. music should not reset everytime you restart the level. Finally in my very personal opinion keys should not be counted as "fuel to jump" nothing wrong with your take, i just find it adds a bit of usless complexity, having to check for the order of the objects taken that, most of the times, is a bit random.
Other than this, the game's scope is perfectly sized for a jam, the artstyle is a bit simple but it works, the gameplay idea is also very good, extra points for the originality! 💯
Overall: good, straight to the point and interesting entry; well done! 👍