This is a really good idea, and you managed to explore it well with some nicely designed levels. It's a really solid main mechanic, and the art and sound design compliment it all nicely. It just needs polishing and bugfixing, then you can extend it with as many levels as you can come up with!
In terms of bugs, aside from the black level bug, I also encountered an instance where the player sprite rotated after being hit with a boulder. This persisted on death and sent me into the ceiling whenever I tried to move forward.
As other people have said the player movment should be touched up a bit. I'd increase the players friction, as I seemed to slide on surfaces long after I stopped pressing the key. I'd also tweak the jump such that the player reaches the apex much quicker to reduce the floaty feeling. You take too long to reach the peak of the jump compared to the much quicker time to hit the floor. I'd also try to reduce the hang time by a tiny bit as well. I'd finally suggest widening whatever it is you're using for floor collisions, I'd often find that hitting space had no effect when trying to take a running jump off a platform.
None of these issues really take away from how fun the main mechanic is though, which definitelyshows its strength.
On a point unrelated to the game though, I wish I could score you on feedback given. I've seen your comments on a lot of games and you seem to be giving the best constructive feedback of anyone participating in the jam. So well done, and a massive thank you from me personally!