Nice work, I like the art style and atmospherics (the level completion animation is great, e.g.). The game unfolded in an intuitive way, which is great, and I played it to the finish. It took me a bit to realize that pushing jump twice very rapidly was the most effective.
On the third level, on the left-hand side, there were a few times when my player was on a platform and suddenly could no longer jump, and the walk animation no longer played (I could only slide back and forth). I'm not sure what caused it, but each time it was after attempting several jumps.
I hope that's helpful feedback! Nice job!