Very interesting concept! I love the visual style and the music. Also, when you reach a checkpoint, I noticed that a new "instrument" is added to the music. Very good detail.
I couldn't reach the end because I got stuck by a bug when I reached the part where there is a moving platform, and you have to hit the enemies, but I fell off, and I was spawned where there's no ground, so now I'm falling for the eternity!
Furthermore, I had some problems with the movement and the wall jump. Sometimes the character gets stuck and can't move consistently. The wall jump is hard to perform, I didn't understand it at all.