Amazing job with the level design! I liked how you would come across areas where you'd have to remember to come back to later once you got more jumps. The small hitboxes and the sliding corners on platform edges were nice touches in addition to the smooth controls! The art and music were fitting too!
I managed to beat the game after about a dozen deaths haha. I was going to suggest a checkpoint, but after reading Fredspipa's feedback below, I appreciate your level design even more. There was really only one ledge near the end that I found really difficult, so maybe if that area was closer to the starting point, that would make dying there less punishing.
Overall, awesome platformer!