I loved the ramp up in difficulty, great tutorialisation of mechanics! Level 9 had me stumped for a long time, and I liked how it turned from a platformer into a puzzle game. Great job but I hated how much you hurt my brain.
One tiny criticism is that some jumps are a bit fiddly. I would probably add space to jump as well as add in a bit of coyote time (see Mark's great video on platforming)