Very cute and polished art/effects/music. The movement feels good too. A couple of notes:
Walking onto a jump pad gives you much better height than jumping on it.
Sliding down slopes has too much friction, even at a decent incline I would come to a halt mid-slide.
Jump-slide allowed me to cheese my way up slopes very easily, don't know if that was intentional or not.
Wall jump detection seemed kinda spotty. I was able to wall jump when I needed to but I never got a "feeling" for how or when it was supposed to happen. Generally if I rubbed my face against the wall during the peak of my double jump it happened. It was less "I'll jump here and then wall jump off this wall and then..." but more "I need to get to that platform so I'll double jump against this wall and just assume my character will cling to it at some point".
It's very easy to cheese my way up the walls like the ones in the second screenshot by chaining jump-jump-walljump-slide. I don't know how intentional this is.
General level design thoughts: I'm assuming the demo level was just the test room but the floating platforms leading up to the top of the tower (first screenshot) was pretty Kaizo compared with the rest of the level. It being a big optional difficulty challenge is fine, but if you mess up and fall down getting back to the platforms was really annoying. The path back was too boring and time consuming compared with the actually interesting platforming challenge at the end. It sunk my motivation for giving it another shot.
Again I really like the art and sound, and it felt good to jump around in! I can't wait to play it again in a more fleshed out level!