Thanks a lot! Glad you like the concept, I also do hope there's still a decent bit of design space left to explore :) (and even if I would manage to exhaust what is possible with the current set of elements, I believe there's definitely still room to explore interactions with a lot of other platforming tropes that are not in the game yet)
Gladly writing down all of the feedback, this is my first proper try at making a platformer and the controls definitely still need a decent bit of work. And yeah, level 5 is becoming more and more clear as one I'll have to axe -- I made it as a theme and variation level, but the more I look at it, the more it seems like only one of the variations is actually interesting.