For a first solo game jam game, it's really impressive. You avoid a lot of classic mistakes, such as having 3Cs or unpleasant metrics. The game plays well, and the slide is a welcome addition.
I think the thing the game is missing most right now is an input buffer, which would make certain sequences much more enjoyable (I died way too many times on the rock sequence for exemple x)
But it was worth the effort, the boss is very cool and really well animated.
The enemies quickly become obstacles that you try to avoid rather than confront, but if they could give you something, like life for example, it would make them more interesting.
Honestly, it was great fun, although a little too hard. Nice work!