Amazing game. The level design is huge, I can see a lot of effort put into that. The gameplay is quite basic but the addition of new mechanics is fun and makes the game more interesting. Plus the animation is awesome so it's even more enjoyable to dash and climb. Did you code all these controls from scratch during the jam? It's very impressive to get all of them working and creating a challenge in a such a big level in just two days.
The graphics are very nice even though I would prefer more diversity across the huge level to make it more interesting and memorable. But if I add animation, it's amazing work done in 48 hours.
The soundtrack was my favorite, really liked the instrumental music (especially that pizzicato!). Changing it with every new mechanic discovery is a nice touch. It would be even more memorable and epic if the music became more intense with every change. But overall, the sound really fits with the graphics and the story creating a great intense mood. Again, really impressive for such a short period of time!
Finally, when it comes to game design, I think it's a bit too tough. You were very kind to include the checkpoint feature but it played an evil trick on me at the place where the note is in a dead-end and you need to do a lot of wall-jumps to get out. After about 30 tries to get out of there and get to another challenging note I gave up. But I'm dying to know whether there are more new mechanics after that. It's great that you posted the ending in a reply below, so at least I know how it finished. Great story-telling by the way!
Sorry for a lot of text. Just wanted to share some impressions and ideas. TLDR: amazing job on all fronts, really enjoyed it!