Aaaaaaannnnd that's a 5/5/5/5/5/5 ! That's a really, really, REALLY good game (please, note that when I say something in uppercase and bold, that's important =p). I love the Celeste-like aspect, with a clever concept that is simple to understand but allows a lot of possibilities (and it perfectly fits the theme too).
The movement is smooth, the game was hard but never unfair, the graphics are on point and the music is really good (the music style you chose isn't what I would have imagined for this game, it has a more a "Mario-Kart" vibe to it, but the quality is undeniable). Maybe you would need to tweak a bit the inertia of the character and the fall speed, but nothing too crazy.
I had a bug where I died and phased at the same time, resulting in a softlock, but since I could R, that was ok , it happens =).
In all seriousness, you have a concept. Like, really. I would love to see a more complete game on Steam, with more levels, mechanics and a story. If you decide to push that idea and release it on Steam, please, ping me, I'll be glad to buy a copy.
Thank you a lot for your game. I really enjoyed these 10-ish minutes of gameplay. It felt like my first minutes of games like Celeste or The Messenger, where I know that I'm playing something special, and it's really rare to feel that in a Game jam.
Keep up the good work !