Congrats on finishing the jam!
I like infinite runners. I found the pressing down to increase downward momentum a little clunky. Maybe make it so the longer you hold jump the higher you go, then it increases gravity when you release the button?
Also, those jumps where you have to jump and then slide midair feel super unintuitive. People don't actually slide in the air, and while that doesn't matter since this is a video game, it does make realizing what you're supposed to do/instinctively knowing at speed unintuitive
Level design wise, you may want to write an algorithm to ensure you aren't spawning impossible layouts instead of just straight randomization. I had a few cases that were absolutely impossible to dodge
The art for this game is really nice looking. Only thing I would note is I struggled sometimes separating the foreground from the background. Had several cases where I crashed because I didn't realize something was an obstacle. I would recommend making the color choices for the foreground markedly distinct from the background, either by using a different color entirely or by using a substantial value/saturation gap
The music was pretty good!
Oh yeah, one more thing: the ui. Just a quick note, if I navigate your menus with the mouse, don't make me swap to the keyboard for some interactions and vice versa. I should be able to only use one input method for the whole thing. (Your credits requires you to push escape to exit it, which the rest of the UI doesn't do)
Honestly, I'm finding it pretty remarkable how polished this prototype is given how little time there was to make it. Your overall presentation is really solid. You could easily clean up the rough edges on this game and have something that feels complete
Good luck to you on your future games!