Wow this really surprised me! it was already a really solid platformer from the get go, but then you just kept adding more and more content. I'm amazed at the scope of art and music you were able to do for the jam, great work!
I only have one big piece of feedback about the game. I think if you put some work into the camera it would really help the feel of the game. The biggest issue with the camera right now is it's placement. The fact that you can't see almost anything below you makes a lot of jumps blind, causing some unnecessary frustration. I also think a little camera smoothing would go a long way for the game feel.
Otherwise great entry that was super enjoyable! You should be very proud of your first game :) Keep up the good work!