The fact that you managed to create and publish a complete title, with an intro, story, menu, cool art, music and sounds, and thoughtful level design in a game jam is super impressive! I like the coin / level select mechanic in particular.
If you plan on working on the game after the jam, I’d recommend experimenting with precise platform movement. In general, “slippery” physics will work better in tempo-heavy platformers, but this is more of a single-screen precision experience, which benefits greatly from tight controls. There are also some collision issues that, while perfectly understandable for a jam game, would definitely have to be corrected in a more polished rendition as they break the gameplay momentum. As one final nitpick, I would add arrow key movement controls, as some platformer players will simply not play a game without that layout. Congrats!