I quite liked it! It's a good concept for a puzzle platformer, and there's a lot of room to explore the mechanic further, I feel. (If not only for Game Jam limitations.)
I adore dynamic soundtracks, so the two versions of the level theme was great. Given the "dream" theme and the way the versions sounded, it gave me Mario & Luigi Dream Team vibes.
My biggest suggestion, taking into account that this is a game jam game so many limitations apply, is that I would've loved a variable jump height. Meaning that the longer/shorter you hold the jump button, the higher/lower you go. The high jump height and low gravity make sense given some of the puzzles. (Would be unnecessarily hard to switch modes in midair if the gravity if didn't jump as high and fell faster.) But needing to jump full height to clear 1 or 2 block heights feels a little cumbersome, for example.
I really liked it overall, though. And it feels like a great use of the theme!