Interesting idea. The mechanic of having an alternate reality that you need to pay attention to is not unique to this game, but so far it was the first time I saw it having more applications than just the visual effects. You actually use it to eliminate hazards and to make platforms fall down. I liked seeing this game in action and the final zone was interesting, albeit a bit depressing. In fact, the whole atmosphere was depressing, but that was the intention so I'm counting that as a positive!
I noticed a bug: There is a solid square that should be in the "real" reality but is not (next to the big ball of spikes).
This game desperately needs checkpoints! It was really annoying going all the way back to the beginning every time I died. Also a bit boring, since I had already seen the first challenges multiple times, and it takes a while to get to the main mechanic of the game. It would also be helpful if you had jumping sound effects at least!
Very interesting how you implemented a character selection in a game jam entry! It's a detail that I don't often see. Overall I enjoyed this game, I just wish you had checkpoints!