I liked the game, but I think you could give mroe instructions to player. For example: I took a long time to understand that you cannot jump on crates with a X. I also think the first level is harder than the others, seems progression is inversed. My suggestions: make a better difficulty progression and give more instructions to player. Great idea, really creative game!
If you could, play my game too: https://itch.io/jam/gmtk-2019/rate/460644