I really like how the two characters have different functions, and it's not just two squares that can jump. The levels seem well-designed and I like the music and the simplistic graphics.
Most of this game's difficulty comes from fighting the controls, unfortunately. The black box's gravity reverse skill in particular is wildly inconsistent. I don't know if there's a cooldown associate with it, but if there is then there should be a visual indicator. Oftentimes I'd press the up arrow and it wouldn't do anything, which led to several deaths by falling or by spike. The jam hitbox is also really misleading - my character would often come into contact with it visually, but it wouldn't pick it up. This happened so many times on level three that I eventually had to give up.
I played this game on the downloadable version, by the way. I suspect the reason why the controls are so inconsistent is because you have a print statement in one of your update loops, which is overflowing the stack and causing some of the inputs to not register.
When the controls did work though, I had a lot of fun. I really would have liked to play the game through all the way, it looked like you had some really fun levels cooked up.