Such a cool game! There seem to be some finnicky bugs about resetting the states of the cubes, but some of that might also be because it's unclear at first that you can only use each action once before they get reset (which isn't always clear). It might be cool if they all had the animation like the gravity cube that dims when they can't be used. Might also make it so having multiple of the same cube allows you to do that action multiple times before being reset (which you may have implemented with double-jumping, but wasn't very clear.
I also had a bug in the boss fight a few times where one of the firing cubes seemed to attach at the same point as another cube and so I just rocketed to the right.
Amazing you were able to accomplish such a polished-looking game in a week!