A genuinely really creative idea!
My only gripe is how the movement can feel a little delayed and therefore unresponsive. It seems like you're using the delta of the mouse position, meaning if the invisible mouse gets stuck on the bottom of your screen you can no longer move your character downward. Perhaps if you decide to continue working on this game afterward you could play around with just using mouse position or something like that?
Either way, still a really fun game, haven't seen one like this in the jam yet! Great job!