The concept is really cool and i like how i need to switch between attacking and collecting.
i couldn't get passed level since it got too hard. first of all some enemies spawn too close to the wall and so the rewind won't help you.. and boom -40 hp :) throw a boss on top of it and you got an impossible level to beat
i would considering adding a ranged attack to help you attack the boss and get to far away enemies as an alternative to the rewind ability because of its programmed limitations.
artwork is great and gamplay is fund but needs balancing :)
cheers friend!