i finally got around to playing it and it's great! The concept is fantastic and the rewind animation is super clean!
I could imagine an iteration of this with a heavier focus on boss battles with barely telegraphed attacks (not randomized), that way each time the player rewinds they learn what to expect, and after a bit of practice the player can get through incredibly complex and choreographed battles that seemed impossible at first. i think that would be insanely rewarding.
Like Minit, but bullet-hell. That sounds like an amazing elevator pitch for a game :)
Great idea, great execution. nice job!!