It took me a couple of deaths to realise that the controls are static UP, DOWN, LEFT, RIGHT and not based on the ships forward direction, that was a bit jarring. I have a feeling you're moving the enemy space ships using the Update() function and not offsetting by Time.Deltatime? I can't actually play the game and this shows you why:
I got bumrushed by 3 enemies while testing the rewind and I'm fairly certain they shouldn't be coming towards me while I'm in that state.
Your projectiles are also not shooting from the correct point, I am facing forward but its shooting backwards:
I love the visuals but I can't submit a rating for that alone so I haven't left one.