Enjoyed this very much! Felt like a better version of Superhot. I hope you flesh this out more -- really love this concept and style! Very fun! Would like to see more levels, enemy types, and weapons (melee maybe?).
Only (minor) issues are that the grenade enemies are a bit cheap sometimes -- maybe could use temporary immunity after rewinding. I also thought the guns felt wimpy. Something about how the bullets move didn't jive with me, particularly in the pistol.I think that if weapons had slightly higher damage output,then it could lead to faster paced gameplay and they would feel more rewarding to use. I also haven't the first clue about how to design a game so I could be completely wrong. Not trying to be an armchair developer.
Either way, keep up the good work! Really great stuff here.