The aesthetics of the games, enemies and feel is perfect and loved the music. The game is really fun. I havent found too much use to the rewind ability, but the rewind shield is pretty useful (especially against the boss)
But the one thing that the game lacks (and its really noticeable) is sound effects. something simple, even made with BFXR (it's free, check it out) would add A LOT to the game, (Shoot sounds, hit sounds, Spawn Sounds, Pick Up Sounds)
another bug, if you press enter multiple times, the text appears multiple times and ruins the loading intro
But Overall, the game is incredible and really fun, excellent job :D