I thought that was really good!
Things I liked:
>Cool concept! I really liked the use of the rewind mechanic to attack (maybe I'm biased cause it reminds me of my game :P )
>Was fun and challenging in the later levels
>The quick level restarts :) Kept me engaged after I'd died :)
>The graphical effects :) Sure the character and enemies were a bit simple, but the use of post processing, particles and screen shake elevated the visual feel of the game substantially :)
Things to improve:
>Maybe add more enemy types? (like ones that aren't required to unlock the level end but keep moving while you're rewinding for example?)
>Maybe increase the movement speed of the enemies? (or make a faster enemy type) It felt like after I'd gotten rid of a couple of enemies that I could just outrun the remaining ones)
I really like the idea! I had fun playing it! Well done!