I played through I like the game and I think the rewind system was very well implemented :). Also completing the levels gives satisfaction. One thing I realised is that I can many cases shoot through at least the corner of the walls which makes it easier to kill the "most dangerous" enemies which would be a supris when I get there. Not sure if that is intended or not. I also liked the arena modes. With some music and a bit better AI this could be a nice stress-realising FPS game :).