Really cool idea, and the past player looping is pretty cool, I just feel like he comes in a bit late, giving little time to experience that mechanic. Also the camera is a bit jumpy, giving a bit of vertigo, maybe its my mouse sensitivity, but it might be a good idea to limit how far you zoom towards your aim.
All in all I did like it (the enemies seemed interesting too) but the camera made it hard for me to play longer unfortunatly.