Thanks for the detailed review. The rewinding is based on your score so 10 points per second. If you have 100 score or more you can rewind the full 10 seconds if not it will be less depending on your score. We didn't have much time to do the enemy spawn so it was a bit of a rush job but will fix it on the later updates. Also the enemies move with a simple script so I had to make it so they float so well incase they got stuck in walls. So to counter that the player can shoot up.
Anywho, thanks alot for trying my game out. I will try to get all the ending for your game when I have some free time :D