I really liked the art and the rewind gameplay elements are also well done. I wish there was an ending or a score system. Maybe player could get a point every second for each generator standing and the game would get progressively harder? Something to incentivise the player to keep more of them up. Now it is easy to just defend one generator endlessly.
Also, if you're not going for a webGL build, please include Application.Quit(); somewhere :P
PS: I wonder if the Debug.Log("GAME OVER, BITCH"); is still there :P