Cool game
I was waiting for a pause to buy upgrades and it didn't come (maybe I just didn't play long enough though). Would be cool if it was separated into "levels" and you could buy upgrades in between or at least if the game paused when you went to buy upgrades. If you're not sure how to do that, you can probably just set Time.deltaTime to 0 and the game will pause itself (and then set it back to 1 to unpause).