Quite creative idea, and the assets are really well made. Though i feel as if this needs some more polish, the game feels a little bit unresponsive and after a while i'm just unloading damage into an army of bullet spunges that just won't die. And the hight ammount of hp makes it feel quite low risk, i'd say reduce the ammount of hp to emphasise the fact you are the last tower.
Still great team effort, keep it up