I really wanna play this, it would make a neat RP (As long as you don't let any of those "i'm gonna be your son who didn't take no for an answer when he joined marines" in it
Also you should put quiet, distant sounds of people screaming or crying as if there were civilians running away or getting killed.
Or it could be nothing at all but a simple, sad survival.
I'm going for a straight down survival, with a theme of being the last survivors on earth.
I might add a mechanic where, when theres only 1 person left, everything goes in real slowmotion, and the second a zombie simply touches that player, the player loses all their weapons and is knocked down with dramatic music, AKA the piano music in the background becomes 20% more saddening.