You are trapped in a graveyard.
Unlike the zombies that are out to eat your brains. You can't stay awake forever. Your gonna need to kill zombies for adrenaline. But zombies can't die. So your gonna need as much ammo and guns as you can find. Lucky for you the graveyard can supply you. You also have a counter to keep track of all the zombies you put down, if only temporarily. A "playtime" counter is also displayed so you don't miss any important meetings.