The game is about being trapped in a bunker with a zombie virus and trying to find a way out. You must find a generator to open the door, a flashlight to illuminate the dark bunker, and weapons to kill the zombies in order to make it to the exit.
The generators must be put in order and often require a password to be entered as well. The clues to this are left to the player to find on their own.
Guns and bullets are very important, so you'll also need to find items to kill the zombies along the way.