Take on wave after wave off starving zombies. You can use either the WASD or arrow keys to move around, and the mouse to aim and shoot. Press R to reload, Spacebar to access the upgrade menu at the end of a wave, and Q and E to toggle between your weapons. As the waves go on, you will face more and more zombies, who will be faster. Use the map to see where the zombies, marked with red dots, are coming in, and get ready to shoot for your life! There are three difficulties - Easy, Hard, and Nightmare, depending on how adventurous you are.