IMPORTANT: To skip the instructions at the beginning, hold S while you click the green flag. Click to shoot the revolver. Press M to open or close the map to check where the zombies are. If you get a grenade, press space when a zombie is approaching to use it. You can only hold one at once. The zombies will move faster and get more powerful as the game progresses.
Credits: Me (Colin) Bugs: Sometimes if you defeat a zombie with a grenade and get a grenade as an item immediately after, the second grenade will be wasted. (May be fixed, but uncertain) Sometimes the game will soft lock and the zombie will be frozen in the middle of the screen. It can't deal damage, but it can't die. To fix this, press 3 to reset the zombie's health to 1000. Keep in mind that this will not grant you any advantage. It is strictly for fixing the soft lock. (May be fixed, but uncertain)