Z-Day, a gamemode for Garry's Mod 10, is an attempt to create a multiplayer zombie-fighting experience that seems believable, yet fun to play. Guns don't appear from thin air; you have to scavenge to find them yourself. Killing zombies isn't the only thing you're worried about; barricading yourself and your friends from the horrors is far more important than going out into a field of zombies, guns blazing. Ammunition is limited, and survival is of chief importance. If you can survive for a map-specified period of time and make it to the map-specified "goal" area before the time is up, you will have successfully survived Z-Day.