Zombie Panic! Source

Zombie Panic! Source is a zombie apocalypse-based modification of HL2. It is a multiplayer game for the PC where collaboration between survivors is crucial for success. The beginning of any game begins in a room where one can choose to either be a Survivor, a zombie, or a spectator. The majority of players choose Survivor, despite the zombies advantages of respawns, zombie vision, and higher health. After a set amount of time, the game begins. If there aren't enough zombies for the game, a Survivor(s) is randomly chosen to be zombie. Survivors can win by either killing off all zombie lives, or by finishing certain objectives. Zombies win by killing all humans.

Zombie Panic! fetures two types of gameplay: Zombie Panic! Objective, or zpo, and Zombie Panic! Survival, or zps. In zpo, survivors must accomplish certain objectives, such as finding keys, turning on a generator, or removing a blockade, while surviving attacks by zombies. In zps, zombies start off with a number of lives appropriate for the number of players in the game. Humans must kill all the zombies as well as remove all zombie lives. Zombies gain a life when a survior is killed, while zombies lose a life when a zombie is killed.