Zombie Panic! Source is a cooperative survival-horror Half-Life 2 first-person shooter modification. It is the sequel to the Half-Life mod Zombie Panic. Set in the middle of a zombie apocalypse, players start as a small group of survivors attempting to stay alive. Each map will have its own objectives to complete and win the round or survive by a period of time. Initially released on December 28, 2007 via Mod DB page as a public beta (v1.0) and later re-released for Steam via Steamworks in October 8, 2008 as a free-to-play game.