Zombie Panic! Source is a co-op oriented Survivor Vs Zombie multi-player survival horror modification for HL2. While our main priority is to make the mod as fun to play as possible, ZP:S plans to greatly expand on the core features of "Zombie panic" For HL1, with the obvious new features, impressive visuals, and of course atmospheric maps. More importantly ZP:S will not force players to fend against dumb and predictable AI, but instead keep the same intense thrill of surviving against intelligent and persistent player controlled zombies as the original.
A new map titled ZPO_Corpsington for Zombie Panic: Source