絕地要塞
Unofficial, community-made modifications of GoldSrc have also been produced. Notable games include "Natural Selection", "Cry of Fear" and "Sven Co-op", with Valve's "Team Fortress Classic", "Counter-Strike", and "Day of Defeat" all being based on GoldSrc mods of the same names. "Cry of Fear" and "Sven Co-op" have since been released for free as standalone games on Steam.