A previous version of Condition Zero that was developed by Ritual Entertainment was released alongside it as Condition Zero: Deleted Scenes. The original Counter-Strike was followed by Counter-Strike: Condition Zero, developed by Turtle Rock Studios and released in March 2004. It was initially released as a modification ('mod') for Half-Life that was designed by Minh 'Gooseman' Le and Jess 'Cliffe' Cliffe before the rights to the mod's intellectual property were acquired by Valve, the developers of Half-Life, who then turned Counter-Strike into a retail product released in 2000.
The series began on Windows in 1999 with the release of the first game, Counter-Strike. Counter-Strike ( CS) is a series of multiplayer tactical first-person shooter video games in which teams of terrorists battle to perpetrate an act of terror (bombing, hostage-taking, assassination) while counter-terrorists try to prevent it (bomb defusal, hostage rescue, escort mission).