Counter-Strike (CS) is a series of multiplayer tactical first-person shooter video games, in which opposing teams attempt to complete various objectives. The series began on Windows in 1999 with the release of the first game, Counter-Strike. It was initially released as a 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.