Counter-Strike is a tactical first-person shooter game developed by Valve. It was initially developed and released as a Half-Life modification by Minh "Gooseman" Le and Jess Cliffe in 1999, before Le and Cliffe were hired and the game's intellectual property acquired. Counter-Strike was released by Valve for Microsoft Windows in November 2000, and is the first installment in the Counter-Strike series. Several remakes and ports were released on Xbox, as well as OS X and Linux.

Half-Life is a 1998 first-person shooter game developed by Valve Corporation and published by Sierra Studios for Windows. It was Valve's debut product and the first game in the Half-Life series. The player assumes the role of Gordon Freeman, a scientist who must escape from the Black Mesa Research Facility after it is invaded by aliens following a disastrous scientific experiment. The gameplay consists of combat, exploration and puzzles.