Counter-Strikeis afirst-person shootervideo gamedeveloped byValve Corporation. It was initially developed and released as aHalf-Life modificationbyMinh "Gooseman" LeandJess "Cliffe" Cliffein 1999, before Le and Cliffe were hired and the game's intellectual property acquired. Counter-Strikewas first released by Valve on theMicrosoft Windowsplatform in 2000. The game later spawned a franchise, and is the first installment in theCounter-Strikeseries. SeveralremakesandPortsofCounter-Strikehave been released on theXboxconsole, as well asOS X andLinux. Set in various locations around the globe, players assume the roles of members of combating teams that includecounter-terroristsandterrorists. During each independent match, the two teams of five players are tasked with defeating the other by the means of either achieving the map's objectives, or else killing the enemy combatants. Each player may customize their arsenal of weapons and accessories at the beginning of every match, with the currency earned through each map reset, killing other players and achieving objectives.The game was the most playedHalf-Lifemodification in terms of players, according toGameSpyin 2008.As of December 2013, theCounter-Strikefranchise has sold over 35 million units.