Counter-Strike originated as a Half-Life modification and has since expanded into a series of games. It pits counter-terrorists against terrorists across rounds, with each team trying to complete a mission objective or eliminate the opposing force. The game is based on two teams - terrorists must plant a bomb while counter-terrorists try to defuse it. Players can choose from different guns like pistols, machine guns, and rifles. Modifications have also been created to change gameplay modes and add new scripts.