Counter-Strike is a popular video game that modifies the multiplayer aspects of Half-Life, making it more team-oriented and providing players with an experience similar to what a real counter-terrorist or terrorist unit would go through. Players join either the Counter Terrorist team or the Terrorist team as they battle against each other in various mission scenarios. The goal of each round is to eliminate all opposing forces or complete objectives while also managing resources such as ammunition, money and health. With its fast pace and intense gameplay, Counter Strike has become one of the most popular online games today.

Counter-Strike: Source is a popular video game from Valve that uses the Source engine. It has recreated maps from Counter-Strike 1.6, such as Office, Havana, Italy, Aztec, Chateau and more with new textures and improved buildings and scenery. Objects in these levels react realistically to the physics engine of the Source engine. The game can be downloaded through Valve's Steam service with Half-Life 2 included in the package.

Counter-Strike: Condition Zero (CS:CZ) is a tactical action video game that requires players to compete with and against AI opponents in mission-based campaigns located around the world. As leader of an elite counter-terrorist unit, players must complete over 20 new missions which include rescuing hostages, escorting VIPs to safety, and locating and defusing bombs. This game uses advanced technologies such as detailed models, atmospheric enhancements like snow or rain, and other dynamic special effects powered by an enriched Half-Life engine. CS:CZ advances the award-winning Counter Strike series by introducing single-player action and online play enhancements for more strategic gameplay.