Team Fortress (TF) is a team- and class-based multiplayer online first-person shooter video game mod based on id Software's Quake Engine, and later QuakeWorld Engine. Team Fortress, also known as Quake Team Fortress (QTF), and later QuakeWorld Team Fortress (QWTF), was designed and written by Robin "Bro" Walker, John "Jojie" Cook, and Ian "Scuba" Caughley in 1996. Because of its popularity, it has spawned an endless amount of mods for not only Team Fortress, but other games as well. Valve took an interest in the Team Fortress Software organization and hired the three creators to work on a Team Fortress Half-Life mod, and later a standalone version called Team Fortress Classic (TFC), released in 1999. A standalone sequel to Team Fortress Classic, Team Fortress 2 (TF2), was developed by Valve and released in 2007.
To this day, some people still participate in Team Fortress servers. The most active communities run server-side mods such as Custom TF and MegaTF. Team Fortress has also spawned many mods replicating its formula for other games, such as Quake III Fortress, Enemy Territory Fortress, etc.
Team Fortress has a high emphasis on teamwork and cooperation involving two teams (red and blue), with nine classes on each team. Some maps have an extra two teams (yellow and green); later games in the series, such as Team Fortress Classic, only include a red team and a blue team. The players battle each other to complete objectives in game modes like Attack/Defend and Capture the Flag. Team Fortress has these ten classes available to each team: Scout, Sniper, Soldier, Demolitions Man, Combat Medic, Heavy Weapons Guy, Pyromaniac, Civilian (Escort only) Spy and Engineer.