Team Fortress originally began life as a free mod for Quake. Development on Team Fortress 2 switched to the GoldSrc engine in 1998 after the development team Team Fortress Software—consisting of Robin Walker and John Cook—were first contracted and finally outright employed by Valve Corporation. At the point of Team Fortress Software's acquisition production moved up a notch and the game was promoted to a standalone, retail product; to tide fans over, work began on a simple port of the game which was released in 1999 as the free Team Fortress Classic. Notably, Team Fortress Classic was built entirely within the publicly available Half-Life Software Development Kit as an example to the community and industry of its flexibility.
Walker and Cook had been heavily influenced by their three month contractual stint at Valve, and now they were working full-time on their design, which was undergoing rapid metamorphosis. Team Fortress 2 was to be a modern war game, with a command hierarchy including a commander with a bird's-eye view of the battlefield, parachute drops over enemy territory, networked voice communication and numerous other innovations.
Original Style of TF2