Query: Multiple people were involved in the development of Team Fortress 2.

Relevant passages:
Valve Corporation <=SEP=> Valve Corporation is an American video game developer and digital distribution company headquartered in Bellevue , Washington . The company is known for the Half-Life , Counter-Strike , Portal , Day of Defeat , Team Fortress , Left 4 Dead , and Dota 2 games , and its software distribution platform Steam .   Valve was founded in 1996 as a limited liability company by former Microsoft employees Gabe Newell and Mike Harrington . Their debut product , the PC first-person shooter Half-Life , was released in 1998 to critical acclaim and commercial success , after which Harrington left the company . In 2004 , Valve launched Steam alongside the critically acclaimed Half-Life 2 . By 2011 , over half of digital PC game sales were through Steam , and Valve was the most profitable company per employee in the United States . In 2015 , Valve entered the game hardware market with the Steam Machine , a line of prebuilt gaming computers running SteamOS , a Valve-developed fork of the Debian operating system .

Team Fortress 2 <=SEP=> Team Fortress 2 ( TF2 ) is a team-based multiplayer first-person shooter video game developed and published by Valve Corporation . It is the sequel to Team Fortress , the 1996 mod for Quake and its 1999 remake , Team Fortress Classic . It was released as part of the video game bundle The Orange Box in October 2007 for Microsoft Windows and the Xbox 360 . A PlayStation 3 version followed in December 2007 . The game was released for Windows as a standalone entry in April 2008 , and was updated to support OS X in June 2010 and Linux in February 2013 . It is distributed online through Valve 's digital retailer Steam , with retail distribution being handled by Electronic Arts .   In Team Fortress 2 , players join one of two teams comprising nine character classes , battling in a variety of game modes including capture the flag and king of the hill . The development is led by John Cook and Robin Walker , creators of the original Team Fortress . Announced in 1998 , the game once had more realistic , militaristic visuals and gameplay , but this changed over the protracted nine-year development . After Valve released no information for six years , Team Fortress 2 regularly featured in Wired News annual vaporware list among other ignominies . The finished Team Fortress 2 has cartoon-like visuals influenced by the art of J. C. Leyendecker , Dean Cornwell , and Norman Rockwell , and uses Valve 's Source game engine .   Team Fortress 2 received critical acclaim for its art direction , gameplay , humor , and use of character in a multiplayer-only game . Valve continues to release new content , including maps , items and game modes , as well as community-made updates and contributed content . In June 2011 , it became free-to-play , supported by microtransactions for in-game cosmetics . A ` drop system ' was also added and refined , allowing free-to-play users to periodically receive game equipment and items by use of a random number generator . Though the game had a unofficial competitive scene for many years , support for official competitive play through ranked matchmaking and an overhauled casual experience was added in July 2016 .