Valve Corporation (commonly referred to as Valve) is an American video game developer and digital distribution company headquartered in Bellevue, Washington. Founded in 1996 as a limited liability company by former Microsoft employees Gabe Newell and Mike Harrington, the company has developed the critically acclaimed Half-Life, Counter-Strike, Portal, Day of Defeat, Team Fortress, and Left 4 Dead video game series, alongside Dota 2. It also developed and maintains Source on which most of its games run, and the software distribution platform Steam, which has led to the Steam Machine, a line of pre-built gaming computers running SteamOS. A Luxembourg-based office for European regions, Valve S.a.r.l, was opened in 2012.