Team Fortress Classic
Valve developed several games using the GoldSrc engine, many of which were based on original user-made modifications. Valve's "Team Fortress Classic", released in 1999, was developed primarily by two of the developers of the "Quake" mod "Team Fortress". "Counter-Strike" and "Day of Defeat" were also originally "Half-Life" modifications that Valve purchased the rights to and re-released as standalone titles. "Counter-Strike" evolved into its own series with the debut of the Japanese arcade game "Counter-Strike Neo" in 2003 and Valve's own follow-up in 2004, ', both of which run on the GoldSrc engine. Although Valve's further instalments in the series starting with ' use the newer Source engine instead, "Counter-Strike Online" and "", two spinoff titles released by Nexon in 2008 and 2014 respectively, utilize GoldSrc as their basis.