Codex Gamicus
GoldSrc Engine
Basic Information
Valve Corporation

The GoldSrc Engine (also known as the Goldsource Engine) is a heavily modified version of the Quake Engine. It was developed by Valve Corporation and it was used to develop Half-Life, Half-Life: Opposing Force, Half-Life: Blue Shift, Counter-Strike, Counter-Strike: Condition Zero, Day of Defeat, Ricochet and Deathmatch Classic.