GoldSrc

GoldSrc, or Goldsource, is the retronym used internally by Valve Software to refer to the heavily modified Quake engine that powers their science fiction first-person shooter Half-Life (1998). GoldSrc is a modified version of the QuakeWorld engine codebase, which in turn is a development of the Quake engine codebase. Some minor fixes from the Quake II engine were incorporated as it was developed.GoldSrc is able to render in two API − OpenGL and Direct3D. The successor of the GoldSrc engine is the "Source" engine which powers Half-Life 2. While the engine has no official name, in the months before the release of Half-Life, many computing magazines described the engine as being based upon "Quake Unified Technology". Erik Johnson explains the origin of the GoldSrc name in this quote from the Valve Developer Community: full article at wikipedia