An alternative engine for Half-Life based games (source files)
xash3d_source-0.20~git-1-source
Xash3D Engine is a custom Gold Source engine rewritten from scratch. Xash3D is compatible with many of the Gold Source games and mods and should be able to run almost any existing singleplayer Half-Life mod without a hitch. Xash3D FWGS is a fork of Xash3D Engine, which aims on crossplatform and compatibility with original Xash3D and Gold Source.