Half-Life Level Creation
This page contains articles relating specifically to level design for Half-Life.
Forge Game Data
J.A.C.K. A modified version of the GoldSource Engine created by Russian modders. J.A.C.K. offers many additional features for level editing and modding for Half-Life, as well as Quake 2 and 3.
SLEDGE EDITOR A replacement to Valve's GoldSource Engine, Sledge is still currently in it's Alpha form.