What is the Gold source engine?
The gold-source engine is a physics engine developed by Valve software back in 1998
It was the primary focus for valves Breakthrough title Half-Life, and was even used by Gearbox Software when developing James Bond 007: Nightfire.
It is based from ID software's Quake engine but with enough modifications to make it unique and revolutionary for its time.
While Its sequal (Half-Life 2) Might have blown this games engine out of the water its still important to remember what came before.