What engine did the original "Half-Life" run on?

The original Half-Life game ran on the GoldSrc engine. Developed by Valve, GoldSrc was a heavily modified version of the Quake engine, featuring enhanced graphics, improved AI, and robust physics capabilities. It revolutionized first-person shooter games with its immersive narrative, realistic mechanics, and interactive environments. Its success paved the way for future Valve games and the subsequent development of the Source engine.