Half-Life is a science fiction first-person shooter and the prequel to Half-Life 2 developed by Valve Corporation and published by Sierra Studios. It was released on November 18, 1998. Half-Life runs on the GoldSrc engine, a heavily modified version of the Quake engine, licensed from id Software.
The c1, c2, etc. prefixes stand for Chapter 1, Chapter 2, and so on respectively. t0 stands for Training.
There is a total of 103 maps, 7 of which are part of the Hazard Course, and 23 are either skippable or ignored in speedruns.