Half-Life is a game developed in the late 1990s by
Valve Software, a development team whose members include ex-
Microsoft employees as well as
Doom level-scene veterans. The game uses the original
Quake engine, with the addition of coloured lighting, some simple reflection and translucency effects, and a heavily rewritten software renderer (which allows the game to be run at a playable framerate on pretty much any modern PC).
The sound engine is also greatly enhanced, and includes excellent and convincing positional audio and doppler effects. They most immediately apparent enhancements however are the convincing enemy AI and the liberal sprinkling of in-engine scripted sequences which are triggered as you enter new areas. The Doom mindset is apparent as well, with the first few areas of the game having a resolutely single-storey layout. There are a wide range of realistic weapons, and the by now de rigeur rock-solid networking code.
All these great features brought together in one place led to Half-Life having possibly the most active and ambitious mod community of any FPS. Mods such as Team Fortress and Counter-Strike totally reinvent the game for net play, and more recently the mod Gunman Chronicles has been expanded into a fully-fledged commercial game.
In the single player game, you play Gordon Freeman, a research scientist working in a secret government lab with strange alien materials. Very early on, disaster strikes and you have to fend off alien attackers and the US military. The plot, as it is, was raved about at the games release, but is in fact fairly humdrum, rigidly linear and doesn't make a huge amount of sense. No matter though, as it serves its purpose admirably.
HL is one of the best games of the 1990s, and reinvented the stagnating FPS genre. By combining great technology with professionalism and the good points of console and PC action games, Valve created a benchmark title.
As I'm tired of answering this, here is the answer as listed on the unofficial Half-Life
FAQ (http://www.netdoor.com/half-life/downloads/HLFAQ.html#2.1.10)
Valve originally licensed the source for Quake from id Software and they began working on that code around October of 1996. Between that time and the time they finished Half-Life in October of 1998, they modified/removed/created something like 70% of the code.
Note: That's the Quake
1 source/engine. Nearly all the new
modelling,
animation,
lighting and
sound (and what-have-you) subsystems, in software and hardware rendering modes, were done by Valve. Purists would take this to mean that you can license an engine to get a good game, but you must build upon it to make a great one.