Half-Life is a first-person shooter computer game developed by Valve Software and published by Sierra On-Line in 1998, based on a heavily-modified core Quake I game engine. It was first published for PCss running Microsoft Windows, and was later ported to Sony's Playstation 2 video game console (a version for Sega's Dreamcast was completed, but never released commercially). Half-Life was heralded by computer game critics for its gripping storyline, which would influence the development of other first-person shooters in the years to come.
In the game, you play a scientist named Gordon Freeman who is a survivor of an experiment gone horribly wrong, allowing aliens from another planet to invade Earth. As you try to escape the destroyed facility you soon discover that you are caught between two sides: the aliens, and the forces of the United States military which has been dispatched to cover up the experiment - including you.
Two expansion packs have been been released: Opposing Force and Blue Shift. In 1999's Opposing Force, you play through the world of the original storyline once again, but this time as one of the military officers sent to cover up the experiment. Blue Shift (2001) returns the player to the original storyworld yet again, this time as one of the facility's guards. (This expansion was originally developed as a bonus mission for the canceled Dreamcast version.)
Half-Life has also been used as a base for many modss (add-ons) such as the immensely popular and free multiplayer mod, Counter-Strike. Other popular mods include Team Fortress Classic, Day of Defeat, Action Half-Life and Natural Selection.
Half-Life 2 was merely a rumor until a strong impression at E3 in May 2003 launched it into levels of hype only equalled by DOOM³. The story takes place after the Black Mesa incident in a futuristic Eastern European 'City 17'. It again pits Gordon Freeman against an alien invasion. It was due to come out in September 2003, but has been delayed; Valve Software have suggested that a release date of March 2004 is more likely. This pushing back of Half-Life 2's release date came in the wake of the cracking of Valve's internal network, through bugs in Microsoft Outlook, resulting in the theft of the game's source code. While of great interest to the abjectly curious for simple learning purposes, this has likely hurt Valve's abilities to license their game engine to other companies for their own products. It uses a new engine entitled 'Source', featuring some of the most advanced graphics to date.