Half-Life Episode 4

Half-Life is a 1998 first-person shooter (FPS) game developed by Valve Corporation and published by Sierra Studios for Windows. It was Valve's debut product and the first game in the Half-Life series. The player assumes the role of Gordon Freeman, a scientist who must escape from the Black Mesa Research Facility after it is invaded by aliens following a disastrous scientific experiment. The gameplay consists of combat, exploration and puzzles.

Valve was disappointed with the lack of innovation in the FPS genre, and aimed to create an immersive world rather than a "shooting gallery". Unlike other games at the time, the player has almost uninterrupted control of the player character; the story is mostly experienced through scripted sequences rather than cutscenes. Valve developed the game using GoldSrc, a heavily-modified version of the Quake engine, licensed from id Software. The science fiction novelist Marc Laidlaw was hired to craft the plot and assist with design.

Half-Life received acclaim for its graphics, gameplay and narrative and won more than 50 PC "Game of the Year" awards. It is considered one of the most influential FPS games and one of the greatest video games ever made. By 2008, it had sold more than nine million copies. It was ported to the PlayStation 2 in 2001, along with the multiplayer expansion Decay, and to OS X and Linux in 2013.