Valve ported Half-Life to its Source engine in 2004, while a third-party remake, Black Mesa, was released in 2020. It was ported to the PlayStation 2 in 2001, along with another expansion Half-Life: Decay, and to macOS and Linux in 2013. It was followed by the expansion packs Opposing Force (1999) and Blue Shift (2001), developed by Gearbox Software. By 2008, it had sold over 9 million copies. It won over 50 PC ' Game of the Year' awards and is considered one of the most influential FPS games and one of the best video games ever made. Half-Life received acclaim for its graphics, realistic gameplay and seamless narrative. Science fiction novelist Marc Laidlaw was hired to shape the story and assist design.

They developed using GoldSrc, a heavily modified version of the Quake engine, licensed from id Software.

Valve co-founder Gabe Newell said the team were disappointed with the lack of innovation in the FPS genre, and aimed to create an immersive world rather than a 'shooting gallery'. Unlike many other games at the time, the player has almost uninterrupted control of the player character, and the story is told mostly through scripted sequences seen through his eyes. The core gameplay consists of fighting alien and human enemies with a variety of weapons and solving puzzles. Players assume the role of Gordon Freeman, a scientist who must escape the Black Mesa Research Facility after it is invaded by aliens. It was Valve's debut product and the first game in the Half-Life series. Half-Life is a first-person shooter (FPS) game developed by Valve and published by Sierra Studios for Windows in 1998.

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