Valve Corporation

Valve Corporation is an American video game developer and digital distribution company founded in 1996 by Gabe Newell and Mike Harrington. It created the Steam platform and games including Half-Life, Portal, and Counter-Strike.

Steam: Steam is Valve’s digital storefront and software platform for distributing games, updates, and community features. Valve built Steam into its central distribution platform and a major part of its business.
Gabe Newell: Gabe Newell is an American game developer and co-founder of Valve Corporation. He left Microsoft with Mike Harrington to establish Valve in 1996.
Digital distribution: Digital distribution delivers software and media over networks instead of through physical retail copies. Steam made this distribution model central to Valve’s business.
Electronic Arts: Electronic Arts is an American video game publisher and developer founded in 1982. Its publicly traded, large-scale publishing model contrasts with Valve’s privately held structure.
PC game modding: PC game modding is the practice of modifying or extending video games, often with player-created tools and content. Mods for Valve games helped produce new games and communities.
Source engine: Source is a family of game engines developed by Valve for creating and running video games. Valve developed this engine to power several of its games and support community-made content.
Mike Harrington: Mike Harrington is an American software developer and co-founder of Valve Corporation. His partnership with Gabe Newell launched the company and its first game.
Steam Workshop: Steam Workshop is a Steam service for sharing and distributing user-created game content. It lets communities create and circulate content for supported Valve games.
Epic Games: Epic Games is an American video game and software company known for Fortnite and Unreal Engine. Epic competes with Valve through its own PC game store and developer ecosystem.
Team Fortress: Team Fortress is a multiplayer shooter series that began as a modification of Quake. Valve acquired its creators and developed Team Fortress 2 as a lasting service game.

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Half-Life 2Related: Valve developed and published the game.