The 2004 Valve game that returned Gordon Freeman and showcased the Source engine was Half-Life 2. Valve released it for Windows on November 16, 2004, after a lengthy and highly publicized development period.
The first-person shooter continues the story of physicist Gordon Freeman, who awakens years after the events of Half-Life and joins a resistance against the Combine. Its setting includes the dystopian City 17 and introduces major characters such as Alyx Vance.
Half-Life 2 was noted for environmental storytelling, facial animation, detailed physics, and the Gravity Gun. The Source engine powered these systems and later supported many other Valve games, including Counter-Strike: Source and Portal.
The game was distributed through Steam, which Valve used to manage activation and updates. Its episodes expanded the story, but Half-Life 2 itself remains distinct from Half-Life 2: Episode One and Episode Two.