Half-Life 2 is a 2004 first-person shooter (FPS) game developed and published by Valve Corporation. It was published for Windows on Valve’s digital distribution service, Steam. Like the original Half-Life (1998), Half-Life 2 is played entirely from a first-person perspective, combining combat, puzzles, and storytelling. It adds features such as vehicles and physics-based gameplay. The player controls Gordon Freeman, who joins a resistance to liberate Earth from the Combine, a multidimensional alien empire.

Half-Life 2 was created using Valve’s Source game engine, which was developed simultaneously. Development lasted five years and cost US$40 million. Valve’s president, Gabe Newell, set his team the goal of redefining the FPS genre. They integrated the Havok physics engine, which simulates real-world physics, to reinforce the sense of presence and create new gameplay. They also developed the characterisation, with more detailed character models and animations.