Source is a 3D game engine developed by Valve. It debuted as the successor to GoldSrc in 2004 with the releases of Half-Life: Source, Counter-Strike: Source, and Half-Life 2. It is most well-known for its usage by Valve, but the engine has been used both by small teams and individuals to create modifications of Valve games, and other studios creating distinct games, notably Troika Games' title Vampire: The Masquerade – Bloodlines. Valve continued to create incremental updates to the Source engine after its 2004 release, most of which coincided with games created by Valve. In the late 2010s, Valve created the Source 2 engine to replace Source, with it publicly debuting alongside Half-Life: Alyx. The Source engine is most well-known for its advancements in physics, AI, and graphics.

Half-Life: Alyx is a 2020 virtual reality (VR) first-person shooter game developed and published by Valve. It was released for Windows and Linux, with support for most PC-compatible VR headsets. Set five years before Half-Life 2 (2004), players control Alyx Vance on a mission to seize a superweapon belonging to the alien Combine. Like previous Half-Life games, Alyx incorporates combat, puzzles and exploration. Players use VR to interact with the environment and fight enemies, using "gravity gloves" to snatch objects from a distance, similarly to the gravity gun from Half-Life 2.