Garry's Mod is a sandbox physics game using a modified Source engine. Garry's Mod has been available on Valve's content delivery service, Steam. Garry's Mod used to require the user to own at least one game on Steam based on the Source engine. It is also commonly used for the creation and publishing of videos on YouTube. Garry's Mod was originally a modification for Valve's Half-Life 2, but was later made into a standalone Steam game. A...

Team Fortress 2 is a team-based first-person shooter (FPS) multiplayer video game developed by Valve Corporation. It is a sequel to the original mod Team Fortress based on the Source engine. Team Fortress 2 is distributed online through the Steam system, while retail distribution was handled by Electronic Arts. Team Fortress 2 is the first of Valve's multiplayer games to provide detailed statistics for individual players.