Half-Life 2: Episoe One is the first of a trilogy of episodes for the 2004 first-person shooter game, Half-Life 2. It was developed by Valve Corporation and was released on June 1, 2006. The episode is a standalone game; while a continuation of Half-Life 2, it does not require the original game to be installed or registered to a user's online Steam account to play. It takes advantage of several major upgrades to the Source game engine since the release of Half-Life 2.