The Orange Box is a compilation that contains five games, all powered by Valve's Source engine. The games included are: Half-Life 2, Half-Life 2: Episode One, Half-Life 2: Episode Two, Portal and Team Fortress 2. Two of the games included, Half-Life 2 and its first stand-alone expansion, Episode One, had previously been released as separate products. Three new games were also included in the compilation: the second stand-alone expansion, Half-Life 2: Episode Two, the puzzle game Portal, and Team Fortress 2, the multiplayer game sequel to the original mod based on the Quake engine, Team Fortress.