Call of Duty: World at War, developed by Treyarch, is the fifth installment of the main series. Released after Modern Warfare, it returns to the World War II setting of earlier titles, featuring the Pacific theater and Eastern front. The game uses the same proprietary game engine as Call of Duty 4 and was released for the PC, PlayStation 3, Wii, Xbox 360 consoles and the Nintendo DS handheld in North America on November 11, 2008, and November 14, 2008 in Europe. As of June 2009, Call of Duty: World at War has sold over 11 million copies. It acts as a prologue for Treyarch's next game, Black Ops, which is in the same universe, sharing characters and story references.