Wolfenstein is a first-person shooter video game developed by Raven Software and published by Activision, part of the Wolfenstein video game series. It serves as a loose sequel to the 2001 entry Return to Castle Wolfenstein, and uses an enhanced version of id Software's id Tech 4. The game was released in August 2009 for Microsoft Windows, PlayStation 3 and Xbox 360. Wolfenstein received lukewarm to positive reception by critics and suffered from poor commercial sales; selling a combined 100,000 copies within its first month. It would be the final game id Software oversaw as an independent developer, released two months after their acquisition by ZeniMax Media in June 2009. The game would be loosely succeeded by Wolfenstein: The New Order, released on May 20, 2014. The story is set in the fictional town of Isenstadt during World War II, which the Nazis have enforced martial law in order to excavate rare Nachtsonne crystals necessary to access the "Black Sun" dimension. As the game progresses, happenings in Isenstadt become stranger (military patrols are replaced by supernatural creatures, etc.). Locations include the town's sewers, a tavern, a hospital, a farm, an underground mining facility, a church, the SS headquarters, a dig site and caverns, a cannery, a radio station, a paranormal base, a general's home, a castle, an airfield and a large zeppelin. In an introduction sequence, special agent William "B.J." Blazkowicz steals a medallion from a general on the German battleship Tirpitz. Discovered and captured, he unwittingly unleashes the power of the medallion, which kills all his foes for him. Hijacking a plane from the Tirpitz, he escapes and returns to the OSA headquarters. During a meeting there, he learns that the medallion needs crystals called Nachtsonne, mined only in a city in Germany called Isenstadt, to make use of its full power. The Nazis have begun digging for crystals, led by a general named Viktor Zetta. He also hands over the medallion to the OSA for further research.