Call of Duty (release October 29, 2003) is a first-person shooter video game based on the Quake III: Team Arena engine. This war game simulates the infantry and combined arms warfare of World War II. The game was published by Activision and developed by Infinity Ward. It was accompanied in September 2004 by an expansion pack, Call of Duty: United Offensive, which was produced by Activision, and developed by Gray Matter Interactive, with contributions from Pi Studios. The Mac OS X version of Call of Duty was ported by Aspyr Media. In late 2004, the N-Gage version was developed by Nokia and published by Activision. Other versions were released for PC, including Collector's Edition (with soundtrack and strategy guide), Game of the Year Edition (includes game updates), and the Deluxe Edition (which contains United Offensive expansion and soundtrack in the USA. In Europe the soundtrack is not included).