Call of Duty 4: Modern Warfare is a first-person shootervideo game, developed by Infinity Ward and published by Activision for Mac OS X, PlayStation 3, Windows, and the Xbox 360. It is the fourth installment of the Call of Duty video game series, excluding expansion packs. The game breaks away from the World War II setting of previous games in the series and is instead set in modern times. The game is the first in the series to be rated Mature in North America. The title and game details were announced on April 25, 2007,[10] and the game was released worldwide between November 6, 2007 and November 9, 2007. It became available on Steam on November 6, 2007 for pre-purchase, and was available to play on November 12, 2007.[11] It was released on September 26, 2008 for Mac OS X.[1] The game was in development for two years. It uses a proprietary game engine that includes features such as true world-dynamic lightning, HDR lighting effects, dynamic shadows, and depth of field.[12]