Call of Duty 2 is a 2005 first-person shooter video game developed by Infinity Ward and published by Activision in most regions of the world. It is the second installment of the Call of Duty series. Announced by Activision on April 7, 2005, the game was released for Microsoft Windows on October 25, 2005, and as a launch title for the Xbox 360 on November 22, 2005. Other versions were eventually released for OS X, mobile phones, and Pocket PCs. The game is set during World War II and the campaign mode is experienced through the perspectives of four soldiers: one in the Red Army, one in the United States Army, and two in the British Army. It contains four individual campaigns, split into three stories, with a total of 27 missions. Many features were added and changed from the original Call of Duty, notably regenerating health and an icon that indicates a nearby grenade about to explode. The game drew critical praise, particularly for the graphics, sound, and the regenerating health system. The Xbox 360 version sold more than 250,000 copies in its first week, more than two million copies by January 2008, and nearly six million copies by November 2013. Retrospective reviews have been positive, with critics praising the game's improvements over its predecessor and innovations that become the series' mainstays, although some have found it dated. It is considered to be one of the Xbox 360's best games and one of the best video games of all time.