Deus Ex: Invisible War is an action role-playing video game developed by Ion Storm and published by Eidos Interactive. Released simultaneously for Microsoft Windows and the Xbox video game console on December 2, 2003, the game is a sequel to the critically acclaimed Deus Ex. The game takes place twenty years after Deus Ex, in a world being rebuilt after a catastrophic event called "The Collapse." Following a terrorist attack that destroys the city of Chicago, the player assumes the role of Alex D, a trainee at the Tarsus Academy, whose support is sought by several organizations. As the game progresses, the player learns of conspiratorial factions which seek to drastically change the world. Invisible War was designed to allow player choice in both plot and gameplay, with branching plot lines and emergent gameplay elements. Upon its release, the game received high critical acclaim for its graphics, gameplay and freedom of choice, but criticism was directed towards below-par enemy AI and design choices that made the game seem over simplified. As of April 2011, the game has sold over 1.2 million copies. The game was eventually followed by a 2011 prequel to both it and the original game called Deus Ex: Human Revolution.