Age of Empires Online was a massively multiplayer, online, real-time strategy game released on August 16, 2011 through digital distribution and optical discs. Based upon the gameplay of the Age of Empires series, it was originally being developed by Robot Entertainment, but on February 24, 2011, it was announced that Gas Powered Games, the creators of Supreme Commander, had taken over production. The game was published by Microsoft.The game was free-to-play—it was free for users to play, with the additional option of earning or purchasing premium content. Premium content included access to many special items and blueprints, and more quests and features. Also, booster packs were available, such as Defense of Crete and Skirmish. The former gave the player the ability to play in a survival type mode game, while the latter allows up to four humans versus up to four CPU opponents in a more traditional skirmish game-mode. The modes could be played in either single-player or co-op. The game also featured several player versus player (PvP) modes for up to four people with the option of a PvP "Champion mode" which fully unlocked the players' tech tree and rendered the gear for aesthetics only.
On March 27, 2012, the game premiered on Steam after a major overhaul patch which addressed complaints of an 'MMO-like grind' and many other features, along with the debut of the Celtic civilization. On June 15, 2012 the premium content system was changed by offering the option to purchase all past and future content through 'Empire points' earned in game, or by purchasing the points directly with real world money. With this change the player now had the option to earn all premium content for free.
As of 3 January 2013, Microsoft ceased further development on the game and no new content was released. However, the existing content and servers continued to function and were supported. A Microsoft representative later announced on the official forums that on August 22, 2013, the Games for Windows – Live Marketplace would be shut down, leaving the game only accessible by current or former players, thus meaning no new players can register and download the game as of that date. Empire Points could still be earned through gameplay, but the ability to purchase them was later removed. In September 2013, it was announced that the game would remain functional until July 1, 2014 when the service would be shut down. The closure was due to the content being too expensive to maintain.