Dungeons & Dragons Online (DDO) is a massively multiplayer online role-playing game (MMORPG) developed by Turbine for Microsoft Windows and OS X. The game was originally marketed as Dungeons & Dragons Online: Stormreach, then renamed Dungeons & Dragons Online: Eberron Unlimited upon switching to a hybrid free to play model, and was finally rebranded Dungeons & Dragons Online, with the introduction of Forgotten Realms-related content. Turbine developed DDO as an online adaptation of Dungeons & Dragons (D&D), based loosely on the D&D 3.5 rule set. The game is set on the unexplored continent of Xen'drik within the Eberron campaign setting, and in the Kingdom of Cormyr within the Forgotten Realms campaign setting.