Publisher Microsoft Studios released the first title of the Age of Empires franchise in 1997. Age of Empires was one of the first historically-based real-time strategy games (RTS) and is considered the creator of the historical sub-genre. In Age of Empires players assume command of a small Stone Age tribe and guide them through centuries of development. The ultimate goal is to build an Iron Age empire capable of world dominance. Age of Empires was one of the first RTS titles to adopt the 4X style of gameplay in which players assume control of an empire and "expand, explore, exploit and exterminate." This style became a trend in the RTS genre. Age of Empires offers a gameworld with tremendous depth. Players choose from a selection of twelve civilizations each with unique strengths and attributes. Gameplay is based on micromanagement and strategy. Players build and expand their city, manage resources, establish trade relations, build and command an army, and master new technology. Players may engage in historical missions or use a randomly generated map to create their own unique scenario. Multiplayer mode allows eight players to play at once, either as teammates or competitors. Age of Empires was an immediate commercial success at the time of release and inspired a legendary franchise. The series culminated in three installments and four expansion packs. It inspired a spin-off series, Age of Mythology, and an online game entitled Age of Empires Online which launched in 2011.