The origins of the X-COM game series lie with the 1994 game titled UFO: Enemy Unknown, whose success spawned a rebranding into X-COM: UFO Defense and the launch of five further game titles under the same brand until changes in the ownership of the franchise stopped its development in 2001. After a hiatus, the franchise was bought by 2K Games to be rebooted and reimagined in 2012 as XCOM: Enemy Unknown, so far spawning two more games and additional download contents. The main entries in the series are round-based strategy games, in which players move tactical units over conflict maps in order to fulfill strategic objectives.