XCOM: Enemy Within is an expansion pack for the turn-based tactical video game XCOM: Enemy Unknown. The expansion pack primarily adds new gameplay elements to the base game, as well as introducing new themes of transhumanism via aggressive gene therapy.
XCOM: Enemy Within was released for Microsoft Windows, PlayStation 3, and Xbox 360 in November 2013. In June 2014, Feral released both XCOM: Enemy Within and its base game XCOM: Enemy Unknown for Linux. The game also came to the iOS App Store and Google Play Store a year after the initial release, on November 12, 2014. On March 22, 2016, the game was released on the PlayStation Store for PlayStation Vita.
The Windows, OS X and Linux editions require XCOM: Enemy Unknown to play; Enemy Within was released for Xbox 360 and PlayStation 3 as part of the Commander Edition bundle with Enemy Unknown. The iOS and Android versions were released as stand-alone apps not requiring the original mobile port of Enemy Unknown to play. The PlayStation Vita version is only available bundled with Enemy Unknown under the title, XCOM: Enemy Unknown Plus.