A re-imagining of the popular and influential 1994 PC title X-COM - UFO Defense, XCOM - Enemy Unknown takes place in the near future when hostile and technologically superior aliens have invaded Earth. To fight back, the world's governments have formed an elite paramilitary organization, and as commander of this "Extraterrestrial Combat Unit," players must coordinate a worldwide effort that includes planning combat missions, controlling the soldiers in battle, researching and reverse-engineering alien technology, and creating and upgrading the XCOM base.
Instead of constructing bases all around the world, gamers conduct business from a massive underground bunker that is sliced in half to offer something of an ant-farm view, and they launch satellites to keep watch over specific countries. When a country is under assault players send in a group of unique soldiers to fend off the invaders in turn-based skirmishes. In battle each character can freely move once per turn, and perform one action per turn as they manoeuvre around highly destructible environments. Gamers can then excavate and install facilities at their base for things like resource collection, alien interrogation, and soldier upgrades, though each successive room costs more to install.
Every decision players make in XCOM - Enemy Unknown has lasting consequences. When soldiers die, they stay dead forever, turning their upgrades and advancements into sunk costs. And with assaults taking place around the globe, gamers must make strategic decisions about where and when they send their limited resources. The only way to truly lose the game is to have eight member countries leave XCOM's council, and abandoning one country in order to save another can result in severe political consequences.
The sole multiplayer option in XCOM - Enemy Unknown resembles a classic "Team Deathmatch" mode, but the action stays varied because gamers are given the option of filling out their roster with units from both sides of the conflict. Ranked matches offer players 10,000 points to spend on six units, their weapons, their gear, and their special powers, while private matches can be customized in any way the participants see fit.