In XCOM: Enemy Unknown an aggressive alien race has decided to colonize Earth. To defend our world, a special organization, the Extraterrestrial Combat Unit, has been formed. Its main objective is not only to drive the aliens back, but also to learn from their technologies. You are appointed the leader of this organization.
The gameplay is organized into two levels: strategic, where you research new technologies and examine the aliens' biology among other things, and turn-based, where you fight aliens in face-to-face confrontation.
As every XCOM action has a cost, you need to raise funds. The only way to do this is to satisfy those countries which sponsor your organization with your work.
Establish your base - choose a continent (each of which gives you a different bonus), hire employees and expand rooms and laboratories.
When alien activity is detected, send your unit to eliminate the threat. This is where the gameplay changes into a turn-based strategy game. Lead a small group of highly trained soldiers and kill every alien you find on the map. Remember that each soldier has their own line of sight, and that some enemies will hide in the fog of war. Your soldiers will gain experience with success, but if they fail, you cannot resurrect them.