résumé
XCOM: Enemy Unknown will place you in control of a secret paramilitary organization called XCOM. As the XCOM commander, you will defend against a terrifying global alien invasion by managing resources, advancing technologies, and overseeing combat strategies and individual unit tactics.
The original XCOM is widely regarded as one of the best games ever made and has now been re-imagined by the strategy experts at Firaxis Games. XCOM: Enemy Unknown will expand on that legacy with an entirely new invasion story, enemies and technologies to fight aliens and defend Earth.
You will control the fate of the human race through researching alien technologies, creating and managing a fully operational base, planning combat missions and controlling soldier movement in battle.