The X-COM series of strategy games has gone through a number of versions, mainly on PC, since its 1994 origins on Amiga, Playstation and PC - but it's now more than 10 years since the last one; X-COM: Alliance.
X-COM: Enemy Unknown began life as a remake of Julian Gollop's classic 1994: UFO: Enemy Unknown, which was released on Sid Meier's now defunct MicroProse label. But the guys at Meier's new company, Firaxis put so much into it that it evolved into a re-imagining.
Enemy Unknown takes place on a modern Earth, under attack from an alien invasion. Facing an unseen enemy of clearly superior technical capabilities, Earth's governments combine to create X-COM. Playing the commander of this global force, your mission is to create an operational base, research alien technologies, organise combat missions, and control your soldiers in battle. You'll dispatch aircraft to intercept and destroy or capture UFOs, and manage ground forces in their battles with alien invaders. All of this is controlled from your XCOM base. Yes, that's base in the singular, unlike the 1994 original, only a single base can be constructed and managed: this adds a strategic element to the game, because your base has to be defended at all costs.
The forces you command are not your own, but like the United Nations, you act a liaison between many disparate governments, and this adds to the tactical aspects of the game.
The Ant Farm view gives you an overview of the XCOM headquarters: you can then zoom in to individual departments to direct specific activities such as research and weapons construction.
Battle strategy takes pace on the Geoscape global view of the world, and you can be directing battle in many theatres of combat simultaneously. Ground combat is turn-based on an isometric-3D playfield. You directly control a squad of four-six soldiers or robots. As you would expect from a modern game, the user interface has been updated considerably from the original game, and gameplay has been tweaked to make it faster and more engaging. Players can make use of suppressive fire and active camouflage during combat.
One-on-one online combat missions enable players to control a squad each, and have a points budget to assemble and equip them before leading them into battle against your human opponent.
The Complete Edition packs in not only the main game, but also all the DLC that's been released to date.