Final Fantasy XIII is a role-playing game for high-def consoles, set in an original universe that blends futuristic technology and ancient mysticism. Created ages earlier by godlike mechanical titans called the fal'Cie, the mystical metropolis of Cocoon floats high above the earth, keeping its citizens sheltered and safe from the dangers of the wilderness below. Among the populace, there are certain individuals known as I'Cie, who bear the mark of the ancient creators. This mark offers great power, but also great danger, and those who carry it are considered to be cursed. Players follow the epic adventure of a group of I'Cie, informally led by an orphan girl called Lightning, who break free from the dogmatic structures of society to bring about a new era of freedom and advancement. In the traditions of the top-selling Final Fantasy series, the game's story is told cinematically, with emotionally charged interactions between highly expressive characters, in intricately detailed computer-generated movie sequences that run between the player-controlled action.
Final Fantasy XIII uses an original variation on the "Active Time Battle" system, seen in earlier Final Fantasy games. In combat, players queue up fighting moves for their hero to attempt, limited by the number of "Command Slot" action points they have. Characters earn additional action points as they level up. Combat plays out in a real-time flow, and characters can perform their queued actions in a progression or in a custom combo burst. As players control the key character in each battle, the computer directs the attacks and defensive moves of the other heroes. Players can still influence the actions of the other allies in the fight, by using the game's "Paradigm Shift" feature to change a computer-controlled character's class type, choosing a different healing, assault, or support class. At moments of great peril, I'Cie heroes can also summon a mystical Eidolon guardian being to fight alongside them, and in certain circumstances, they can temporarily join with their summoned entities to form a powerful vehicles or weapons, using the game's "Gestalt Mode." ~ T.J. Deci, All Game Guide