Square Enix made official announcement some details of Theatrhythm Final Fantasy for 3DS and the official site is up too! Cover from Final Fantasy 1 to Final Fantasy XIII. Each title has three stages: "field," "battle" and "event", each of these stages has different gameplay systems and difficulty. After each stage characters will level up, and players can also unlock music and movies for their collection.
On the music front, the game will have major songs from the numbered FF games. Specific songs mentioned by Square Enix include Clash on the Big Bridge (Final Fantasy V), One Winged Angel (Final Fantasy VII), At Zanarkand (Final Fantasy X) and The Sunleth Waterscape (Final Fantasy XIII). And, of course, the main FF theme.