Final Fantasy II (ファイナルファンタジーII Fainaru Fantajī Tsū?) is a fantasy role-playing video game developed and published by Square (now Square Enix) in 1988 for Nintendo's Family Computer as the second installment of the Final Fantasy series. The game has received numerous enhanced remakes for the WonderSwan Color, the Sony PlayStation, the Game Boy Advance, the PlayStation Portable, and multiple mobile and smartphone types. As neither this game nor Final Fantasy III were initially released outside of Japan, Final Fantasy IV was originally released in North America as Final Fantasy II, so as not to confuse players. The most recent releases of the game are enhanced versions for the iOS and Android, which was released worldwide in 2010 and 2012, respectively. The game's story centers on four youths whose parents were killed during an army invasion by the empire of Palamecia. Three of the four main characters join a rebellion against the empire, embarking on missions to gain new magic and weapons, destroy enemy superweapons, and rescue leading members of the resistance. After defeating the empire and the Emperor, the trio discovers that the fourth youth, now a dark knight, has taken the place of the previous emperor and is preparing to attack the rebellion. Upon confronting him, the Emperor reappears as a demon and prepares to destroy the world. However, the four characters agree to join forces to defeat him, and ultimately they destroy him in his demonic castle. The Game Boy Advance remake adds a bonus story after the game is completed, following several side characters who died during the game as they attempt to defeat an alternate version of the Emperor. Final Fantasy II introduced many elements that would later become staples of the Final Fantasy franchise, including chocobos and the recurring character Cid. It also eliminated the traditional experience point leveling system of the previous and later games in the series, instead introducing an activity-based progression system where the characters' statistics increase according to how they are used or acquired. Despite being a sequel to Final Fantasy, the game includes no characters or locations from the first game. Final Fantasy II received little attention at the time from non-Japanese reviewers, though its remakes have garnered favorable reviews.