Final Fantasy II is a fantasy role-playing video game developed and published by Square (now Square Enix) in 1988 for the 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, Japanese mobile phones, the Game Boy Advance, and the PlayStation Portable. Only the PlayStation, Game Boy, and PlayStation Portable versions have been released outside of Japan. As neither this game nor Final Fantasy III had been 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 release of the game is a release of the enhanced version of the game for the iOS worldwide on February 25, 2010. 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 attempt to destroy the world; the four characters agree to join forces to defeat him. They proceed to do so 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 prior 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.