Square Enix's and Disney's Kingdom Hearts series of video games takes place in an unnamed outer space-like fictional universe with numerous self-contained worlds to explore over the course of play. Many of these worlds are based on animated Disney movies, though Kingdom Hearts II introduced some worlds based on live action Disney films. In addition to the Disney worlds, Square included original worlds over the course of the series. The concept of the games and setting was developed by Tetsuya Nomura, the series' director. The series centers around the main character Sora's search for his friends and his encounters with Disney and Final Fantasy characters on their worlds. The first game, Kingdom Hearts, takes him through each world to lock their keyholes and prevent the Heartless from destroying them. In the Game Boy Advance sequel Kingdom Hearts: Chain of Memories, taking place in Castle Oblivion, he revisits memory based versions of many of these worlds. In Kingdom Hearts II, Sora helps the residents of these worlds again in search of his friend Riku. The Kingdom Hearts games have been both critically acclaimed and commercially successful. The worlds used in the games have received praise from reviewers.
The universe of Kingdom Hearts is a collection of various levels, referred to as "worlds", that the player progresses through. Each world varies in appearance and setting, depending on the Disney world that it is based on; graphics of the worlds and characters resemble the art style from their respective Disney film. Disney worlds are inhabited by characters from their respective Disney film; Hercules and Philoctetes inhabit Olympus Coliseum, and Aladdin, Princess Jasmine, and the Magic Carpet inhabit Agrabah. Worlds are disconnected from each other and with a few exceptions, most characters in the worlds are unaware of the existence of the other worlds. Worlds are made up of interconnected field maps where battles and events take place. Players travel from one world to another via a Gummi Ship. The worlds created specifically for the game mirror the overall appearance of the other worlds and feature either new characters or characters from several Final Fantasy games.