and produced by longtime series contributors Takashi Iizuka and Yuji Naka respectively. Development began shortly after the release of the American version of Sonic Adventure in September 1999, and lasted 18 months. It was designed to be more action-oriented than the slower, more story-based Adventure. The development team ran the game at 60 frames per second with "tempo", giving Sonic a variety of actions rather than focusing on speed alone. Its levels facilitated this flow, making Sonic seem faster. All six playable characters have roughly equal gameplay time (unlike Adventure, in which some characters had short stories). The levels and environments were inspired by San Francisco, where Sonic Team had its office, and other American locations, such as Yosemite National Park (where the team vacationed) and the San Francisco Bay Area. Compared to Adventure, the sequel was intended to have "more of an American flavor". Although the level design prioritized the frame rate, it was more streamlined than Adventure because of the team's experience with Dreamcast hardware. Whereas Sonic Team had tried to include as much content as possible in Sonic Adventure, for the sequel they only concentrated on the elements they deemed necessary. Naka said Sonic Adventure 2 was also easier to develop, as Sonic Team could now "tap the full power of the console and deliver a much better experience". Iizuka described the Chao as a "relative neutral entity" in Sonic Adventure. In the sequel, the developers expanded their presence, adding the ability to raise "Hero" and "Dark" Chao to reflect the conflict between good and evil. Chao have the ability to socialize, so they resemble a "real artificial life form". Sonic Team showcased Sonic Adventure 2 with a trailer at E3 2000, and uploaded the trailer to its website on June 30. Sonic Team posted a trailer and a number of screenshots on May 30, 2001, with Sega promoting Sonic Adventure 2 as the last Sonic game for the Dreamcast and as marking the series' 10th anniversary. Sega held a 10th-anniversary party for Sonic in June 2001, at which attendees could compete in a battle tournament; the winner played against Iizuka. Music As with Sonic Adventure, Jun Senoue served as sound director and lead composer. Additional music was contributed by Fumie Kumatani, Tomoya Ohtani, and Kenichi Tokoi. The soundtrack is primarily melodic rock, with some hip hop and orchestral tracks. As in Adventure, each character has a