gang of rebellious inline skaters, is cited as a major example of Sega's commitment to original concepts during the Dreamcast's lifespan. Jet Set Radio also popularized cel shaded graphics, though it failed to meet Sega's sales expectations. The role-playing game Skies of Arcadia, developed by Overworks and produced by Rieko Kodama, was acclaimed for its surreal Jules Verne-inspired fantasy world of floating islands and sky pirates, charming protagonists, exciting airship battles and memorable plot. AM2 developed what Sega hoped would be the Dreamcast's killer app, Shenmue, a "revenge epic in the tradition of Chinese cinema", with a level of detail considered unprecedented for a video game. Incorporating a simulated day-and-night cycle with variable weather, non-player characters with regular schedules, the ability to pick up and examine detailed objects, and introducing the quick-time event in its modern form, Shenmue went over budget and was rumored to have cost Sega over $50 million. According to Moore, Shenmue sold "extremely well", but had no chance of making a profit due to the Dreamcast's limited installed base. Visual Concepts' NFL 2K football series and its NBA 2K basketball series were critically acclaimed. NFL 2K was considered an outstanding launch game for its high-quality visuals and "insightful, context-friendly, and, yes, even funny commentary", while NFL 2K1 featured groundbreaking online multiplayer earlier than its chief competitor, EA's Madden NFL series. Madden and 2K continued to compete on other platforms through 2004, with the 2K series introducing innovations such as a first person perspective new to the genre, and eventually launching ESPN NFL 2K5 at the aggressively low price point of $19.95 until EA signed an exclusive agreement with the National Football League, effectively putting every other pro-football game out of business. After Sega sold Visual Concepts for $24 million in 2005, the NBA 2K series continued with publisher Take-Two Interactive. During the Dreamcast's lifespan, Visual Concepts also collaborated with the Sonic the Hedgehog level designer Hirokazu Yasuhara on the action-adventure game Floigan Bros. and developed the action game Ooga Booga. Ports and third-party games Before the launch of the Dreamcast in Japan, Sega announced its NAOMI arcade board, a cheaper alternative to the Sega Model 3. NAOMI shares the same technology as the Dreamcast, with twice as much system, video, and audio memory and a 160 MB flash ROM board in place of a GD-ROM drive, allowing nearly identical home conversions of arcade games. Games were