senior Sega figures including Toshihiro Nagoshi and Yu Suzuki were reporting to Naka; according to Takashi Yuda, he was involved in all Sega game development. Naka announced his departure on 8 May 2006 and formed a new studio, Prope, to focus on creating original games. He left Sonic Team during the development of Sonic the Hedgehog (2006), released as part of the 15-year anniversary of the Sonic franchise. Sonic the Hedgehog was panned for its bugs and design flaws; Sonic Unleashed (2008) received mixed reviews, but sold well. Both games were released for the PlayStation 3 and Xbox 360; Sonic Team also developed a series of Sonic games for the Wii and Nintendo DS, such as 2007's Sonic and the Secret Rings. By 2010, Sonic Team had become part of CS Research and Development No. 2 (CS2), Sega Studios USA had been reintegrated into the Japanese team, and Iizuka had become the head of the department. After a series of poorly received Sonic releases, Sonic Team refocused on speed and more traditional side-scrolling in Sonic the Hedgehog 4: Episode I and II, Sonic Generations, and Sonic Colors, which all received better reviews. In 2015, Iizuka recognized in an interview with Polygon that Sonic Team had prioritized shipping games over quality, and had not had enough involvement in later third-party Sonic games, such as Sonic Boom: Rise of Lyric. He hoped the Sonic Team logo would stand as a "mark of quality"; he planned to release quality games and expand the Sonic brand, while retaining the modern Sonic design. Iizuka stated that doing new things with the franchise has good and point points at times.Sonic Team's first Sonic game exclusive to smartphones, Sonic Runners, was released in 2015. An endless runner, it was designed to have more replay value than other games in the genre. Sonic Runners received mixed reviews and was unprofitable, resulting in its discontinuation a year later. In 2017, Sonic Team developed and released Sonic Forces, and oversaw the development of Sonic Mania by Christian Whitehead. Forces was aimed at a broad audience of young and adult players, while Mania was focused on fans of the original Genesis games. Mania became the best reviewed Sonic game in fifteen years following nearly two decades of mixed reviews for the franchise. At SXSW in March 2019, Iizuka confirmed Sonic Team was also working on a new Sonic game, which became