He became the president of Polyphony Digital after designing his first game "Motor Toon Grand Prix", a cartoon-inspired racing title similar to Mario Kart. "Motor Toon Grand Prix" later spawned a sequel, "Motor Toon Grand Prix 2", which was the only game in the franchise released outside Japan. Since then, Yamauchi has fulfilled his dream of creating realistic driving simulators with his massively successful "Gran Turismo" series. He has also expressed interest in broadening out to other game genres; in 1999 Polyphony Digital released "Omega Boost", a shoot 'em up title set in space, which has since proven to be Yamauchi's only foray outside of racing game development.