Sonic the Hedgehog is the title character and the protagonist of the Sonic the Hedgehog video game series published by Sega, as well as numerous spin-off comics, animations, and other media. Sonic is a blue anthropomorphic hedgehog who can run at supersonic speeds and curl into a ball, primarily to attack enemies. In most games, Sonic must race through levels, collecting power-up rings and avoiding obstacles and enemies. Programmer Yuji Naka and artist Naoto Ohshima are generally credited with creating Sonic. Most of the games are developed by Sonic Team. The original Sonic the Hedgehog (1991) was released to provide Sega with a mascot to rival Nintendos flagship character Mario. Sonic was redesigned by Yuji Uekawa for Sonic Adventure (1998), with a more mature look designed to appeal to older players. Sonic is one of the worlds best-known video game characters and a gaming icon. His series had sold more than 80 million copies by 2011. In 2005, Sonic was one of the first game character inductees into the Walk of Game alongside Mario, Link, and Master Chief. Sonics first shown appearance in a video game was in the 1991 arcade racing game Rad Mobile, as a decorative ornament hanging from a rearview mirror. Sonics first playable appearance was in the platform game Sonic the Hedgehog for the Sega Mega Drive/Genesis, which also introduced his nemesis Dr. Robotnik. His two-tailed fox friend Tails joined him in the games 1992 sequel, Sonic the Hedgehog 2. Sonic CD, released in 1993, introduced Sonics self-appointed girlfriend Amy Rose and recurring robotic doppelgänger Metal Sonic as Sonic traveled through time to ensure a good future for the world. Sonic 3 and its direct sequel Sonic & Knuckles, both released in 1994, saw Sonic and Tails battle Robotnik again, with the additional threat of Knuckles, who is tricked by Robotnik into thinking Sonic is a threat. Sonic 4 (2010–2012) continues where the story of Sonic 3 left off, reducing Sonic to the only playable character and releasing in episodic installments. The second episode sees the return of both Tails as Sonics sidekick and Metal Sonic as a recurring enemy. Other two-dimensional platformers starring Sonic include Sonic Chaos (1993), Sonic Triple Trouble (1994), Sonic Blast (1996), Sonic the Hedgehog Pocket Adventure (1999), Sonic Advance (2001), Sonic Advance 2 (2002), Sonic Advance 3 (2004), Sonic Rush (2005), Sonic Rush Adventure (2007), Sonic Colors (2010), and Sonic Generations (2011), all in which were released for handheld consoles. Sonic Adventure (1998) was Sonic Teams return to the character for a major game. It featured Sonic returning from vacation to find the city of Station Square under attack by a new foe named Chaos, under the control of Dr. Robotnik (now known as Dr. Eggman). It was also the first Sonic game to feature a complete voice-over. Sonic Adventure 2 (2001) placed Sonic on-the-run from the military (G.U.N.) after being mi