Sonic the Hedgehog 2 (Japanese: ソニック・ザ・ヘッジホッグ2, Hepburn: Sonikku za Hejjihoggu Tsū) is a platform video game developed by Sonic Team and Sega Technical Institute, and published by Sega for the Sega Mega Drive/Genesis console. It was released in Japan on November 21, 1992 and in North American and European markets on November 24 the same year. The game is an installment in the Sonic the Hedgehog series, and focuses on the protagonist Sonic the Hedgehog and his friend, a fox named Miles "Tails" Prower, who must stop the series antagonist Dr. Ivo Robotnik from stealing the Chaos Emeralds to power his Death Egg space station.Development of the game began in November 1991, two months later than originally intended, because Sega of America initially felt that it was too soon for a sequel. Both the American and Japanese Sonic Team staff contributed to developing the game; art director Tim Skelly designed the appearance of the game's new 3D Special Stages, which were based on an earlier tech demo created by Yuji Naka. The staff increased the speed of Sonic the Hedgehog 2 in comparison to its predecessor. As with the first installment, the soundtrack was composed by Masato Nakamura.The game was a critical and commercial success upon release, with critics praising it for building upon the original Sonic the Hedgehog game. The game has sold over 6 million copies, making it the second-best-selling game on the console, behind only its predecessor in the Sonic series. Since its initial release, the game has been released in several compilations and download releases for various platforms, which were also generally positively received.