From Sonic Retro

The Sonic the Hedgehog series primarily consists of video games owned and published by Sega, starring its corporate mascot, Sonic the Hedgehog. The series began with the release of Sonic the Hedgehog on the Sega Mega Drive in 1991, whose success led to over fifty further video games featuring Sonic and his friends in the decades which followed.

The world of Sonic typically sees the titular blue hedgehog attempting to thwart the villainous Doctor Eggman and his evil schemes, typically ranging from converting the local populace into robots, or to conquer the world through some diabolical means. Sonic's speed and quick wits usually gets the better of Eggman, and he is often joined by friends such as Miles "Tails" Prower, Amy Rose and Knuckles the Echidna, among others.

Sonic games are typically action platformers, initally 2D, but moving into the third dimension as technology progressed through the second half of the 1990s. He has, however, appeared in games of all genres, including puzzle, racing and even RPGs, for a wide variety of consoles and computers from 1991 to the present day. In total more than 150 million units have been sold, making Sonic one of the best selling video game franchises of all time.