Sonic the Hedgehog

The Sonic series is characterized by speed-based platforming gameplay. Controlling the player character, the player navigates a series of levels at high speeds while jumping between platforms, fighting enemies and bosses, and avoiding obstacles. The series contains both 2D and 3D games. 2D entries generally feature simple, pinball-like gameplay—with jumping and attacking controlled by a single button—and branching level paths that require memorization to maintain speed.

Meanwhile, 3D entries tend to be more linear in design, feature various level objectives, different movesets, and allow players to upgrade and customize the playable character. Games since Sonic Unleashed have blended 2D and 3D gameplay, with the camera shifting between side-scrolling and third-person perspectives.

By 1990, the Japanese video game company Sega wanted a foothold in the video game console market with its 16-bit console, the Sega Genesis. Sega's efforts had been stymied by the dominance of Nintendo; the Genesis did not have a large install base and Nintendo did not take Sega seriously as a competitor. Sega of America CEO Michael Katz attempted to challenge Nintendo with the "Genesis does what Nintendon't" marketing campaign and by collaborating with athletes and celebrities to create games. These efforts did not break Nintendo's dominance, and Katz was replaced by Tom Kalinske, formerly of Mattel.

Sega president Hayao Nakayama decided Sega needed a flagship series and mascot to compete with Nintendo's Mario franchise. Nintendo had recently released Super Mario Bros. 3, at the time the bestselling video game ever. Sega's strategy had been based on porting its successful arcade games to the Genesis; however, Nakayama recognized that Sega needed a star character in a game that could demonstrate the power of the Genesis's hardware.

The Sonic platformers released during the 1990s were acclaimed and have been listed among the greatest video games of all time. The original Sonic was touted as a faster, cooler alternative to Nintendo's Super Mario World (1990). According to Kotaku's Zolani Stewart, Sonic's rebellious character was representative of the culture of the 1990s, "when the idea of individual rebellion seemed inextricably linked to consumer culture". Writing in The Guardian, Keith Stuart observed that Sonic the Hedgehog's emphasis on speed departed from accepted precepts of game design, requiring that players "learn through repetition rather than observation" as "the levels aren't designed to be seen or even understood in one playthrough...

Sonic is incorrect game design and yet ... it's a masterpiece." Sonic 2, Sonic CD, Sonic 3, and Sonic & Knuckles were praised for building on the first game's formula; in 1996, Next Generation described them as "the zeitgeist of the 16-bit era".