Sonic CD

Sonic CD is a side-scrolling platform game similar to the original Sonic the Hedgehog (1991). Players control Sonic the Hedgehog as he ventures to stop his nemesis Doctor Robotnik from obtaining the magical Time Stones and conquering Little Planet. Like previous games, Sonic can destroy enemies and objects (such as certain walls and television monitors containing power-ups) by rolling into a ball, and collects rings as a form of health. Sonic can also perform a "spin dash" and a "super peel-out", both of which increase his speed.

Each of the seven levels are split into three zones, the third of which ends in a boss fight against Robotnik. Players start with three lives, which are lost when they suffer any type of damage without rings in their possession; losing all lives results in a game over.

At Never Lake, an extraterrestrial body, Little Planet, appears in the last month of every year. Sonic's nemesis, Dr. Robotnik, has chained the planet to a mountain and begun transforming it into a giant fortress with his robot army. To execute his plan, Robotnik uses the Time Stones, seven diamonds which control the flow of time, hidden in the different zones.

Sonic ventures to the planet, followed by the besotted Amy Rose, his self-proclaimed girlfriend. Robotnik dispatches his newest invention, Metal Sonic, to kidnap Amy at Collision Chaos, luring Sonic into danger.

The original Sonic the Hedgehog (1991) was developed by Sonic Team at Sega. It was a major commercial success and positioned Sega as Nintendo's main rival in the console market. The lead programmer, Yuji Naka, dissatisfied with Sega of Japan's rigid corporate policies, moved with several members of Sonic Team to the United States to develop Sonic the Hedgehog 2 with Sega Technical Institute (STI). Meanwhile, Sega planned to release the Sega CD add-on for its Genesis, and wanted a Sonic game that would demonstrate its more advanced features.

Naoto Ohshima, the designer of Sonic, was Sonic CD's director; the remainder of the team comprised Sega staff who had developed The Revenge of Shinobi, Golden Axe II, and Streets of Rage. The team built Sonic CD using the original Sonic the Hedgehog code as a base.

The Sega CD version sold more than 1.5 million copies, making it the system's best-seller. In the United Kingdom, it was the top-selling Mega-CD game in December 1993.

Sonic CD received acclaim. The presentation, visuals, and audio were praised. Computer and Video Games wrote that, although Sonic CD did not use the Sega CD's capabilities to its fullest, the graphics and sound were excellent, calling the music "from the likes of 2 Unlimited and Bizarre Inc". Electronic Games said that it looked similar to previous Sonic games and made minimal use of the Sega CD features, but this did not detract from the quality.

The story of Sonic CD was adapted in the twenty-fifth issue of Archie Comics' Sonic the Hedgehog comic book series. The adaptation featured some changes to the story, such as Tails being an important character and Metal Sonic having the ability to talk. The British comic Sonic the Comic also published an adaptation. The final issue of Archie's comic, #290 (December 2016), also featured a retelling of the Sonic CD story.

Two characters introduced in Sonic CD, Amy Rose and Metal Sonic, became recurring characters in the Sonic series. Metal Sonic appeared as an antagonist in Knuckles' Chaotix (1995), the Sonic the Hedgehog OVA (1996), Sonic Heroes (2003), Sonic the Hedgehog 4: Episode II (2012), and Sonic Mania (2017). Amy Rose most notably appears in Sonic Adventure (1998). The Sonic CD animated sequences were included as bonuses in the compilations Sonic Jam (1997) and Sonic Mega Collection (2002), and "Sonic Boom" was used as one of Sonic's themes in Super Smash Bros. Brawl (2008).