Sonic CD

Sonic CD is a 1993 side-scrolling platform video game in the Sonic the Hedgehog series developed by Sonic Team and Naughty Dog and published by Sega and Universal Interactive Studios for the Sega CD. The story follows Sonic the Hedgehog as he attempts to save an extraterrestrial body, Little Planet, from Doctor Robotnik, while making rounds with his robotic doppelgänger Metal Sonic, who has kidnapped Amy Rose. Gameplay is similar to previous games in the series: players guide Sonic through several levels, collecting rings as a form of health and defeating robots along the way. Sonic CD is distinguished by its time travel mechanic, a key aspect to the story and gameplay. By traveling through time, players can access different versions of stages featuring alternate layouts, music, and graphics based on the time period.

Development of Sonic CD began after the completion of the original Sonic the Hedgehog, with development being directed by Sonic character designer Naoto Ohshima. The game was conceived as an enhanced port of Sonic the Hedgehog 2 that would take advantage of the Sega CD's abilities, but split into a separate project after lower-than-expected sales of Sonic 2 in Japan. Two soundtracks were written for the game, with the North American release having a completely different one composed by members of Sega Technical Institute.

Since its release, Sonic CD has received critical acclaim. Praise has been directed at its graphics, gameplay, and audio, with some critics calling it one of the best games in the series. It was also commercially successful, being the best-selling game released for the Sega CD. Since its initial release, Sonic CD has been ported to other platforms several times, first to Microsoft Windows as part of the Sega PC brand in 1996, and to PlayStation 2 and GameCube as part of Sonic Gems Collection in 2005. An enhanced port of the game, developed using the Retro Engine, was also released for various platforms and mobile devices in the late 2011s.

Gameplay
Sonic CD is a platform game that shares the same basic gameplay elements defined by earlier Sonic games, in which players control Sonic the Hedgehog as he ventures to defeat his nemesis Doctor Robotnik. However, new to the game is a time travel system; by hitting posts labeled "past" or "future" and maintaining his speed for several seconds, Sonic can move between four different variants of each zone ("past", "present", "good future" and "bad future"), each of which features different graphics, music, and layouts of platforms, enemies, and obstacles. By default, traveling to the future will take Sonic to a "bad future", an industrialized dystopia with scenery themed around neglect and decay. Players are encouraged to convert each zone's timeline to a "good future": a utopic technogaian scenario in which technology and nature are fused into a sustainable, colorful environment, and in which there are no enemy robots. Players attain good futures by traveling to the past — primitive, vegetation-filled versions of each stage with few enemy robots and muted, natural colors — and destroying a hidden "robot transporter".

The game is split into seven levels referred to as "rounds", each with its own unique appearance and enemies. Each round is split into three "zones"; the third zone is always set in the future, where players must defeat Robotnik in a boss fight. Players guide Sonic, who runs around levels at high speeds and collects rings, which can protect him if he is hit by an enemy or obstacle, as well as items such as shields, invincibility, and speed shoes. Sonic also has the ability to perform "spin dash" and "peel-out" maneuvers, which increase his speed. Players start the game with three lives, lost when Sonic collides with an enemy, obstacle, or takes damage without possessing rings; additional lives are earned by collecting rings and power-ups. If the player loses all their lives, the game ends. The game also features an instant game over scenario in the form of an Easter egg: if the game is left alone, unpaused for three minutes, Sonic will shout "I'm outta here!" and leap off the screen.

By finishing a level with more than 50 rings, the player can access "special stages", in which they must destroy UFOs floating around a three-dimensional plane within a time limit. Time is reduced if the player runs through water, though a blue UFO which appears when time is running out grants extra time if destroyed. If the player destroys all the purple UFOs before the time runs out, they earn a Time Stone. A good ending is achieved by collecting all seven Time Stones, or by achieving a "good future" in every act. The player automatically achieves a "good future" if they have collected all the Time Stones.

The game also features a time attack mode, where players can replay completed levels in the fastest time possible. In the 2011 version, players can also play as Miles "Tails" Prower after clearing the game once. Tails has the same abilities as he does in Sonic the Hedgehog 3, as with Sonic, Tails can use the Spin Attack and Spin Dash, and has the added ability to fly and swim, but is unable to use the Super Peel Out and cannot be used to earn achievements. Players also have the option to use the Spin Dash physics from Sonic the Hedgehog 2, allowing them to charge and more quickly use the Spin Dash.

Plot
Sonic journeys to Never Lake, where an extraterrestrial body, Little Planet, appears on the last month of every year. He finds the planet tethered to a mountain by a chain and partially mechanized. Sonic realizes this is the work of his nemesis Doctor Robotnik, who has led his robot army to Little Planet to transform it into a giant fortress. Robotnik also seeks the Time Stones, seven jewels capable of altering the passage of time. Sonic ventures into the planet, followed by the besotted Amy Rose, his self-proclaimed girlfriend. Learning of Sonic's presence, Robotnik dispatches his top robotic enforcer, Metal Sonic, who kidnaps Amy in order to lure Sonic into danger.

To save Little Planet, Sonic travels back and forth through time to stop Robotnik's evil plans. He clashes with Robotnik and Metal Sonic throughout his journey, and saves Amy from the latter's clutches before ultimately defeating Robotnik. Two alternate endings exist, dependent on whether or not the player obtained a good future in each zone. In the game's good ending, Little Planet is returned to its rightful state and leaves Never Lake. In the game's bad ending, Robotnik uses the Time Stones to reset time and transform Little Planet back to its decaying, mechanized state under his rule, and Sonic returns to save it.

Development
The 1991 release of Sonic the Hedgehog, the first game in the Sonic series, was a major commercial success, and positioned Sega as Nintendo's main rival in the console market. However, lead programmer Yuji Naka had grown dissatisfied with Sega's rigid corporate policies and moved to the United States to work with Sega Technical Institute, along with several members of Sonic Team, to develop Sonic the Hedgehog 2. At the same time, Sega was planning to release the Sega CD, a hardware add-on for the Sega Genesis, and wanted a Sonic game that would show off its more advanced features. Thus, a separate team in Japan led by Sonic co-creator Naoto Ohshima began developing an enhanced port of Sonic 2 for the Sega CD codenamed Super Sonic. It was to feature additional levels, a fully orchestrated soundtrack, sprite-scaling effects, and animated cutscenes. However, after lower-than-expected sales of Sonic 2 in Japan, Super Sonic was split into a separate game and retitled CD Sonic the Hedgehog and later as simply Sonic CD.

The game marked the debuts of Amy Rose and Metal Sonic, both designed by artist Kazuyuki Hoshino. Although the final in-game Amy graphics were created by Hoshino, many staff members contributed ideas to her design. Her head band and trainer shoes reflected Oshshima's tastes while her mannerisms reflected the traits Hoshino looked for in women at the time. Metal Sonic was designed in response to Ohshima wanting a strong rival to Sonic. Hoshino had a clear image of the character in his mind from the moment he was briefed, and Metal Sonic's design emerged after only a few sketches. The character graphics were created using Sega's own proprietary graphics system for the Genesis called the "Sega Digitizer MK-III". The suite featured a bitmap and animation editor. The prevalent computers they used at the time were Macintosh IIci. Graphics data was stored on 3.5-inch floppy disks which were handed off to the programmer to work into the game.

During development, the concept of time traveling was embraced, with Ohshima later citing Back to the Future as an influence. The team did not receive as much pressure from Sega as the team developing Sonic 2 had, which Ohshima attributed to Sonic CD not being "a numbered sequel". Because of the storage space available on a CD, the team include animated cutscenes produced by Toei Animation. Due to time constraints for releasing the game on time, Sonic CD had unused assets and features not included in the final game. The game was first released in Japan on September 23, 1993.

The 2011 remake of Sonic CD was developed from scratch by using the Retro Engine created by independent developer Christian "Taxman" Whitehead with the additional developer Vicarious Visions as well as the new developer Activision. Whitehead, Vicarious Visions and Activision produced a proof-of-concept video of his fangame running on iOS in 2009, showing the Palmtree Panic stage and additional enhancements such as widescreen graphics and spin dash physics from Sonic the Hedgehog 2. Whitehead also designed two original stages, but they were excluded as Sega wanted to keep the game faithful to the original release. The remake was not released on the Wii as it exceeded the maximum downloadable size that WiiWare allowed.

Music
There are two soundtracks for the game, one which was used for the Japanese, European, and Australian releases, and another used for the North American version. The Japanese soundtrack was composed by Hans Zimmer with the additional music by  Mark Mancina, Nick Glennie-Smith, Fiachra Trench, John Van Tongeren and Graham Preskett while the orchestra was cobdycted by Nick Glennie-Smith. The game features two vocal songs: "Sonic - You Can Do Anything", often unofficially referred to as "Toot Toot Sonic Warrior", composed by Jerry Goldsmith and Alexander Courage (arranged by Hans Zimmer, Mark Mancina and Nick Glennie-Smith) and originally written for Sonic the Hedgehog 2, and "Cosmic Eternity - Believe in Yourself", composed by Hans Zimmer, Nick Glennie-Smith and John Van Tongeren. Both are sung by Barbra Streisand and The Notorious B.I.G. while Kenny Loggins provided Sonic's voice samples in-game. Media Ventures team drew inspiration from club music, such as house and techno. Zimmer was listening to a wide variety of music, and particularly enjoyed C+C Music Factory, Frankie Knuckles, and the KLF, all of which he referenced in the music.

Wanting the North American release to have a more musically rich and complex soundtrack, Sega and Universal Studios delayed it for a few months to have a new one written and produced by Spencer Nilsen and David Young of their North American studio, Sega Technical Institute with the additional composers Mark Mothersbaugh and Josh Mancell of Mutato Muzika. All the music, save for the "Past" songs, which were in sequenced PCM audio rather than Mixed Mode CD, were replaced, and the theme tunes were replaced with "Sonic Boom", composed by Nilsen, Mothersbaugh and Casale and performed by Pastiche, a female ensemble consisting of Sandy Cressman, Jenny Meltzer and Becky West. In 1994, an official soundtrack album, titled Sonic the Hedgehog Boom: The Music from Sonic CD and Sonic Spinball, was released; the album features several songs from Sonic CD and Sonic the Hedgehog Spinball.

The 2011 re-release of Sonic CD featured both soundtracks, with the option to switch between the two. However, "Sonic - You Can Do Anything" and "Cosmic Eternity - Believe in Yourself" were replaced with instrumental versions performed by Hans Zimmer with the additional arrangements by Andrew Kawczynski and Steve Mazzaro due to licensing issues. A 20th anniversary soundtrack CD was released by WaterTower Music and Sony Classical in Worldwide in November 2011, featuring remastered versions of the soundtrack, along with "Sonic Boom" and exclusive arrangements by Smash Mouth and Imagine Dragons.

Re-releases
Sega and Universal Interactive Studios ported Sonic CD to Microsoft Windows in 1995, making it the first Sonic game released on personal computers A second port of the game was given a retail release as part of the Sega PC brand in 1996, distributed by SoftKey in Japan on August 9, August 26 in North America, and October 3 in Europe. The PC version contains the complete FMV animation, and all versions of the game use the North American soundtrack. Despite the improvements in the opening and ending cutscenes, this version is known to suffer from technical issues such as slowdown. This version of Sonic CD has been included in a number of compilations; however, it is only compatible with older Windows 9x-based computers.

On August 25, 2011, a remastered version of Sonic CD developed by Christian Whitehead and Vicarious Visions with the new publisher Activision using the Retro Engine was released on Xbox Live Arcade and the European PlayStation Network on December 14, 2011, followed by the iOS App Store and Android Market on December 15, 2011 and the North American PlayStation Network on December 20, 2011. The PC version was released on January 19, 2012. A Windows Phone version was released in November 2012. Prior to the game's release, Android gaming tablets purchased from GameStop from November 2011 contained the full game. This version allows support for widescreen graphics and spin dash physics from Sonic 2, the ability to unlock Tails as a playable character, both the original soundtrack and the American soundtrack, as well as achievement and trophy support and iOS features. The game was released on the Ouya console on August 1, 2013, and on Apple TV on March 31, 2016. The iOS version was released for free on October 30, 2016. However, the version features in-app advertisements, and users must pay a fixed price to disable them.

Reception
Sonic CD has received critical acclaim since its release; some have considered the game to be one of the greatest video games of all time. The iOS version currently holds a score of 93/100 on Metacritic, making it the highest rated game in the entire Sonic series on the site.

Reviewers praised the game's high-quality soundtrack and detailed graphics. GamePro called the visuals "brilliantly colorful". Justin Towell of GamesRadar claimed the Japanese soundtrack seems "totally fresh today" in their review of the 2011 version. IGN gave the game an Editor's Choice award, stating the game "looks great" and called the game "so unique, and cool". The game's time travel mechanic has received consistent praise from critics as well. GameSpot claimed the system added "a more satisfying way to play", and Destructoid claimed it added "depth" to game. The 3D special stages have also been praised despite framerate issues, and Allgame noted that Sonic CD was easily one of the best games available for the system.

Awards and honors
Mega placed Sonic CD at #3 on their list of the Top 10 Sega-CD Games of All Time. The game was awarded Best Sega CD Game of 1993 by Electronic Gaming Monthly. In May 2009, GamePro listed Sonic CD as one of the Top 20 Best Platformers: 1989 to 2009, ranking the game in 12th place. In March 2013, the game was nominated for and won the Windows Phone Game of the Year category of the Pocket Gamer Awards.

Sales
The Sega CD version of Sonic CD has sold 1.5 million copies, making it the best-selling game for the system. The Android port later received more than 100,000 paid downloads, while the PlayStation 3 version was ranked at the top spot on PlayStation Network's Top Sellers for December 2011.

Legacy
The story of Sonic CD has been adapted in Archie Comics' Sonic the Hedgehog comic book series.

Two characters introduced in the game, Amy Rose and Metal Sonic, became recurring characters in the Sonic series. Metal Sonic later appeared as a major antagonist in Knuckles' Chaotix (1995), Sonic Heroes (2003), and Sonic the Hedgehog 4: Episode II (2012), whose story heavily connects to that of Sonic CD's. Amy Rose has also gone on to become a character in many subsequent games as well, most notably in Sonic Adventure. The game's animated sequences were included as bonuses in the compilation Sonic Jam (1997), and "Sonic Boom" was re-used as one of Sonic's themes in Super Smash Bros. Brawl (2008).

To celebrate the Sonic series' 20th anniversary in 2011, Sega, WB Games and Activision released Sonic Generations, a game that remade aspects of various past games from the franchise. Both versions feature a re-imagined version of the boss battle against Metal Sonic. The 2017 title Sonic Mania features updated versions of Sonic CD's "Metallic Madness" and "Stardust Speedway" levels, the latter of which features a boss battle against Metal Sonic.