Sonic the Hedgehog CD/Development
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- Back to: Sonic the Hedgehog CD.
Sonic the Hedgehog CD went through many ideas and changes during the development process. What follows is a collection of items related to the game's development.
Contents
Development process
Although Yuji Naka and Hirokazu Yasuhara had gone to San Francisco to help mentor the newly-hired employees of the Sega Technical Institute and lead the development of Sonic the Hedgehog 2, Sonic creator Naoto Ohshima chose to stay behind in his native Japan, ready for his next assignment. Meanwhile, Sega of Japan, in preparation of the launch of their console add-on the Mega-CD, knew they wanted some sort of Sonic the Hedgehog title on the console to headline its existence, hoping its premier franchise would cause the new technology to be a success. At first, the company considered simply to develop an enhanced version of either the original Sonic the Hedgehog or of the upcoming Sonic 2, a practice that would shape much of the Mega-CD library in the years that followed. For one reason or another, however, it was decided that instead of porting an existing title, a new entry in the Sonic series would be developed from the ground up, which could take full advantage of the capabilities of the Mega-CD.
Once the decision was made, it didn't take long for Sega to involve Naoto Ohshima, making him the Director of the project and giving him free reign. Not wanting to make a game that was essentially the same as Sonic the Hedgehog 2, Ohshima contacted Yuji Naka and other members of the Sega Technical Institute during the initial planning stages, where both teams exchanged information about what the other wanted to do. It was during these early moments that Sonic CD started to take shape, Hiroyuki Kawaguchi becoming the art director and helping to shape the worlds of the game. Although comparisons can be made between the levels in the first Sonic the Hedgehog and its CD sequel, Kawaguchi made sure to make them visually stunning, standing out from anything that had yet been seen in the franchise.
Although the Sonic 2 team briefly considered the idea of time travel as a play mechanic, Ohshima fully embraced the concept, being in love with the idea of having the level Sonic was running in to suddenly change around him, the player instantly being warped to a different place. When time came to program the "Time Warp" sequences, however, the lead programmer Matsuhide Mizoguchi claimed that it was impossible to do such a thing on the hardware, and instead a "loading sequence" had to be created, the brief moment where Sonic can be seen flying through a green background with stars encircling him. Though Ohshima kept on pushing the programming team to find a way to circumvent this added screen (wanting the time travel to more resemble the instantaneous movement in Back to the Future), the programmers could not find a way to modify Naka's original code to create the desired effect. Years later, when Ohshima reflected back, he felt more than confident that if Naka had been the chief programmer on Sonic CD that he would have been able to find a solution, certain in his skills when it came to developing code.
Another element that Ohshima wanted to include was the expansion of Sonic's cast of characters, wanting to provide not only a new protagonist but an enemy that could be marketed on the same level as Dr. Eggman. The game's visual designer, Kazuyuki Hoshino, was tasked with creating the designs of these two new characters for the game. The first of these, Amy Rose, was actually created previously for the Sonic the Hedgehog manga. Wanting a twist on the standard kidnapping/romance scenario that had become a cliché in the gaming world, Amy was meant to be the one infatuated with Sonic, the blue hedgehog never showing any emotion back at her, his going to rescue her simply being another task to foil Eggman. The second new face in the game, Metal Sonic, was designed to be a sleek mechanical doppelgänger of the lead character, as opposed to the clunky Mecha Sonic that was drawn up for Sonic the Hedgehog 2. It may be because of this simple yet catching design, as well as his extensive use in advertising materials for the title, that allowed this robotic copy of Sonic to outlast the others.
While never mentioned in any magazine (and wouldn't be discovered until the PC port in 1996) Sonic CD did have its own collection of missing elements, much as its co-existing Mega Drive sibling. Though Sonic the Hedgehog 2's scrapped levels like Hidden Palace Zone and Desert Zone became the stuff of legend due to their extensive game journalism coverage, little is known for certain about Dubious Depths, commonly known to the Sonic-community as simply "R2". The Taxman, the developer of the 2011 remake of Sonic CD, has released concept art of Dubious Depths in the Sonic CD developer's diary, including art of the antlion enemy from the uncut extended ending video, likely meaning that the area it is found is the same round. Some enemy sprites from the round have also been shared. Before this was known, there was quite a bit of speculation as to what "R2" could have been, as the level was removed at some point before the earliest known prototype.
Though a Sonic title, the team did not receive nearly as much pressure from Sega as the team responsible for Sonic the Hedgehog 2, as Ohshima would recount:
| “ | Sonic CD wasn't Sonic 2; it was really meant to be more of a CD version of the original Sonic. I can't help but wonder, therefore, if we had more fun making CD than they did making Sonic 2 [because we didn't have the pressure of making a "numbered sequel"]. | „ |
| — Naoto Ohshima, Director of Sonic the Hedgehog CD[1] | ||
Released in Japan on September 23rd, 1993, the game would retroactively go on to be considered the killer app for the Mega-CD, even though its existence did not cause the add-on to take off as Sega had hoped.
Localization
File:SonicCD MCD US manual.pdf For the North American Sega CD release, Sega of America reworked Sonic CD's English-language story (as found in the manual) to align more closely with the branch's existing Western continuity and Saturday morning television series, such as describing Little Planet as a tiny world that orbits around Mobius and exclusively referring to the antagonist as Dr. Robotnik. However, the most infamous story localization was that of Amy Rose, who was renamed Sally Acorn in the American manual to further tie into DIC Entertainment's television series. Sega Europe's Mega-CD version retained the same broad story framework and terminology used in North America but removed the Princess Sally substitution.
The largest change made by Sega of America's management, however, is the North American version's newly composed soundtrack. Created by Spencer Nilsen and his small audio team in the span of about a month to distinguish itself from the original score's club music-heavy themes, the differing soundtracks have remained a point of contention among the Sonic fanbase.
Music and sound
Japanese and European soundtrack
Sonic the Hedgehog CD was Sega's first Sonic title to exploit the Mega-CD's ability to stream CD-DA audio rather than rely solely on the Mega Drive's FM and PSG sound hardware. According to composer Naofumi Hataya, sound director Yukifumi Makino, and other staff, the company treated the project as an opportunity to move beyond "normal" game music and aimed for music indistinguishable in quality from contemporary commercial CDs, allocating a comparatively large audio budget to do so.[2] The composers were provided advanced sound equipment like the Korg 01/W, Korg Wavestation, Roland JD-800, E-MU Systems Proteus MPS Plus Orchestral, and some Ensoniq sound cards.[3]
Following the precedent of hiring Masato Nakamura of Dreams Come True for the franchise's first two Mega Drive entries, Sega turned to Being, one of Japan's dominant music production companies at the time, to debut the series' Mega-CD outing with a pair of vocal themes. Being arranged for singer Keiko Utoku (formerly of the J-pop idol group Mi-Ke) to perform the opening and ending themes, while Casey Rankin of the Japanese pop band Shogun provided lyrics and rap parts; Rankin also brought in two session singers for early demo takes, which Hataya recalls as his first exposure to high-end professional vocal production. Portions of the in-game score were also tracked and mixed in Being's pre-production rooms, giving Sega's internal sound staff a crash course in mainstream record industry workflows.[2]
Hataya and co-composer Masafumi Ogata's early demo themes for Sonic CD were initially rejected by director Naoto Ohshima, who, in Hataya's words, was a "concept devil" and pushed them to come back with a much stronger conceptual basis rather than "close enough" songs. The turning point came when the composers reframed the entire score around the sound of early-1990s club culture. Hataya notes that Sonic had become a style icon in the United Kingdom - turntable slipmats and fashion magazines were using Sonic imagery - and that techno and house were beginning to penetrate the Japanese mainstream while already being the most familiar music to Sega's composers. From that point, they committed to building Sonic CD's soundtrack out of club music in a broad sense, using heavy dance inspirations and groove-based composition. This club-based conceptual reset was tied directly to the game's time-travel mechanic. Hataya describes how the idea of time travel informed the musical palette, using mechanical, heavily industrial textures for Robotnik's polluted Bad Futures, and more organic, "ecology"-flavored arrangements for Good Futures where nature had not been overrun.[2]
Once the club music concept was approved, Hataya re-pitched his original demo themes using sampled voices in place of a real singer, deliberately chopping them into "hiccupy" phrases to give the demo a unique sound and to reinforce the game's techno-inspired music by using sampling as a core soundtrack theme. After he laid out this conceptual framework, Ohshima approved this sample-based musical direction and allowed the team to proceed.[2] For the vocal themes "Sonic - You Can Do Anything" and "Cosmic Eternity - Believe in Yourself," the composers and Being's staff produced full studio recordings with Utoku and Rankin, using Being's professional pre-production facilities.[4] Hataya recalls this period as consisting of long days writing new tracks at Sega and nights spent commuting to Being's external studio to record them - constantly maxing out the memory of the studio's samplers as they refined their ideas. The experience reinforced for him that, once CD-DA removed most technical limits on fidelity, game music became "a pure battle of ideas," with Sonic CD acting as a formative project in teaching him the importance of rigorous conceptual design in composition.[2]
A notable structural decision was to move the Past mixes away from CD-DA audio and back into sequenced Mega Drive-based PCM. According to sound director Yukifumi Makino, the intent was to use "cheaper" sounds in the game's Past stages to evoke the atmosphere of a "prehistoric religion," contrasting sharply with the polished house and techno textures of the other time periods.[4] A December 1992 prototype build contains an earlier version of Palmtree Panic where the Past track is still stored as CD-DA audio with higher-quality instruments,[5] suggesting that the shift to sequenced Past music occurred mid-development, potentially in response to CD storage space or content-planning constraints.
List of audio sources
| Act | Composer | Audio sources |
|---|---|---|
| "Palmtree Panic" | Naofumi Hataya |
|
| "Palmtree Panic "G" mix" | Naofumi Hataya | |
| "Palmtree Panic "B" mix" | Naofumi Hataya | |
| "Collision Chaos" | Masafumi Ogata | |
| "Collision Chaos "G" mix" | Masafumi Ogata |
|
| "Collision Chaos "B" mix" | Masafumi Ogata | |
| "Tidal Tempest "G" Mix" | Masafumi Ogata |
|
| "Tidal Tempest "B" mix" | Masafumi Ogata | |
| "Quartz Quadrant "G" mix" | Naofumi Hataya |
|
| "Quartz Quadrant "B" mix" | Naofumi Hataya | |
| "Wacky Workbench" | Masafumi Ogata | |
| "Wacky Workbench "G" mix" | Masafumi Ogata |
|
| "Wacky Workbench "B" mix" | Masafumi Ogata | |
| "Stardust Speedway" | Naofumi Hataya |
|
| "Stardust Speedway "G" mix" | Naofumi Hataya | |
| "Stardust Speedway "B" mix" | Naofumi Hataya |
|
| "Metallic Madness" | Naofumi Hataya | |
| "Metallic Madness "G" mix" | Naofumi Hataya |
|
| "Metallic Madness "B" mix" | Naofumi Hataya |
|
| "Boss!!" | Naofumi Hataya |
|
| "Invincible!!" | Masafumi Ogata |
|
| "Zone Clear" | Naofumi Hataya |
|
| "Game Over" | Masafumi Ogata |
|
| "Special Stage" | Masafumi Ogata | |
| "Little Planet" | Masafumi Ogata |
|
| "Stardust Speedway "P" mix" | Naofumi Hataya |
North American soundtrack
For the North American market, Sega of America replaced the game's original music with a new soundtrack produced in-house by the company's Sega Multimedia Studio - a technologically-advanced division specializing in CD-based development - under composer and music team head Spencer Nilsen.[25][26] One of Nilsen's first projects with the studio, he recalls that Sega of America's marketing department wanted "something a little more musically rich and complex" (along with an unique vocal theme they could leverage in promoting the game), and that this difference in philosophy led to an almost complete rescore[26] - a change which management would accommodate by delaying the game's stateside release by one month, despite the NTSC version being ready for release. Despite the short timeframe, Multimedia Studio was ready for the job, boasting largely the same audio equipment as their Japanese counterparts.[3]
| “ | It was a lot of long days and nights in the studio, and because we had such a short turn-around on the project, we worked quickly and when we had something we liked, we recorded it instantly. My longtime collaborator, David Young, a fantastic musician, producer, and engineer in his own right, was so key to the success of that project, because he was able to help me write, arrange, and record on the fly, so that nothing got left behind. It’s easy to lose that important creative spark if you’re mired in technical challenges, and Dave is a very even-keeled professional, with a wicked sense of humor. When things would get too intense, Dave would crack us up with something completely obscure and hilarious. He is one of my favorite creative partners because he brings so much to the table – composing, playing, engineering, mixing – you name it and he does it well! | „ |
| — Sega Multimedia Studio composer Spencer Nilsen[26] | ||
Nilsen led the composition of the bulk of the North American stage and event music, with bassist Bobby Vega, multi-instrumentalist and producer David Young, and guitarist Erik Frykman providing key instrumentation and arrangement support.[27] In particular, Nilsen emphasizes Young's role as a technical and musical "right hand," describing how the two of them would write, arrange, and record parts on the fly to avoid losing creative momentum during a tight production schedule. He also mentions that the team often worked long days and nights to meet their already tight deadlines, with his small team tasked to recompose the game's soundtrack in about a month.[26][27] Keyboardist and synth-programmer Sterling Crew, formerly of the band Santana, was also contracted by Nilsen to provide a "different" sound, contributing several tracks for the project.[28] Santa's former percussionist Armando Peraza was also brought onboard, contributing percussion samples.[29]
The American opening and ending theme, "Sonic Boom" was composed and produced by Nilsen performed and written by the San Francisco jazz vocal trio Pastiche, consisting of Sandy Cressman, Jenny Meltzer, and Becky West.[30] Nilsen characterizes their inclusion as an experiment that worked well: with the introduction of the games' first female character Amy Rose, he felt that female voices acting as a subliminal chorus around Sonic's journey through the game would be an effective hook[26] - ultimately using Pastiche's background vocals in a number of the game's stages. Another of the game's voices, the laugh samples heard in the boss theme, were recorded by David Young's roommate at the time, an individual named Leonard DiCosimo. [3] However, due to the rushed nature of the project, a portion of the project - particularly Sterling Crew's tracks - are primarily constructed around pre-built samples, with one track (Metallic Madness) even being largely lifted from the Korg Wavestation track "New World Man".[31]
Stylistically, the North American soundtrack marks a departure from the overt club music framing of the original score and toward a more atmospheric, World music sound, with longer ambient textures and melodic motifs that lean closer to rock and fusion than to house or techno.[27] Nilsen, for his part, appreciates the original score and argues that the two soundtracks represent "completely different musical philosophies and approaches" rather than a simple case of one replacing the other, noting that both versions have attracted dedicated followings among the Sonic fanbase.[26]
Sprites
Unfinished sprites of the enemies and boss planned for Dubious Depths.
Animation concept art
Unless otherwise noted, all of the artwork shown here is by Hisashi Eguchi, the chief key animator of Sonic CD's opening and ending animations. He was in charge of animating cuts 1-9 for the opening and cuts 11, 12 and 14 for the ending. He then corrected all of the drawings done by the other animators for the rest of the cuts.
Character Model Sheets
A more finalized version of the character model sheet. Sonic has more head quills and his shoes are shaped slightly differently.
Sonic in several different action poses and Sonic standing beside an Anton badnik which can be found in the stage Palmtree Panic.
Sonic standing in a dynamic pose which bears a striking similarity to a pose used in the ending cutscene and storyboard illustrations of sonic running on water.
A reference sheet for Sonic's hands which shows various different poses and angles.
An illustration of Sonic which shows him sitting on the ground while smoking a cigarette. Presumably mounted on a staff room door as a silly welcome sign.
A cleaner version of the first picture from Sonic Generations.
Storyboards
An early storyboard for the opening animation of Sonic CD.
Key animation
Sonic standing on an elevator in Wacky Workbench.
Sonic being attacked by a Mecha-Bu badnik and the elevator Sonic is standing on is being destroyed. This scene takes place in Wacky Workbench.
Sonic standing on top of two half destroyed Mecha-Bu badniks. This scene takes place in Wacky Workbench.
Sonic in an action pose as he jumps up after ripping off the buzz-saw from a half destroyed Mecha-Bu badnik. This scene takes place in Wacky Workbench Zone.
Animation cels
Opening
Cut 5
Cut 8
Cut 8
Cut 8
Cut 8
Cut 13
Ending
Cut 7
Cut 9
Cut 9
Cut 9
Character designs
Unless otherwise noted, the images below were drawn by Kazuyuki Hoshino, character designer for Sonic CD.
Sonic the Hedgehog in a dynamic pose, which would be transformed into a sprite used in the beginning of Wacky Workbench. Scan from Sonic Generations.
Line art of Sonic that would be used for the album Sonic the Hedgehog - Remix. Scan from Sonic Generations.
Various sketches of new character Amy Rose from many angles.
A sketch of Amy Rose.
Finalized character designs of Amy and Sonic. Used as reference for the character designs in the animation.
Concept art for Amy Rose shown at the 25th anniversary party at Joypolis.
A finalized sketch of new antagonist Metal Sonic.
A character reference illustration of Metal Sonic featuring a front view, rear view, and side view profile.
An early concept sketch of Sonic and Metal Sonic for the Japanese Box Art cover, by Naoto Ohshima.
Concept art of Metal Sonic showing various angles and details of his design including a good look at different parts of his body and how they move and function.
Dr. Eggman from the front and back.
Enemy sketches
A collection of sketches of various enemies, including Tentou.
A smaller collection of enemy sketches.
A detailed look at the sketch for Poh-Bee.
A sketch of the scrapped Worm badnik intended for Dubious Depths. There is also a sign with Sonic's head on it that says "CDS" which stands for CD Sonic, the original title for the game.
An unused Burrobot variant, also intended for Dubious Depths.
Boss concepts
Dr. Eggman sitting upon the VCCI-811 "President's Chair," unused in the final game. Of note is the "Eggman Industries" logo in the upper left, also unused. Scan from Sonic Generations.
One of Eggman's alternate methods of transportation, though this model is only seen in the D.A. Garden and the "Bad Ending" animation. Scan from Sonic Generations.
An unused boss concept where Eggman sits in a wheel with a chainsaw attached to the front. The wheel theme suggests it's an earlier version of the unused R2 boss.
Initial concept art for the Eggman encounter in Metallic Madness, listed here as "Psycho Egg" from "R8." Scan from Sonic Generations.
Further sketches of Psycho Egg, looking closer to the final product, though still experimenting with how Eggman would sit within the contraption.
Miscellaneous artwork
Artwork of Little Planet and Never Lake, used in the instruction manual for the Japanese version of the game.
The familiar mountain with Eggman's face etched in. Described by Hoshino as being the background to the final stage of the game.
Detail of the Eggman mountain.
Sketches of rainbow waterfalls, intended for Dubious Depths.[32]
Ideas for neon-adorned traffic signs.
A document focusing on the Metal Sonic race in the final zone of Stardust Speedway.
Working out how the time travel mechanic would appear in the game.
Sketches of how Sonic would look running in the psudo-3D Special Stages.
A collection of Little Planet flowers, both used and unused.
Concept art for the end-of-level Signpost.
Prototype screenshots
Yuusei Sega World
Sega released a handful of screenshots of Sonic CD during the Yuusei Sega World event. The game was playable on the show floor so it was also possible for publications to take their own screenshots, however the following is thought to have come directly from Sega.
All of these images are consistent with the 1992-12-04 prototype, which is believed to have been the version playable at the event.
The "CD Sonic".
...and again
[33].
Alternative image.
It is believed Sega stitched this together, which would explain why the height of the screenshot is doubled and the camera doesn't line up. The darker, almost "gradient"-like shades in the background are a potential side effect of this trickery.
Alternative screenshot.[35]
Time monitor.[36]
The beginning of Zone 2.[35]
Alternative screenshot.
Slightly further along.
Other screenshots
Opening animation
An early first look at one of the scenes shown in the opening animation to Sonic CD. There are slight minor differences between this screenshot and the final version. The chain that holds Little Planet to the Eggman rock is missing and the reflections of Little Planet and the chain in the water is also missing.
Palmtree Panic
The first Boss with pinchers instead of bumpers, similar to the 510 prototype.
Collision Chaos
Curiously it was Collision Chaos that turned up in the gaming press first. Here we have an early version of the stage, including Anton and Mosqui enemies absent from this level in the final game.
Another screen of early Collision Chaos. The rotating platforms are circular shaped pegs instead of blue rectangle shapes as seen in the final and the background is less detailed and unfinished.[42][43]
Collision Chaos' bad future with an entirely different colour palette. The clouds, giant mountainous shrubs, neon signs, and foreground objects opt for a more bluish colour scheme, while in the final game there are reds and washed-out greens. The pipes in the background are also red, while in the final version they're green.
Tidal Tempest
The water here is higher than in the final, allowing Sonic to fall back into the lower area of the level. It's the same height as the 510 prototype.
Special Stage
An extremely early screenshot of the Special Stage, featuring not only an unused background, but yellow balloons instead of UFOs.
Later builds introduced UFOs, albeit ones with a different look to those found in the final game.
A common feature of Sonic CD prototypes are the oil slicks. While the graphics can still be found in the final version, they were removed from all stages and have no associated functionality.
Oil slicks are everywhere in prototype versions of the game, and were presumably intended to slow Sonic down.
Otherwise the level is quite similar to the final game.
Bonus Round
A single image of an unused Bonus Stage, it is unknown if it was an earlier version of the Special Stage, or if it was intended to be an extra round in addition to the Special Stage.
See also
- Sonic the Hedgehog CD prereleases - A collection of the ten known Sonic CD prototypes, and the differences between each.
External links
- Sonic CD - Developer Diary - Produced to help advertise the 2011 remake, Kazuyuki Hoshino talks about the development of the game, flipping through notebooks filled with concept art.
References
- ↑ Naoto Oshima interview by Gamasutra (December 4, 2009)
- ↑ 2.0 2.1 2.2 2.3 2.4 https://browniehideout.wordpress.com/2011/11/23/sonic-the-hedgehog-cd-original-soundtrack-20th-anniversary-edition-cd-commentary/ (Wayback Machine: 2025-07-30 20:10)
- ↑ 3.0 3.1 3.2 https://www.reddit.com/r/SonicTheHedgehog/comments/yayle8/sonic_cd_us_game_over_laugh_source
- ↑ 4.0 4.1 https://shmuplations.com/soniccd/ (Wayback Machine: 2025-09-05 22:56)
- ↑ Sonic the Hedgehog CD (Mega-CD prototype; 1992-12-04)
- ↑ 6.0 6.1 6.2 https://browniehideout.wordpress.com/2016/06/22/sonic-the-hedgehog-25th-anniversary-selection-cd-commentary/
- ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 7.10 https://docs.google.com/spreadsheets/d/1JJBlHHDc65fhZmKUGLrDTLCm6rfUU83-kbuD8Y0zU0o
- ↑ 8.0 8.1 https://www.whosampled.com/Naofumi-Hataya/Collision-Chaos/
- ↑ 9.0 9.1 https://www.whosampled.com/Naofumi-Hataya/Collision-Chaos-(Bad-Future)/
- ↑ https://www.whosampled.com/Spencer-Nilsen/Tidal-Tempest-%E2%80%9CG%E2%80%9D-Mix/
- ↑ 11.0 11.1 https://www.whosampled.com/Masafumi-Ogata/Tidal-Tempest/
- ↑ 12.0 12.1 12.2 https://www.whosampled.com/Naofumi-Hataya/Quartz-Quadrant-B-Mix/
- ↑ 13.0 13.1 https://www.whosampled.com/Naofumi-Hataya/Wacky-Workbench-(Present)/
- ↑ https://www.whosampled.com/Masafumi-Ogata/Wacky-Workbench-Good-Future/
- ↑ 15.0 15.1 https://www.whosampled.com/Masafumi-Ogata/Wacky-Workbench-B-Mix/
- ↑ 16.0 16.1 16.2 16.3 16.4 16.5 16.6 https://www.whosampled.com/Naofumi-Hataya/Stardust-Speedway-(Present)/samples/
- ↑ 17.0 17.1 https://www.whosampled.com/Naofumi-Hataya/Stardust-Speedway-Good-Future/
- ↑ 18.0 18.1 18.2 18.3 18.4 https://www.whosampled.com/Naofumi-Hataya/Stardust-Speedway-(Bad-Future)/samples/
- ↑ https://www.whosampled.com/Naofumi-Hataya/Metallic-Madness-(Present)/
- ↑ https://www.whosampled.com/Naofumi-Hataya/Metallic-Madness-(Good-Future)/
- ↑ 21.0 21.1 21.2 21.3 https://www.whosampled.com/Naofumi-Hataya/Robotnik/samples/
- ↑ @Mazin__ on X (Ghostarchive)
- ↑ https://www.whosampled.com/Naofumi-Hataya/Little-Planet/
- ↑ 24.0 24.1 https://www.whosampled.com/Naofumi-Hataya/Stardust-Speedway-(Past)/
- ↑ https://www.imore.com/gaming/for-me-sonic-cd-isnt-just-a-sequel-sonics-designer-speaks-to-imore-for-its-30th-anniversary (Wayback Machine: 2025-07-16 10:11)
- ↑ 26.0 26.1 26.2 26.3 26.4 26.5 Interview: Spencer Nilsen (2008-12-09) by Sega-16
- ↑ 27.0 27.1 27.2 https://tailschannel.com/features/analysis/sonic-cd/ (Wayback Machine: 2025-02-10 19:07)
- ↑ https://forums.sonicretro.org/threads/sonic-cd-sterling-found.27268/#post-647350 (Wayback Machine: 2025-11-25 04:49)
- ↑ http://www.salsaweb.com/music/articles/peraza_cm.htm (Wayback Machine: 2001-01-10 20:41)
- ↑ Interview: Sandy Cressman (2005-09-09) by Sega-16
- ↑ [
Sonic CD now out for everything except Nintendo consoles, post #1707 by The Taxman Sonic CD now out for everything except Nintendo consoles, post #1707 by The Taxman]
- ↑ File:DengekiMD JP 06.pdf, page 45
- ↑ 34.0 34.1 34.2 File:Famitsu JP 0212-0213.pdf, page 226
- ↑ 35.0 35.1 File:Famitsu JP 0212-0213.pdf, page 227
- ↑ File:DengekiMD JP 08.pdf, page 45
- ↑ File:DengekiMD JP 03.pdf, page 149
- ↑ 38.0 38.1 File:DengekiMD JP 03.pdf, page 45
- ↑ File:DengekiMD JP 07.pdf, page 45
- ↑ File:DengekiMD JP 05.pdf, page 45
- ↑ File:DengekiMD JP 04.pdf, page 45
- ↑ File:SegaForce UK 16.pdf, page 12
- ↑ File:GameFan US 0107.pdf, page 44
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