History VideoGame / SonicTheHedgehogCD

** If the timer is running low in a Special Stage, the game will automatically spawn an extra UFO that adds 30 extra seconds to the timer. And if you destroy it, but time runs low again, it will respawn and let you destroy it again for another time boost. As an extra mercy, you ''don't'' have to destroy this extra UFO to win the Time Stone either.

** There's one in the Present stage of Stardust Speedway Zone 1 right before the end of the level. However, it's almost impossible to get down there and even if you do, there is still a way back up. You have to deliberately kill yourself to fall into that pit. There's also one in the Past of Stardust Speedway Zone 2. Like the example mentioned above, there is a short wall and spring blocking the drop, meaning you have to ''try'' to fall down there.

** Due to the sheer complexity of the Time Travel sidequest, the game has a save feature that autosaves after completing a world.
** If you execute a time warp while the timer is at more than 5 minutes [[TimedMission out of 10]], the timer will reset back to the 5'00"00 mark. This feature is missing in the 2011 remaster, however.

** If the timer is running low in a Special Stage, the game will automatically spawn an extra UFO that adds 30 extra seconds to the timer. And if you destroy it, but time runs low again, it will respawn and let you destroy it again for another time boost. As an extra mercy, you ''don't'' have to destroy this extra UFO to win the Time Stone either.
** Getting all seven Time Stones automatically grants you a Good Future in each Zone and the Good Ending, meaning a player doesn't have to waste extra time trying to find the remaining robot teleporters, which will already be destroyed.

** In the ''Sonic Origins'' version of the game, restarting a level outside of Act 3 will have Sonic or Tails remain in their current time zone, which is useful if either miss any machines in the past or need another go at time-travelling if the time posts have already been used. Any already-destroyed machines will also remain destroyed if you do this.

** Many zones have at least one Past sign located close to some sort of stage gimmick that allows for easy time-travel. The most common is simply two springs facing one another, ricocheting you back and forth until you time-travel, though most stages have their own specific gimmicks that allow for this.
** While time travel is normally pretty difficult, due to having to run at full speed for around 30 seconds without stopping or running into anything, there are a few locations with two springs facing opposite directions, allowing Sonic to just bounce back and forth until the time travel activates. There are a few other level gimmicks that similarly allow easy time travel, such as these weird spinning things in the Wacky Workbench zone. All you have to do is hit a time travel post, then jump inside.

''Sonic the Hedgehog CD'' (also known as ''Sonic CD'') is a ''Franchise/SonicTheHedgehog'' game released for the UsefulNotes/SegaCD in 1993 as a direct sequel to [[VideoGame/SonicTheHedgehog1 the original 1991 game]]. While it was released after ''VideoGame/SonicTheHedgehog2'', the games were developed in tandem, and as a result, have some notable differences between them; the CompilationRerelease ''Sonic Origins'' would later definitively confirm that ''CD'' takes place before ''Sonic 2'', helping explain at least a few of the discrepancies. This game introduced two {{Breakout Character}}s: Sonic's pink {{fangirl}} Amy Rose, and his definitive EvilKnockoff Metal Sonic. The [[PreRenderedGraphics animated opening and ending sequences]] were done by Creator/StudioJunio and Creator/ToeiAnimation.

The original version of the game was ported to the [[UsefulNotes/IBMPersonalComputer PC]] in 1996, and was later included in the ''Sonic Gems Collection'' [[CompilationRerelease compilation]] in 2005 for the UsefulNotes/PlayStation2 and UsefulNotes/NintendoGameCube. It was excluded from ''Sonic'' compilations for several years due to Sega losing the documentation for the Sega CD -- the ''Gems Collection'' port is based on the PC version.

To address this issue, the game was [[VideoGameRemake remade]] from scratch in 2011, using the Retro Engine [[https://www.youtube.com/watch?v=EJa-4tMqVNc developed]] by PromotedFanboy Christian "The Taxman" Whitehead. It was released on UsefulNotes/{{Xbox 360}} through UsefulNotes/XboxLive, UsefulNotes/PlayStation3 through the UsefulNotes/{{PlayStation Network}}, PC through UsefulNotes/{{Steam}}, UsefulNotes/{{Android|Games}} and UsefulNotes/{{iOS|Games}} devices, and Windows Phone. [[labelnote:''Phew!'']]The phone version was announced with the others but not released until November 2012 alongside Windows Phone 8.[[/labelnote]]

* TakeThat: [[AllThereInTheManual The name of the first boss]] is the EGG-HVC-001. HVC-001 was the model number of Creator/{{Nintendo}}'s own [[UsefulNotes/NintendoEntertainmentSystem Famicom]] console: the HVC stands for "Home Video Computer". As a bonus stealth insult, the HVC-001 [[WarmUpBoss is the easiest boss in the entire game]]. Fighting it in the Good Future also colors it pink, and this is probably the only explanation for that.

*** Collision Chaos has a [[JustForPun Spring Yard]] at the end of both Zones 1 and 2. The second zone also has two goals, just like the Act 2 of its original counterpart.

** The 2011 Retro Engine remaster features native widescreen resolution, runs at 60 FPS across the board (even during the Special Stages), has the highest quality [=FMVs=] over prior releases, added the ability to use ''Sonic the Hedgehog 2''[='=]s Spin Dash mechanics while keeping the original as an option, revamped the game's save feature, has both the North American and Japanese soundtracks, and added Tails as a unlockable playable character. This version is the one that serves as the basis for the version in ''Origins'' (and the ''plus'') expansion, with ''Origins'' making a few new changes from the 2011 port, most notably adding the Drop Dash to Sonic's moveset, Tails being playable from the start, and the ''Origins Plus'' DLC adding in Knuckles and Amy as playable characters (also adding in a few Knuckles-specific routes to certain Zones).

** The 2011 Retro Engine remaster features native widescreen resolution, runs at 60 FPS across the board (even during the Special Stages), has the highest quality [=FMVs=] over prior releases, added the ability to use ''Sonic the Hedgehog 2''[='=]s Spin Dash mechanics while keeping the original as an option, revamped the game's save feature, has both the North American and Japanese soundtracks, and added Tails as a unlockable playable character.

* TimeTravel: A present mechanic of the game, inspired by various books and films, including ''Film/BackToTheFuture''.

*** The achievement for traveling through time at least once is "[[Film/BackToTheFuture 88 Miles per Hour]]".

->''"To live a life of power, you must have faith that what you believe is right, even if others tell you you're wrong. The first thing you must do to live a life of power is to find courage. You must be ready to reach beyond the boundaries of Time itself. And to do that, all you need is the will to take that first step..."''

->'''YOU'RE TOO COOL!'''

* InstantWinCondition: Normally, to get the good ending in ''Sonic CD'', you have to go to the Past to find and destroy the Robot Generator in the first two Zones of every single Round. Missing even a single generator hardlocks you into the BadEnding. However, should you get all seven Time Stones before the end, you automatically get the good ending ''even if you missed every single generator beforehand''. Even better, any and all remaining levels you go through before the end will automatically show a Good Future whenever you go there. And if you're skilled, the earliest you can achieve this is the end of ''Quartz Quadrant Zone 1''; which is roughly halfway thru the game.

* FanRemake: Similarly to the Retro Engine remasters of ''Sonic 1'' and ''2'', ''Sonic CD'' also received a fan decompilation port that allows the Steam and mobile versions of the game to be played natively on PC and other platforms while providing unique benefits from both versions that one version didn't received from the other.[[labelnote:*]]The Steam version of ''Sonic CD'' didn't receive script updates that the mobile version has gotten, while mobile version has a different rendering backend that doesn't fully support palettes compared the Steam version.[[/labelnote]] The fan decompilation also has native support for user-created mods.

** A statue in Wacky Workbench Zone 1,[[note]]It's either an angel statue in the past that gives rings, or an Eggman statue that drops bombs in the Bad Future; finding the angel statue unlocks an achievement in the 2011 re-release, while in ''Sonic Origins Plus'', destroying the Eggman statue with either Amy or Knuckles will fill in part of the compilation's special illustration.[[/note]] some artwork, and a dummied out Special Stage are both hidden in the game.

-->-- '''Casey Rankin''' and '''Keiko Utoku''', "Sonic — You Can Do Anything".

->''"To live a life of power, you must have faith that what you believe is right, even if others tell you you're wrong. The first thing you must do to live a life of power is to find courage. You must be ready to reach beyond the boundaries of Time itself. And to do that, all you need is the will to take that first step..."''
-->-- Words taken from the Japanese cover of ''Sonic CD''.

->''Toot, toot, Sonic Warrior, deep in space and time!\\
Toot, toot, Sonic Warrior, forever in your mind!\\
Nothing can survive the will to stay alive\\
'Cause if you try, you can do anything!''

In May 2021, Sega announced that ''Sonic CD'' and the other mainline Genesis ''Sonic'' games would be [[CompilationRerelease compiled together]] in ''Sonic Origins'', which was released on June 23, 2022. This version, along with all of the other games in the compilation, runs on the Retro Engine. An update to ''Origins'', ''Sonic Origins Plus'', was announced in March 2023. It's slated to be released on June 23, 2023 as both a physical release and as an expansion pack for current ''Origins'' owners. This update adds Knuckles and Amy as playable characters. The original Sega CD version of the game is also one of 50 games included in the ''Mega Drive Mini 2'' microconsole, released in October 2022.

* PalmtreePanic: Thie TropeNamer is the first level of the game, and the local GreenHillZone.

** Quartz Quadrant happens in a cave with conveyor belts: while the past is a simple cave, the present is a CrystalLandscape, the Good Future is an UndergroundCity and the Bad Future is an abandoned factory.

* PalmtreePanic: This is the name of the first level of the game.

* UndergroundLevel: Tidal Tempest is underground and under water in the present.

*** Palmtree Panic is obviously inspired by the lush visuals of Green Hill Zone. The Tamabboh Badnik looks like a Moto Bug and behaves like a Crabmeat.
*** Collision Chaos has a [[JustForPun Spring Yard]] at the end of both Zones 1 and 2. The second zone also has two goals, just like Spring Yard Zone Act 2.

*** Stardust Speedway shares its level theme and position with Star Light. It plays rather differently, though, besides being fast-paced.

** A scrapped zone, Dubious Depths, likely would have stood in for Marble Zone -- it went in between Palmtree Panic and Collision Chaos, and apparently had a similar marble ruins theme.

* OffModel: Metal Sonic is depicted with a mouth in the Western box art, seemingly as a result of the artist misinterpreting a reflection in his muzzle in the Japanese cover as a mouth. His sprites also have gray eyes, compared to his artwork and all later appearances having red eyes.

** [[https://gamebanana.com/mods/50075 One mod]] for the Steam release adds newly-created Past tracks for the North American soundtrack, addressing the SoundtrackDissonance due to the original US composers being unable to replace the sequenced tracks.

* ReReleaseSoundtrack: The original Japanese soundtrack was kept for the European release, but the North American version replaced it with a whole new soundtrack mixed in [[https://en.wikipedia.org/wiki/QSound QSound]] (a positional audio algorithm that attempts to mimic surround sound through stereo speakers). However, only the Past tunes were kept, which led to a rather jarring problem: each stage had its main Present theme and three remixed versions (Past, Good Future, Bad Future), but the North American soundtrack only replaced the Present version and both of its Future remixes, leaving the remaining Past tune sounding nothing like its accompanying tracks. When the game was re-released in 2011, that version used the original Japanese soundtrack by default, but included the option to switch to the North American soundtrack.

''Sonic the Hedgehog CD'' (also known as ''Sonic CD'') is a ''Franchise/SonicTheHedgehog'' game released for the UsefulNotes/SegaCD in 1993 as a direct sequel to [[VideoGame/SonicTheHedgehog1 the original 1991 game]]. While it was released after ''VideoGame/SonicTheHedgehog2'', the games were developed in tandem, and as a result, have some notable differences between them; the CompilationRerelease ''Sonic Origins'' would later definitively confirm that ''CD'' takes place before ''Sonic 2'', helping explain at least a few of the discrepancies. This game introduced two {{Breakout Character}}s: Sonic's pink {{fangirl}} Amy Rose, and the EvilKnockoff Metal Sonic. The [[PreRenderedGraphics animated opening and ending sequences]] were done by Creator/StudioJunio and Creator/ToeiAnimation.

This time, Sonic explores Little Planet, a [[BabyPlanet tiny world]] orbiting Sonic's home planet. For one month out of the entire year, it appears over the Never Lake. Little Planet is the home of seven miraculous Time Stones that have been reported to cause wonders, such as preserving the natural world from the passage of time. To witness this phenomenon, Sonic journeys to Never Lake, but is shocked to find Little Planet encased in a metallic floating prison, chained to a mountain carved with the distinct face of [[BigBad Dr. Eggman]] ([[DubNameChange also known as Dr. Ivo Robotnik]]). The scientist seeks to use the Time Stones to rule over time itself.

Meanwhile, Amy -- who predicted that Sonic would be arriving at Never Lake by reading [[UsefulNotes/TarotCards Tarot cards]] -- tags along and gets kidnapped by Sonic's robotic doppelgänger, Metal Sonic. It's up to Sonic to save Amy, the future of Little Planet, and the entire timeline.

''Sonic CD'' was released in Japan with the original soundtrack on September 23, 1993, then in Europe on October 7, 1993.

North America later got the game with the redone soundtrack on November 19, 1993.

* ReReleaseSoundtrack: The original Japanese soundtrack was kept for the European release, but the North American version replaced it with a whole new soundtrack. However, only the Past tunes were kept, which led to a rather jarring problem: each stage had its main Present theme and three remixed versions (Past, Good Future, Bad Future), but the North American soundtrack only replaced the Present version and both of its Future remixes, leaving the remaining Past tune sounding nothing like its accompanying tracks. When the game was re-released in 2011, that version used the original Japanese soundtrack by default, but included the option to switch to the North American soundtrack.

* {{Expy}}:
** According to Naoto Ohshima, most levels, with the exceptions of Quartz Quadrant and Wacky Workbench, were made as more surreal versions of the original ''Sonic the Hedgehog'' levels. Even the level theme order is the same. Sometimes, the similarities are subtle, sometimes not:
*** In Palmtree Panic, the Tamabboh Badnik looks like a Moto Bug and behaves like a Crabmeat.
*** Collision Chaos has a [[JustForPun Spring Yard]] at the end of both Zones 1 and 2. The second zone also has two goals, just like Spring Yard Zone Act 2.
*** Tidal Tempest's graphics resemble Labyrinth's. The water current gimmick, which sends Sonic spinning underwater is used in the second zone.
*** Stardust Speedway shares its level theme and position with Star Light. It plays rather differently, though, besides being fast-paced.
*** Metallic Madness' spinning, disappearing and moving platforms and doors are all from Scrap Brain. There's also a GiantMook version of the Bomb badnik called Bigbom and each Zone has a unique background, just like Scrap Brain.
*** Kama-Kama/Robot Mantis, a Badnik in Collision Chaos based on Kama Killer/Slicer from ''Sonic 2'', but with linear instead of homing projectiles.
** The Time Stones clearly fill in for the Chaos Emeralds.
** Quartz Quadrant and Wacky Workbench strongly resemble Hidden Palace Zone and Cyber City Zone, respectively. These levels were designed in the early stages of ''Sonic 2''[='=]s development. However, they didn't make it into the final version (although elements from them did). It's quite possible that this was a conscious move, as ''Sonic 2''[='=]s developers had to cut several levels due to a tight deadline.

* SuspiciouslySimilarSubstitute: According to the developers, several of the areas in this game were designed as more surreal versions of the zones from ''VideoGame/SonicTheHedgehog1'', and even appear in the same order: PalmtreePanic is GreenHillZone, Collision Chaos is Spring Yard Zone, Tidal Tempest is Labyrinth Zone, Stardust Speedway is Starlight Zone, and Metallic Madness is Scrap Brain Zone. The similarities are less apparent because Quartz Quadrant and Wacky Workbench aren't based on anything, while there's no equivalent to Marble Zone (it was supposed to be Dubious Depths, the scrapped second round).