Proto:Sonic the Hedgehog (Genesis)

This page details one or more prototype versions of Sonic the Hedgehog (Genesis).

  This prototype is documented on Hidden Palace.

A prototype of Sonic the Hedgehog was released by Hidden Palace at Midnight (GMT) on January 1, 2021. It depicts the game midway through development. Many stages cannot be completed due to the lack of signposts and bosses; some (like Clock Work Zone Act 3 and Final Zone) haven't been started at all, or are obvious placeholder designs (like the Special Stage).

This build reveals a game that was originally tuned more for traditional platforming and exploration rather than for speed, which would eventually become the hallmark of the Sonic series. It also features a plethora of interesting content that was previously only seen in grainy magazine screenshots and raw gameplay footage, like the rolling checkered boulder in Green Hill Zone, the UFOs in Marble Zone, and Spring Yard Zone when it was still called "Sparkling Zone". Also, Splats the Bunny!

Long considered a holy grail by the Sonic community, a Sonic 1 prototype was sought after for nearly thirty years. This hunt and scarcity was in part due to the game being the first foray of the Blue Blur, and in part because publicity for the game was actually quite subdued, at least compared to Sega's later efforts.

During the time before this build surfaced, prototypes of all the other 16-bit Sonic games were discovered, dumped, and shared with the public. Along the way, there were also a few ROM hacks created as attempted guesses to what such a prototype would look and play like (such as the historic Sonic 1 Beta Hoax, one of the first ROM hacks ever created back in May 1999).

It wasn't until late 2020 that an individual by the name of Buckaroo found a cartridge containing this prototype, and released its contents through Hidden Palace (on New Year's Day) for gamers to enjoy. According to drx, this build was originally sent to an unspecified UK video game magazine in early 1991 for their pre-release coverage.

Download Sonic the Hedgehog (Genesis Prototype) File: Sonic_the_Hedgehog_(16-bit)_(Prototype).bin (512 KB) (info)

To do: Stuff to add that's not accessible in the base ROM without patches. Some of this might be in patches that are available on release: Changed chunks There's a lot of minor changes that one normally wouldn't notice (e.g. Sonic has no ceiling collision when hurt). There's also unused content from earlier builds that hasn't been removed yet. There's some unused HBlank code that when added back in will reveal a very early water test. Replace all of the choppy GIFs with videos. There's something missing, check the Sonic wiki and poke around in the ROM.

Sub-Pages

Unused Content Unused graphics, test objects, unfinished enemies, alternate debug displays... this build has it all.

Zone Differences

Normally, only eight stages are playable without the Level Select. In order: Green Hill Acts 1-3, Marble Acts 1-3, Sparkling Act 1, and Star Light Act 1. By this point, the level order was already changed, and the level select did not reflect this until REV01.

Final Zone isn't available in the Level Select, and levels use their early names. Every Zone contains many differences in the layouts themselves.

Zone ID 06, which is used in the final game for the ending, hasn't been implemented yet. Trying to access it by modifying the current Zone/Act address will lead to "ZONE ACT. 1" briefly appearing onscreen, followed by the game softlocking because no level data exists for this level slot.

However, the "Act 4" stage ID (03) is also functioning, to varying degrees. Most other levels either contain nothing or an object layout from the first Act of that stage. Notably, Green Hill's "Act 4" slot contains a complete (yet buggy) duplicate of Act 3, heavily implying it was once considered for the ending cutscene before being moved to its own level slot.

Green Hill Zone You can't stop the Rock.

Labyrinth Zone Thankfully, there's no water here.

Marble Zone The truth really was out there.

Star Light Zone Under heavy construction.

Sparkling Zone Good luck.

Clock Work Zone Before the big Scrap.

Special Stage

Map	Transition

There's only one Special Stage in this build, with a very simple and unexciting layout, implying that it was only a temporary design.

• Only C can be used to jump. A and B respectively speed up/slow down the stage's rotation counterclockwise and clockwise, and pausing the game will reset the rotation speed. There's no upper cap on the rotation speed, meaning it's possible to hold A or B for long enough to overflow it and have the stage start rotating in the other direction. It's stored as two bytes in address F782 in 68K RAM.
• Only two bumpers are in the entire stage.
• A few clusters of rings are present near the start point, but that's all until the player gets to the "Emerald".
• Instead of a Chaos Emerald to collect, an ordinary green block is used as a placeholder, which does nothing when touched.
• Goal tiles are split in two: the blue ones (with "GOAL" on them) don't animate or function, but their second frame (red tiles) will spin the stage around rapidly like normal before pausing for a moment, then resetting the stage.
• The player cannot enter object placement mode, despite debug mode being enabled by default in this build, and thus cannot move freely around or place objects of any kind.
• The UP and DOWN tiles - just one of each present in the whole stage - don't animate either, and seem to function like Reverse blocks instead of adjusting the rotation speed.
• Collision detection seems to be less refined, with Sonic being able to stick to tiles much easier than in the final game.
• No score summary is displayed upon exiting the stage.
• The screen fades to black when entering or exiting the Special Stage. The final game uses a special fade to white.

General Differences

ROM Header

The prototype doesn't yet have its own ROM header and instead contains basic template information, with no game name and a date stamp of 1989.JAN, implying that this build was somehow compiled before development had even begun. A reasonable estimation, based on visual cross-checking against UK prerelease coverage of Sonic, places this prototype around February/March 1991.

Pre-Game Content

Proto	Final

Instead of the well-known Sega logo and iconic "SEGA!" chant, this prototype uses the standard (and silent) palette-cycling Sega logo which opens most other Genesis/Mega Drive games. Unlike in the final game, the logo can be skipped at any point with Start.

The title screen immediately follows; there is no "Sonic Team Presents" card. (At the time, Sega did not normally credit their internal development teams within games.) Unfortunately, adding this screen also created a minor bug. More on that below.

Proto	Final

The prototype's title screen lacks the ™ symbol (not unlike the Japanese release), and features a flashing "Press Start Button" graphic that's absent from the final. It's still present in the game, but because the Sonic Team Presents screen clears half the amount of RAM it should, it never appears onscreen.

During attract mode, BGM doesn't immediately stop when the Sega logo is displayed; the music fades out slowly instead.

Early Demos

To do: Add restored demos, they were in earlier revisions of the article as Youtube embeds, but aren't here anymore. Fix inconsistent filenames

Green Hill Zone	Marble Zone	Sparkling Zone

Special Stage	Star Light Zone (Unused)

While the demo cycle only shows Acts 1 of Green Hill Zone, Marble Zone, and Sparkling Zone, a demo of Star Light Zone Act 1 is present. It's not normally seen due to the demo cycle having a total of 12 entries, but the demo player code forcing a loop after the sixth. The Special Stage demo also plays in between every stage, rather than being played only at the end of the demo order in the final release. There are no demos present for Labyrinth Zone nor Clock Work Zone.

At first glance, the demos would appear to be broken, as Sonic dies almost immediately by running into enemies or falling off the level. This is because the demo recordings are not only misreferenced, but belong to an earlier compile of the game.

Used	Unused
Green Hill 1	Star Light 1
Special Stage	Special Stage
Marble 1	Marble 1
Special Stage	Special Stage
Sparkling 1	Sparkling 1
Special Stage	Special Stage

Level Select/Debug Mode

Level Select and Debug Mode are enabled automatically in this build for testing and preview purposes.

• In debug, holding A and pressing C won't yet go backward in the object list, and instead places the highlighted object regardless.
• The game acknowledges B as a jump input before activating debug mode with the same button. This causes Sonic to jump on the frame before entering debug mode and performing said jump after exiting debug mode. This was fixed for the final version for levels, but was not changed for the Special Stages.
• Spring Yard and Scrap Brain were called Sparkling and Clock Work in this build. These early zone names would end up being used in the Sonic the Hedgehog manga published in the Japanese magazine Mega Drive Fan, which coincided with the release of the game.
• The level select contains Xs next to Star Light Acts 1-3 and Clock Work Act 3. These were likely used for when a stage hasn't been implemented yet (though in this build it's a bit outdated, since Star Light has been implemented).
  • Clock Work Act 3 cannot be selected.
• Pressing B on the Level Select will load up Act "4" of Green Hill (displayed on the title card by a copy of the blue oval graphic replacing the Act number), which suggests that it might have been used to test the ending sequence stage. In the final game, the ending stage instead uses a separate Zone altogether (06).

Proto	Final

Level Transitions

• Completing Act 1 or 2 of Star Light will send the player to Act 2 or 3 respectively, but clearing Act 3 takes the player to Marble Act 1.
• Beating Clock Work Act 2 will bring the player to Act 3 (which later became Final Zone), and beating Act 3 will bring the player to the Sega screen.

Gameplay

HUD Differences

Proto	Final

• As seen in countless prerelease screenshots, the HUD says "Ring" instead of "Rings". The change was made circa the build seen in Shinsaku Soft Video, rather close to the end of development.
  • "Ring" does not flash red when the player has 0 rings, nor does "Time" flash when the clock reaches 9:00.
  • A "Time Over" does not occur when the timer reaches ten minutes. The timer instead loops back to 9:00 indefinitely.
  • The time bonus works differently.
  • During a Game Over, the timer will continue counting up. The final game stops the timer.

Sonic

• Sonic's jump height is lower. On flat ground, the apex of his jump is 6 pixels lower than in the final.
  • The cause is in one of the global subroutines that handles object movement: in this prototype, gravity takes effect instantly. In the final game, the code was modified to take 1 frame for gravity updates to apply.
• Sonic's collision height doesn't change when crouching.
• Sonic's deceleration speed is slower, being $40 in the prototype and $80 in the final. The Power Sneakers' deceleration speed is $80 in both this build and the final game, indicating that it was never adjusted to account for the regular deceleration speed's change, resulting in the Power Sneakers deceleration speed and regular deceleration speed being identical in the final.
• Walking/jumping onto objects such as platforms and bridges causes Sonic to lose some of his speed.
• When hurt, Sonic has no collision with ceilings.
• Sonic doesn't automatically run off the screen after touching the end-of-level signpost and destroying the post-boss Animal Capsule, nor is the player capable of doing so yet. Jumping during the ensuing end-of-level bonus tally causes Sonic to enter the "victory fist pump" pose seen in many prerelease screenshots.

Objects

To do: Perhaps a comparison video between the proto and final Special Stage ring animations should be added.

• The hidden end-of-Act bonus point markers haven't been implemented yet.
• Special Stage rings haven't been added to the end of Acts 1 and 2 yet. The ring object does exist with full graphics and coding, though it works completely differently from the final game:
  • When Sonic touches the giant ring, instead of instantly disappearing like in the retail version, he instead momentarily gains a "sparkle" effect, after which he then "warps" off of the screen (similarly to the way time travel works in Sonic CD). However, there doesn't seem to be any further coding for it beyond this point in development, as Sonic simply reappears a short distance ahead of the point where he vanished a brief moment after he disappears.
  • Given this behavior, it's probable that the Special Stage rings were originally intended to be placed at ground level just past the signpost instead of up in the air, to give the illusion of Sonic running through the ring and then warping away to the Special Stage. Why this was altered is unknown, but given that remnants of this functionality still exist in the final ROM, it's likely that it was changed fairly late in development.
• Checkpoints are completely absent. In fact, they haven't been coded into the game at all at this point.
• Spikes damage Sonic during all forms of invincibility, including from monitors.

Screens

• The Continue screen hasn't been implemented yet, likely because there's no normal way to earn Continues in this build.
• The ending cutscenes and credits are completely absent.

Scrolling System

Vertical positioning is somewhat buggy:

• The camera is much slower when moving vertically, making it easier to outrun the camera (and, in some rare cases, die when doing so) when falling or traveling at high speeds.
• The top and bottom of the stage wrap in every level, even in stages that don't normally utilize vertical wrapping. In stages with lethal pits, this results in the player dying if they travel above the upper stage limit (since Sonic wraps from the top to the bottom of the stage, where the game then thinks he's fallen into a pit).

Debug Mode

Proto	Final

• Object placement mode ignores camera boundaries. Camera movement also works differently, meaning going to the same coordinates in the same way won't always result in the camera being positioned the same way.

Miscellaneous

Proto (GHZ)	Final (GHZ)

Proto (MZ)	Final (MZ)

• When a Zone is completed, graphics for the next Zone start decompressing during the fade-out, before the Act transition completes.
• Collision is noticeably glitchy, especially when rounding a small incline.
• There is no combo bonus for destroying multiple Badniks in a row yet, meaning you will always get a flat rate of 100 points from doing so.
• Onscreen enemies are not cleared after finishing an Act, and can still harm Sonic while the player's score is being tallied. (This can be easily observed in GHZ Act 1.)
• Extra lives are earned at 50 and 100 rings. The ring requirement for extra lives was later doubled to 100 and 200 in the final release.
  • "Ring memory" doesn't exist yet, meaning it's possible to earn two 1-Ups by collecting 100 rings, take damage, and then earn another two 1-Ups by collecting 100 more rings. In the final release, each ring threshold only grants one 1-Up per life, per level.
• BGM and sounds continue while the game is paused.

Graphical Differences

Proto	Final

• Title cards have an additional period after "ACT", possibly implying that "ACT" was originally an abbreviation of another, longer word, like "action". This was removed from the final, although the period remains in the data.
• Sonic's sprites are almost identical to the final game, but he lacks his updated "breathing" animation and his extra hurt sprite (used for slides).

Audio

Original TR-626 Sample	Proto	Final

The snare drum and timpani samples used across all tracks are pitched lower than the final release, as the final game had its DAC driver code rewritten to accommodate the "SEGA!" chant, which resulted in all samples being played at a higher pitch. Curiously, the kick drum had its pitch manually lowered in each track in the final game to compensate for the driver change.

Additionally, the extra life theme seems to cause various minor issues with the sound driver for a brief moment after it finishes playing.

Music

ID	Title	Proto	Final	Notes
$85	Sparkling Zone			The track has a single note difference in the bassline. The final version simply reuses a section that's present earlier in the track, probably to further optimize the song. The original bassline note still exists in the final game's credits medley. A note was also played for a shorter amount of time in the final version.
$8B	Ending			Slightly slower than the final track, and the high pitched lead synth lacks a decay. Goes unused in this build.
$8D	Final Zone			Goes unused in this build.
$90	Continue Screen			Goes unused in this build.
$91	Credits Medley			Much of the instrumentation is either slightly different or missing.
$92	Drowning			Crashes the game as it uses invalid pointers.
$93	Got Chaos Emerald			Completely missing; selecting this sound ID does nothing.

Sound Effects

There are many unused sounds unique to this prototype, which would go on to be replaced by different sound effects in the final.

ID	Sound	Notes
$A1		Similar to the sound played when touching Goal blocks in the Special Stage. Replaced by the checkpoint sound in the final release.
$A8		A noise sound effect that then decreases in pitch. Replaced by the aforementioned Goal block sound effect. This sound is used with the unused warping object.
$A9		A longer, higher-pitched version of the rolling sound. Replaced by the sound used for touching speed/Reverse blocks in the Special Stage.
$AD		A duplicate of the "badnik destroyed" sound effect, which lacks noise PSG. Replaced by the air bubble sound, but later used in Sonic CD, Sonic 3, and Knuckles' Chaotix.
$B0		A low-pitched siren sound. Replaced by the buzzsaw sound effect.
$B1		A faster, higher-pitched siren which sounds like it was taken straight out of Pac-Man. Replaced by the sound effect used for Scrap Brain's electricity balls.
$B2		Sounds like a buzzer of some sort. Replaced by the drowning sound effect. From 0x7D3EE - 0x7D415. This same sound (albeit with a one-byte difference) can be found in Michael Jackson's Moonwalker starting at 0x68502.
$B3		A rough, low-pitched sound that quickly rises and falls in pitch. Replaced by the sound used by the falling fireballs in the Marble Zone boss fight.
$BA		Resembles the sound used by the color-changing bars in Casino Night Zone from Sonic 2. May have been an early version of the sound used by the color-changing blocks in the Special Stage, which ultimately ended up replacing this sound.
$BF		Two quick, harsh-sounding noises that loop indefinitely. Replaced by the Continue sound effect.
$C2		An alternate version of the "Badnik destroyed" sound effect, with one of the sound channels being a bit harsher. Replaced by the underwater timer "ding" sound effect.
$C3		A deeper version of the bomb explosion sound (which, incidentally, occupies the next sound slot). Replaced by the sound effect used when entering a giant ring.
$C9		A harsh, vibrating noise. Replaced by the noise used when touching end-of-stage point markers.
$CA		Sounds like footsteps walking away; could have possibly been used as an "exit" sound effect for something at some point. Replaced by the Special Stage warp noise.
$D1		A louder version of the waterfall found in Green Hill Zone. This and the next one were completely deleted in the final game. From 0x7DA92 - 0x7DABD. This same sound can be found in Michael Jackson's Moonwalker, starting at 0x6869C.
$D2		A strange rhythmic pounding sound. This, and the previous sound, won't end when they are played in-game. From 0x7DABE - 0x7DB09. This same sound can also be found in Michael Jackson's Moonwalker, starting at 0x686C8.