Proto:Sonic the Hedgehog (Genesis)

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

This prototype is documented on Hidden Palace.

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:

night palette
unused/leftover layout data for ghz
leftover old debug styles - see the prerelease page for details
There's a lot of changes, including minor things 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; one bit, Obj02-07, appears to be leftovers from the February 1990 prototype.
etc.

The Sonic the Hedgehog prototype is an early build of Sonic's debut game, and extremely incomplete. 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).

Playing this prototype reveals a game that was originally tuned more for traditional platforming and exploration, rather than for speed, which became the hallmark of the Sonic series. It also features a plethora of cut content that was previously only seen in grainy magazine screenshots and blurry video footage, like the giant rolling ball in Green Hill Zone, the UFOs in Marble Zone, and Spring Yard Zone when it was still Sparkling Zone. Also––Splats the Bunny!

This cartridge was sought after for over twenty years, during which time prototypes of all the other 16-bit Sonic games were eventually found, until it was finally dumped in late 2020 by Buckaroo, and released on January 1, 2021 (12:00am GMT) by drx.

The prototype was confirmed to be sourced from a UK magazine, but not any particular one as of now.

Download Sonic the Hedgehog (Genesis) (Prototype)

File: Sonic_the_Hedgehog_(16-bit)_(Prototype).bin (512 KB) (info)

Zone Differences

If played normally, only 8 stages are present: Green Hill Zone (all three Acts), Marble Zone (all three Acts, but no boss), Sparkling Zone (Act 1), and Star Light Zone (Act 1). The game then returns to the title screen.

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

Clock Work Zone Act 3 can't be selected, but can be warped to by modifying 68K RAM address (FE10) during level load. This can be done using the following Action Replay code:

FFFE10:0502

It seems to act as a normal Act 3, instead of being effectively "Labyrinth Zone Act 4". Notably, trying to load "Labyrinth Zone Act 4", the level slot that the final Scrap Brain Act 3 occupies (stage 01-03), instead loads a copy of Labyrinth Zone Act 3, indicating that the concept hadn't even been conceived yet at this stage in development.
The stage is completely empty; Sonic just falls forever, due to lethal pits not having been implemented in this stage.

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

However, the "Act 4" Stage ID (03) for every other zone besides Labyrinth 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 Zone's "Act 4" slot contains a complete duplicate of its third act, heavily implying it was once considered for the ending cutscene instead before being moved to its own zone altogether.

Green Hill Zone
You can't stop the rock.

Marble Zone
UFOs are real.

Sparkling Zone
Good luck.

Labyrinth Zone
Thankfully, there's no water here.

Star Light Zone
Under heavy construction.

Clock Work Zone
Before the big Scrap.

General Differences

Opening, Demos & Level Select

The ROM header hasn't been filled out yet, with a generic date just reading "1989.JAN"; because of the fact that development began in very early-1990, this means an exact date for this prototype cannot be pinpointed.

Prototype	Final

The SEGA screen uses the generic palette-cycling logo seen in most other Genesis games, instead of the unique screen with the now-famous "SEGA" chant. It can also be skipped with the Start button. Following that, the "SONIC TEAM PRESENTS" screen is absent.

Prototype	Final

The title screen is missing the trademark and has the text "PRESS START BUTTON" below. This remains in the final game but was accidentally dummied out when the "SONIC TEAM PRESENTS" screen was implemented, due to its memory not being cleared correctly. Stage music doesn't stop when the SEGA screen is displayed either, instead fading out as normal.

Green Hill Zone	Marble Zone	Sparkling Zone	Special Stage

The demos haven't been re-recorded from an earlier build; Sonic dies almost immediately by running into enemies, with no player interaction needed. The Special Stage demo also plays in between every stage, compared to being played only at the end of the demo order in the final release.

Prototype	Final

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 place the highlighted object regardless.
Also in debug, when pressing the A button, the game still acknowledges the jump input prior to entering object placement mode, causing Sonic to rise into the air slightly when exiting object placement.
Spring Yard and Scrap Brain are called Sparkling and Clock Work in this build, though the latter displays as "Clock Ork" since the title card font doesn't contain a W.
The level select contains Xs next to Star Light Zone and Clock Work Zone Act 3; these were likely used for when a stage wasn't implemented (though in this build it's a bit outdated, since Star Light Zone has been implemented).
Clock Work Act 3 cannot be selected; attempting to load the level using a level modifier code reveals that the stage is completely empty.
Pressing B on the level select will load up Act "4" of Green Hill Zone (displayed on the title card by a copy of the blue oval graphic replacing the Act number), which suggests that it might've been used to test the ending sequence stage. In the final game, the ending stage instead uses a separate zone altogether (06).

Special Stage

There is but a single Special Stage in this prototype, with a very simple and unexciting layout implying that it's only a temporary design.
Only the C button may be used to jump.
A and B speed up/slow down the stage's rotation, respectively, and pausing the game will also reset the rotation speed.
Only two bumpers are in the entire stage.
A few clusters of rings are placed 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 prototype, 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 doesn't fade to white when entering or exiting the Special Stage.

Gameplay

Prototype	Final

There are several differences with the HUD:
- As was documented in countless prerelease screenshots, the HUD says RING instead of RINGS. The change was made circa the Shinsaku Soft Video build, 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.
- 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 unlike the final which stops the timer.
Sonic cannot run off the screen after touching the end-of-level signpost or destroying the post-boss prison capsule. Jumping during the ensuing end-of-level bonus tally causes Sonic to enter the infamous "victory fist pump" pose seen in many prerelease screenshots.
The hidden end-of-level bonus point markers haven't been implemented yet.

To do:
Perhaps a comparison video between the proto and final special stage ring animation should be added.

Special Stage rings haven't been added to the end of Acts 1 and 2 yet. However, 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 beyond that at this stage 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 currently unknown; however, given that remnants of this functionality still exist in the final game, it's likely that it was changed fairly late in the game's development cycle.
Checkpoints are completely absent; in fact, they haven't been coded into the game at all at this point in development.
Extra lives are earned at 50 and 100 rings, instead of 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.
The Continue screen hasn't been implemented yet, likely because there's no normal way to earn Continues in this build.
The end cutscenes and credits are completely absent.

Spikes damage Sonic during all forms of invincibility, including from monitors.

Vertical positioning is extremely 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 single 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 to the bottom of the stage, where the game then thinks he's fallen into a pit).

Prototype	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.

Prototype	Final

Prototype	Final

When a zone is completed, graphics for the next zone start decompressing during the fade-out, before the act transition completes.
If the player touches the sky with the help of debug mode, sometimes Sonic will die, or sometimes the camera will go all wonky for a second.
Collision is noticeably glitchy, especially when rounding a small incline.

Graphical Differences

To do:
There's more.

Prototype	Final

Title cards have an additional period after "ACT". For whatever reason, this was removed from the final.
Sonic's sprites are almost identical to the final game, but he lacks his updated 'breathing' animation and his extra hurt animation (used for slides).

Unused Sprites

To do:

Upload any recent discoveries here.
Show the restored UFO animation in action alongside its in-game version.
Also, there are more unused sprites.

Sprite	Location	Notes
	`$018000`	An 8x8 font with 3 copies in different colors. The palette used in this image is a mock-up.
	`$02656E`	A smoke sprite is loaded where the checkpoint will be in the final version. It is not yet possible to know what this is.
	`$02A386`	Ball Hog is completely programmed in the prototype, but its movement, sprites, and attack are different from the final version. It walks from side to side and drops bombs down vertically. This seems to match the version seen in early prerelease footage rather than the version seen in leaked Digitiser artwork from the game's development.
	`$060864`	A spring included in the boss attachments art file. Parts of this sprite are used on the boss of the Marble Zone.
	`$06512E`	A skull meant for the Special Stage; use unknown, though it probably had something to do with either death or losing.
	`$0651FE`	A U shaped item meant for the Special Stage. It resembles a magnet when given Sonic's palette. Use unknown.
	`$06C8A0`	A 6th frame for the animated UFOs in Marble Zone. To properly restore it in the animation script, use the PAR code `011430:0006`

Unused Objects

To do:

Upload images of other unused objects, so they can see the graphics and movement of them.
Describe the objects what they do in the build

The list of objects by offset can be found at the ROM address at $8580

Altogether there are 94 objects in the version of this prototype; compare to the final version's 140.

Object ID	Object Name	Note
09	Special Stage Sonic
14	MZ/SLZ fireball
1B	LZ water surface
1D	Unused switch
1E	Ball Hog	Ball Hog's behavior is different from the final version.
20	Ball Hog bomb
29	Points graphics
2A	SBZ one-way barrier
2C	Jaws	Used in the final, but not in the proto. Supposed to be used in Labyrinth Zone.
2D	Burrobot	Used in the final, but not in the proto. Burrobot in the version of this prototype uses the second palette line instead of Sonic's.. It also does not start buried in the ground.
35	Stationary fireball (MZ)
4A	Special Stage entry	A special effect discarded from the final version, this allowed Sonic to enter a Special Stage after touching a giant ring.
4B	Giant ring	Does not take you to Special Stages.
4F	Splats	A scrapped enemy accessible via debug mode in Marble Zone.
5E	Seesaws (SLZ)	Only accessible through debug mode.

Unused Object Positions

Sparkling Zone 1

Located at 0x729CA in the prototype is an unreferenced object position list that is presumably used for Sparkling Zone 1. Loading it in-game shows a number of differences, including Crabmeats near the entrance which are spawned on top of each other. To load, open the prototype in your favorite hex editor and go to 0x70040 and replace 2460 with 29CA. You'll then be able to see the changes in SZ1. Interestingly, the object positions seem to match up with an early Sparkling Zone layout seen in screenshots of the CES and CES-like builds.

Sounds

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

Sound $A1

Similar to the sound played when touching Goal blocks in the Special Stage. Replaced by the checkpoint sound in the final release.

Sound $A8

Resembles a rocket or something similar taking off. Replaced by the aforementioned Goal block sound effect. This sound is used with the unused warping object.

Sound $A9

A longer, higher-pitched version of the rolling sound. Replaced by the sound used for touching speed/Reverse blocks in the Special Stage.

Sound $AD

A duplicate of the "badnik destroyed" sound effect. Replaced by the air bubble sound.

Sound $B0

A low-pitched siren sound. Replaced by the buzzsaw sound effect.

Sound $B1

A faster, higher-pitched siren which sounds like it was ripped straight out of Pac-Man. Replaced by the sound effect used for Scrap Brain's electricity balls.

Sound $B2

Sounds like a buzzer of some sort. Replaced by the drowning sound effect.

Sound $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.

Sound $BA

Resembles the sound used by the color-changing bars in Sonic 2's Casino Night Zone. 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.

Sound $BF

Two quick, harsh-sounding noises that loop indefinitely. Replaced by the Continue sound effect.

Sound $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.

Sound $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.

Sound $C9

A harsh, vibrating noise. Replaced by the noise used when touching end-of-stage point markers.

Sound $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.

To do:
Export sounds $D1-$D3.

Sound $D1

A louder version of the waterfall found in Green Hill Zone. This and the next three were completely deleted in the final game. 300px

Sound $D2

A strange rhythmic pounding sound. 300px

Sound $D3

A fiery noise that progressively oscillates. This and the previous two sounds don't end when playing in-game. 300px

Music

General Differences:

The snare drum samples used across all tracks are pitched lower and of a much higher quality than the final release, due to the sound driver not being updated to accommodate the "SEGA" chant.
Stage music keeps playing even when the game is paused.
The extra life theme seems to cause various minor issues with the sound driver for a brief moment after it finishes playing.

$8B (Ending Theme)

Prototype	Final

Slightly slower than the final track, and a couple of instruments towards the end are held for a bit too long. Goes unused in this build.

$8D (Final Zone)

Prototype	Final

Goes unused in this build.

$90 (Continue Screen)

Prototype	Final