Proto:Sonic the Hedgehog (Genesis)

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

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This prototype is documented on Hidden Palace.

Download Sonic the Hedgehog (Genesis) (Prototype)

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

To do:
A lot.

The Sonic the Hedgehog prototype is an early build of the game and extremely incomplete; many stages cannot be completed due to the lack of signposts and bosses, and some (like Clock Work Act 3) haven't been started at all. It does, however, give some insight into the game's development.

This prototype was sought for 15 years, and was finally recovered and released on January 1, 2021 by drx and Buckaroo.

Zone Differences

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 crashing because no level data exists for this level slot.

Green Hill Zone
Remember those magenta flowers?

Marble Zone
Those UFOs were real after all.

Sparkling Zone
"Good Luck"? "Goodbye"?

Labyrinth Zone
This puts the "Labyrinth" in Labyrinth Zone.

Star Light Zone
Something doesn't feel right.

Clock Work Zone
Oh sorry, I meant Clock Ork Zone.

General Differences

Opening, Demos & Level Select

The ROM header hasn't been filled-out with information yet, with the date just reading "1989.JAN".
- This means an exact date for this Prototype cannot be obtained.

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.
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, instead fading out as normal.

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

To do:
This map is a placeholder: upload a better map.

Special Stages are in a very early state with only one stage present, which is clearly just a test layout.
- Special Stages do not use a unique animation when entered, the A and B buttons also cannot be used to jump, and object placement mode cannot be entered. A and B speed up/slow down the stage's rotation and pressing START will reset the rotation speed.
- Chaos Emeralds are nowhere to be found (though their graphics do exist in the ROM), and 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 UP and DOWN tiles 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.

Gameplay

Prototype	Final

There are several differences with the HUD:
- As infamously documented in several prerelease screenshots, the HUD reads "RING"; an "S" was added shortly before the final release.
- "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.
Sonic doesn't 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.
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).

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

Graphical Differences

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.

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.

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