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Proto:Sonic the Hedgehog 2 (Genesis)/August 21st, 1992

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This page contains changes which are not marked for translation.
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This is a sub-page of Proto:Sonic the Hedgehog 2 (Genesis).

Hiddenpalace.org logo.png  This prototype is documented on Hidden Palace.

So very stubbly.
This page is rather stubbly and could use some expansion.
Are you a bad enough dude to rescue this article?
Please elaborate.
Having more detail is always a good thing.
Careful, you'll lose an eye.
This page or section needs more images.
There's a whole lotta words here, but not enough pictures. Please fix this.

The August 21, 1992 prototype of Sonic the Hedgehog 2 is quite similar to the Simon Wai build, but is getting closer to the final game. Most of the content is still as it was in the Wai proto (including the presence of Hidden Palace Zone and Wood Zone), but Sonic's sprites have been finalized, some of the bosses have been implemented, and most of the music is finished. Also, pink Casino Night!

This build was released by drx on November 10, 2019 as part of Hidden Palace's Sonic Month.

To do:
This disassembly should help.
  • Bubbler's Mother, Bubbler, and the metal ball have their code implemented but are unused.
Download.png Download Sonic the Hedgehog 2 (Aug 21, 1992 proto)
File: Sonic_the_Hedgehog_2_(Aug_21,_1992_prototype).bin (2 MB) (info)

General Differences/Notes

  • The level order has been changed from the Simon Wai build.
    • Simon Wai: Aquatic Ruin, Chemical Plant, Hill Top, Emerald Hill.
    • August 21: Emerald Hill, Chemical Plant, Hill Top, Mystic Cave, Metropolis, Aquatic Ruin.
  • The explosion sprites now match their final Sonic 2 counterpart. The light-green color in Hidden Palace affects them.
  • The bubble sprites in Hidden Palace have been fixed.
  • Collecting 100 rings still plays music track $88, which was the extra-life sound in Sonic 1 but is now the Casino Night 2-player theme.
  • Bosses for Chemical Plant, Aquatic Ruin, Oil Ocean, and Metropolis have been implemented, but don't load in their respective levels.
  • Tails acts identically to previous builds.
  • Drowning plays music $8A, which is the Death Egg theme in this build.
  • The boss music, which was $8E in the Simon Wai build, is now Chemical Plant here.

Sound Differences

Most of the game's music tracks have been implemented and all have been finalized, sans the credits theme, which was added in the September 14th build.

  • While all sound effects are implemented, not all of them are used yet.
  • The spindash sound's pitch-shift messes with some sounds.
  • The invincibility music has a different ending:
August 21 Final
  • The final Hidden Palace song appears twice in the Sound Test as tracks 90 and 9E. The latter slot is occupied by the credits theme in the final version.

Super Sonic

Super Sonic is present in this build and can be easily accessed by destroying the [?] Monitor, which can be added through Debug Mode.

  • Super Sonic already has a cycling palette, but it was not implemented for when Sonic was underwater. This makes Super Sonic retain the normal Sonic color palette underwater; this was partially fixed until the final, although transforming underwater still uses the non-Super Sonic palette.
  • Rings are not consumed while the Super form is active.
  • Super Tails simply gets invincibility.
  • The invincibility is timed, taking the same time as the invincibility powerup.
  • Once the invincibility runs out, Super Sonic is able to use powerup monitors.


Oil Ocean Zone
Why is there floating oil?
Casino Night Zone
Solid floors now!

Emerald Hill

Sonic2 Emeraldhill Aug21.png
  • The snail badnik from earlier builds has been replaced with Coconuts, though its coding is still present. Interestingly, its ID was changed from $54 to $59.
  • The boss acts near identically to the Simon Wai build, but is now capable of exploding again.
  • The boss plays the Chemical Plant theme. This is because it's still playing music $8E, which was the boss track in the Simon Wai prototype, but has since moved to $93 with Chemical Plant's theme taking its place.

Hill Top

Sonic2 Hilltop Aug21.png
  • The boss arena is different, and wider than the one in the final version.
  • A small chunk of wall can be found above the boss arena at the top of the level.

Mystic Cave

Sonic2 Mysticcave Aug21.png
  • Object placement is now much closer to the final version.
  • The boss acts differently.
  • Crawlton badniks use the second palette line in this build making them look slightly off.
  • Flasher badniks use a simple yellow ball as their flashing animation, while the final game adds shading.
  • Act 2 still has the triple swinging platform.
  • The upper route in Act 2 is much harder than the final game.
  • The very top route from the Simon Wai prototype has been blocked off but can still be accessed via Debug Mode and actually has a few rings placed.
  • Drill Eggman II has more erratic movements than the final.
(Source: Sonic Retro)


Sonic2 Metropolis Aug21.png
  • Somehow, the animation for entering a tube has become corrupted in this build.
  • The background and cogs still have their old design from the Simon Wai prototype.
  • Oddly, Act 3's boss seems to better fit Act 2's layout according to the source code.
  • There's an area in Act 1 that can allow the player to fall forever, and eventually the player can accelerate so fast the the game will propel the player up.
  • Lava in this stage does not function yet.
  • Nuts will continue to go up even when reaching above the screws.
  • While the boss is implemented, Act 3 instead has a signpost at the end.
(Source: Sonic Retro)

Hidden Palace

Sonic2 Hiddenpalace Aug21.png

Hidden Palace's layout remains the same as it was in the previous two builds, and still uses the Mystic Cave 2-player music even though the track used in the final is present. However, it did have some behind-the-scenes changes, which seem to suggest there were plans to continue working on it before being scrapped:

  • Stego was added to the debug object list.
  • Vertical wrapping has been implemented for objects (such as badniks), as opposed to the Nick Arcade and Simon Wai prototypes where badniks that fell off the bottom of the stage simply disappeared (see the video to the right).

Wood Zone

Sonic2 Wood Aug21.png

Exactly the same as it was in the Simon Wai build. It's still incomplete and ends pretty quickly, with Metropolis' music playing in the background.

Genocide City

Sonic2 Geonocidecity Aug21.png

Exactly the same as it was in the Simon Wai build... which means it's just an empty level slot with Chemical Plant's music playing.

Death Egg Zone

Sonic2 Deathegg Aug21.png

Exactly the same as it was in the Simon Wai build. Dying here still causes all sound to cut off, unless you activate Super Sonic in which case his theme will play continually until you reset the system.

Special Stage

Unlike previous builds, the Special Stage can be accessed in this build - but there's a catch: It will only load on less-accurate emulators such as Kega Fusion(and some other low-accuracy emulators, including most Android ones). Even if you do access the Special Stage, there's a very high chance of it locking up. Accessing it on real hardware causes the game to fade to white and softlock; the level select music continues.

All this aside, the Special Stage here appears to be a very corrupted version of the Sonic 1 Special Stage with the Casino Night music playing. While you can make out what's going on, the graphics are corrupted, making everything pretty hard to see. Hitting a GOAL block or getting the Chaos Emerald triggers a blue screen playing Chemical Plant's music and touching any blocks that change the rotation of the stage will result in a crash.

Ocean Wind Zone

Sonic2 Oceanwind Aug21.png

Exactly the same as the Simon Wai Prototype, being an empty level slot playing with Emerald Hill's palette and music. Entering the level without debug mode just results to Sonic falling to his death.

Sand Shower Zone

Sonic2 Sandshower Aug21.png

Exactly the same as the Simon Wai prototype, being an empty level slot with Emerald Hill's palette and Oil Ocean's music. Entering the level without debug mode results to Sonic falling to his death.

Blue Lake Zone

Sonic2 Bluelake Aug21.png

Exactly the same as the Simon Wai prototype, being an empty level slot with a pitch black background and what would become Emerald Hill's 2 Player mode music. Entering the stage without debug mode results to Sonic falling to his death.

Rock World Zone

Sonic2 Rockworld Aug21.png

Exactly the same as the Simon Wai prototype, being an empty level slot, using Emerald Hill's palette and Sky Chase's music. Entering the level without debug mode results to Sonic falling to his death.

Graphical Differences

  • Sonic and Tails' sprites are now their final versions.
  • Stego/Stegway has its updated sprite, but uses the incorrect palette.

Unused Content

To do:
Add graphics for the rest of the objects

Metropolis Block

Sonic2Alpha MTZ Moving Block.png

The moving blocks from the Simon Wai prototype can still be placed, though it doesn't move anymore.


You think they overdid the placement a bit?

The infamous Slicer badnik can be also placed in Debug Mode, though it's slightly buggy; it uses the wrong palette line and only attacks when the player is behind it.

Chemical Plant/Death Egg Door

Sonic2 CorrectDoor.png

The door for Chemical Plant and (eventually) Death Egg Zone, which also go unused in the final as both levels use the Hill Top Zone version.

Aquatic Ruin Door

Sonic2gen Aquatic ruin door.png

The unused door for Aquatic Ruin Zone in the final also exists.

Chemical Plant Boss

The Chemical Plant Zone boss isn't loaded in said stage yet, but is fully functional when hacked in.

Aquatic Ruin Boss

The boss is near complete, though the totems can not be interacted with yet, and the boss also moves much slower than the final.

Metropolis Boss

A preliminary version of the Metropolis Zone boss exists.

  • Eggman doesn't move, but will still release his balloons.
  • Balloons act like regular badniks.
  • The orbs around Eggman can be destroyed.
  • There is no win condition for the fight. That means if the boss is beaten, the game will crash.
(Source: Sonic Retro (CNZ block, auto-rolling graphic and bosses))