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Proto:Sonic the Hedgehog CD (Sega CD)/v0.51

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This is a sub-page of Proto:Sonic the Hedgehog CD (Sega CD).

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v0.51 is a mid-development build of Sonic CD, dated June 21, 1993. It was dumped by drx on October 26, 2019 as part of Sonic Month, alongside five other Sonic CD prototypes.

The game has been significantly updated since v0.28a, with all the groundwork laid out and most levels being feature-complete, though there's still a lot of differences.

General Differences

  • The music does not stop when the game is paused.
  • The time travel indicator on the HUD is still missing.
  • A large amount, if not all, of the PCM sounds are implemented.
  • When time traveling, the sound used is a CD audio track instead of an FM sound like in earlier prototypes or a PCM sound in the final. Interestingly, this track became unused later in development, still exists in the final build's CD audio tracks, and is labeled as "Metal Sonic" on the OST.
  • The badnik teleporter makes no sounds when destroyed.
  • Giant Rings make sounds when entering, but they do not animate when you jump into them.
  • The Special Stage demo is actually controllable, much like in the 712 prototype.
  • When debug mode is enabled, certain sprites that control Sonic (like in tubes) can be seen if the player gets a shield, invincibility, etc.
  • There are various Blue Ring monitors and Clock monitors placed throughout the levels. The Clock monitors work as they did in earlier prototypes, but the Blue Ring monitors have a new functionality - they grant an invisible shield that can be stacked with the normal shield as well.

Graphical Differences

  • Sonic's face on the signpost is the same one from the 510/v0.28a prototypes.

Audio Differences

  • The noise for defeating enemies is the one from v0.28a and earlier.
  • When getting a 1-Up, a different PCM voice sample is played. This voice would later wind up unused in the final build.
v0.51 Final
v0.51 Final
  • All of the Past PCM tracks excluding Quartz Quadrant's are implemented in this build. However, there are a few with some noticeable differences: Palmtree Panic's Past PCM track is unsynchronized, while Collision Chaos' track plays a bit faster, has slightly different instrumentation, and volume levels are different for the instruments.
  • The unused PCM tracks in the 712 prototype exist in the game data, though the "D" variants are simply copies of the "B" variants.

Title Screen

v0.51 Prototype 712
Sonic-CD-v0.51-Garbled-Title-Screen.png SonicCDJPtitle.png

The graphics have been nearly finalized, though the copyright text is thinner compared to later prototypes.

Stage Differences

Palmtree Panic

  • There is some unusual layout placement next to the giant ramp in the beginning of Act 1.
  • Act 3's graphics have been updated at this point.
  • The boss in Act 3 has finalized graphics.

Collision Chaos

  • Metal Sonic now has animated sparking sprites when kidnapping Amy.

Special Stage

Sonic, are you alright...?

This is the first build with playable Special Stages, with a bevy of differences:

  • The UFOs are the same ones from some early screenshots, and look nothing like the final game's:
v0.51 Final
Sonic-CD-v0.51-UFO.gif Sonic-CD-Final-UFO.png
  • The blue UFO in the final that appears when the player has 20 seconds left does not appear in this prototype.
  • The game has a high chance of jumping to a black screen in most emulators if Sonic exits the level or touches the water. Touching the water also produces glitched tiles from the title card rather than the actual water splash graphics.
    • If the game doesn't crash, the results screen will show up with all Time Stones collected, but no score will be given. No music or sound effects play, either. This can frequently happen on real hardware.
  • The oil slicks from earlier builds are present, but don't function. The speed boosters don't work, either.
  • Sonic controls very differently compared to later builds and the final game: He doesn't run unless the player presses B, and pressing Down will not make him slow down; only letting go of B does.
  • Rings and other objects (such as the Power Sneakers) aren't present. The ring counter instead increments every 3 frames.

Unused Graphics

Artwork Description
Some kind of demo mode text?
Text that reads "PRESS START", loaded within the Special Stage VRAM.