|title=Sonic the Hedgehog CD (prototype 712)
Sonic CD Build 712 is a prototype of Sonic CD for the Mega CD, named because the CD dates itself to July 12, 1993. This is a later build of the game that is near completion, but is still unfinished in places and has some differences. Game copy provided by Phugolz.
Despite the Title Screen having the proper title, the game is still referred as "CD SONIC THE HEDGEHOG" internally.
Save files created by this prototype can be used in the final game, and vice versa.
Debug mode can be used in Time Attack. It was disabled in the final to prevent cheating.
The robot transporter in the Present doesn't appear to have degraded as much as it has in the final.
Invisible objects that catapult Sonic into ball form (usually found in tubes) will become visible with shield, invincibility or time warp graphics if Sonic has any of those items in effect.
The "S" and Clock monitors have been removed aside from a secret room in Palmtree Panic 3, but the Blue Ring monitor can still be found in a few sporadic locations throughout the game. They also have their effects changed somewhat:
The Clock monitor, when placed with Debug Mode, causes other monitors to stop blinking.
The Blue Ring monitor now functions like an invisible shield, allowing you to take a hit without losing your rings. It can also stack with a regular shield.
Getting all the Time Stones doesn't automatically destroy all robot transporters and thus won't change all futures to Good Futures.
The game-ending "I'm outta here!" easter egg now causes an instant Game Over as intended, but the camera will still follow Sonic as he jumps off the stage, dying from reaching the bottom of the stage.
The player will always get a bad ending even if the the player has destroyed every robot transporter in the game or collected all the Time Stones. The good ending has been implemented though, and can be viewed in Visual Mode.
The ending FMVs have no music or sound effects, and don't display the "TRY AGAIN/YOU'RE TOO COOL!" messages or the "Presented by SEGA" text at the end.
The jump sound doesn't work properly in normal stages. It works in the Special Stage, though.
The Super Peel-Out doesn't play any sound effects, but the Spin Dash does.
Destroying a badnik plays a different sound rather than the traditional badnik explosion sound.
When you gain an extra life, instead of Sonic saying "Yes!", he says "Yeah!".
Destroying the robot transporter in the Past doesn't play a sound after the explosion.
The goal signpost doesn't make a sound when passing it.
Pausing the game does not pause the music; it simply mutes it.
The time warp sound is different from both the 510 prototype and the final, this time playing a CD audio track that would go unused in the final. It is track #33, whereas it would be track #2 in the final.
The Special Stage demo that plays by waiting at the Title Screen isn't a demo at all; it is fully controllable.
The starting points for all Special Stages are in odd places, such as on the far corner on the dirt that slows you down or partially inside a bumper, instead of starting on the road.
Sonic doesn't strike a pose when the Special Stage begins.
The oil slicks are present but don't affect game play in the Special Stage.
When a UFO is destroyed, the UFO counter doesn't count down until the UFO stops exploding. In the final, it counts down immediately after smashing the UFO.
When all UFOs are destroyed, the Time Stone doesn't wait until the camera finishes turning around Sonic and drops as the camera starts turning. It also doesn't make a sound.
The different RAM Data screen.
Menu navigation on the title screen is inverted.
The preview for Special Stage 6 in the Time Attack menu doesn't animate.
The RAM Data screen has very different visuals.
The RAM Data menu is not fully functional and has some bugs that would be fixed in the final:
You cannot copy your save file to the Sega CD's internal RAM if a RAM cartridge is not present or there isn't already a Sonic CD save file copy in the internal RAM.
Erasing your save file doesn't appear to work.
You can't seem to replace your save file with one saved in storage.
The D.A. Garden is called "Sound Test" on the title screen.
Exiting the D.A. Garden will lock up the game.
The Visual Mode screen does not have background music.
"Opening" is misspelled as "Openning" on the Visual Mode screen.
The pencil test hasn't been implemented and cannot be viewed yet. Selecting it in the Visual Mode will just play the opening FMV.
There is no rock at the end of Act 2 to stop you in your tracks.
The background parallax in the Past glitches out at the top of the stage near the end of each Act.
The mini bumpers that surround the yellow point cups make the same sound as the large bumpers when collided with.
PCM-based sound effects such as the bumpers don't work in Act 3.
The outdoor background in the Good Future is still different. The sky is black, the mountains are darker, and the foliage is less refined.
The end of the upward transport tube near the robot transporter in Act 2 has a group of large platforms at the end, stopping you from flying right into the transporter. They were removed in the final.
The bouncy floor doesn't make any sounds.
The angel statue in the Past of Act 1 is a solid object and doesn't give you rings.
Act 3 has an arrangement of rings before the boss that spell out "CD". This arrangement is replaced with a pyramid of rings in the final.
The capsule at the end of Act 3 is sunken into the floor a bit.
Parts of the foreground in the Past are blue instead of yellow.
The sky in the Bad Future is constantly flashing red.
There is no spring in the way of the goal in Act 2.
The boss music doesn't start during the intro to the Metal Sonic race. It instead begins when the race starts and plays throughout.
The background parallax in the Good Future of Act 3 glitches out near the end of the race.
The Level Select screen is the same as the one in the 510 prototype.
On the title screen, press on the first controller, then press on the second controller when NEW GAME or CONTINUE appears. A black screen with a list of numbers and letters corresponding to various levels and events appears just as it looked in the 510 prototype. Make a selection and press to enter it. Completing any level or attempting time travel will take you back to the title screen.
Sound Effects Test
On the title screen, press on the first controller, then press on the second controller when NEW GAME or CONTINUE appears. Press to play the currently selected sound, and to exit.
Press on the second controller at any time during gameplay to enable/disable Debug Mode.
: Toggle normal and debug mode.
: Advance forward through the debug object list.
: Advance backwards through the debug object list.
: Place the selected object at the current coordinates.