Sonic the Hedgehog CD prototype 510, referred to as CD Sonic the Hedgehog on the title screen, is among the first prototypes of the game Sonic the Hedgehog CD for Mega CD. This prototype was leaked by a group of fans called Sega Extreme in the summer of 2000. The game contains all the stages of the final game, but in a normal playthrough the player can only see the first three: Palmtree Panic, Collision Chaos and Tidal Tempest. The rest can be viewed through the Level Select. This prototype deviates in many ways from the final game.
• A 3D SEGA logo displays while the SEGA sound plays.
• The Title Screen is very different:
- 320x224 mode is used, as opposed to 256x224 mode. - The SEGA logo is golden. - On the ribbon the title CD Sonic The Hedgehog appears. - The clouds appear on the left, the mountain with the face of Dr. Eggman is larger, the menu is top-down and there are fewer mountains. - Also appearing in the credits is Keiko Utoku, a singer in the Japanese and European Opening.
• In the Time Attack screen, the exit logo displays an image of the Little Planet and the chain attaching it to the mountain with Eggman's face
• At the end of a level Sonic looks completely different.
• The original game had 3 additional power-ups:
- Super Monitor: Sonic has increased speed and an invincibility shield. It has a red "S" symbol. - Blue Belt: Functions identically to the Super Monitor. Has the image of a blue ring. - Freeze time: Has the image of a clock. This does not work correctly, but its role was to freeze time for a few seconds.
• Amy Rose has larger eyes and quills.
• After completing the first 3 levels, screen that says "COMIN' SOON" is displayed.
• The lives counter is slightly higher than normal, and there are no zeros in the SCORE and RINGS counter.
• The flowers that come from each badnik are different.
• There are badniks in the Good Future of every zone.
• Tracks 2 to 24 and 32 are the same, but without fadeout.
• Track 25 and 26: Early version of the title song, very different from the final version. It is a shortened version of Sonic - You Can Do Anything.
• Track 28: Super Shoes song. A rather strange remix of "Sonic - You Can Do Anything".
• Track 31: Special Stage song. It is longer than the original. It lasts 4 and a half minutes, and is considerably more "remix" than the original.
Title screen and opening
• The home video is transmitted on a screen in a fund brick. Each brick has the name SONIC inscribed on it.
• Also under the screen are the Japanese symbols 开発画面. They translate to development screen.
• The showing Little Planet chained to the ground is played in reverse.
• The video in the beta has a speed of 50Hz.
• A scene from the mountains with Eggman's face and the attached chain is shown, but is not included in the final version.
• The Opening Song glitches throughout, with some bugs and breaks during play.
The Special Stage design is not 100% completed, although in the demo of the game, one of them is displayed while showing a text at the top that reads: "The programmer has a nap. Hold out! Programmer!"
Some info taken from SonicRetro.