Sonic the Hedgehog CD prototype 510, referred to as CD Sonic the Hedgehog on the title screen, is the earliest known prototype of the game Sonic the Hedgehog CD for Mega CD produced on May 10th, 1992. This prototype features a prominent "Comin' Soon" screen. It was 'discovered' 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 play the first three: Palmtree Panic, Collision Chaos and Tidal Tempest. The rest can be viewed through the Level Select. This prototype contains several differences from the final game.
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