- Back to: Sonic the Hedgehog CD (Mega-CD prototype; 1993-06-21)/Comparisons.
General
The v0.51 prototype is the first known build to include playable Special Stages. However, step into the water, run out of time or destroy all the UFOs and the game will fade to a black screen and hang. Because of this, the player can't access more than the first Special Stage legitimately. Hidden in this prototype are stages 2 through 7, as well.
Sonic usually starts the Special Stage from the top right-hand corner, meaning in the first stage, he has to negotiate some grass. There is no introductory animation, and Sonic will only start running if the user presses and holds 
(which also means it's possible to stop by letting go of ). The player gets 99 seconds to complete the stage (versus 100) and the Ring counter continously increases, looping back to zero after hitting 250.
The UFOs have completely different graphics in this build. They also flash different colours, and don't dispense rewards when destroyed.
Dash Zones don't work at all, which means it's impossible for Sonic to get to full speed.
Hit a Chopper Block and Sonic will collapse into a pile of broken graphics, only able to move forward until he hits something else.
As was seen briefly in the 510 and 512 prototypes, oil litters most of the Special Stages, but it has no effect on Sonic at all. Due to the way the Special Stages work in Sonic CD (i.e. to have any chance of winning, the player will spend most of their time jumping and therefore not be on the ground), the player is unlikely to collide with them in the earlier rounds.
Stage 2
Stage 3
Stage 4
Stage 5
Stage 6
Stage 7
References
(which also means it's possible to stop by letting go of 
