Some fans have gone so deep into the game (Sonic CD), they found a little extra peek at something ultimately cut from the final release:
"It" is called Desert Dazzle zone, according to developer Christian Whitehead. Speaking about it on the Sonic Retro forums, Whitehead said it was part of a planned extra level for the game, but never made it:
Christian Whitehead wrote:Basically, earlier on in the remake’s development there were 2 new levels: Desert Dazzle & Final Fever (another boss)
Neither level was fully complete, and we had to make the call whether or not to go ahead and finalize them. Sonic Team felt the game should not deviate too far from it’s original form, and in retrospect it was for the best since we had a lot of other work to do anyway.
I left this image in since it’s quite a groovy looking Zone, and it also serves as a way for you to get to the stage select as Tails.
Already, there are calls to add the Dust Hill inspired stage down the road as paid DLC.
