Decomp: https://github.com/Rubberduckycooly/Sonic-CD-11-Decompilation
Mods used:
Sonic CD Separated Past Themes - SoN1c2001, US Past Themes by KingMeteorStudios
Higher Quality JP/US Music Mod - Darkskull Dawn Zenith
Restart Special Stages/Time Attack - MegAmi
1996 PC Title Screen - RetroForever
Collision Chaos is Sonic CD's version of Spring Yard. Spring Yard was after Marble Zone, wasn't it?
Sonic CD at one point did have its own take on Marble Zone, the cut "R2". A snippet of it can be seen in the animated ending montage, and it's known to feature rainbow waterfalls. It was apparently removed due to not being great to play, but supposedly, bits of it were merged into Tidal Tempest and the Wacky Workbench easter egg room.
At this time, SuperFreaksDev has 531 views for Sonic CD spread across 43 videos. The game makes up 1 hour of published video on his channel, roughly 2.40% of Sonic CD content that SuperFreaksDev has uploaded to YouTube.