Sonic CD (2011)

Sonic CD from 2011 is a remake of the 1993 version.

Unused Menu Features
Left next to another unused menu selection (below), this appears to have been a cut feature from the Android and iOS versions, most likely putting touch controls to use. Unused because, technically, D-Pad's your only option. While "Final Fever" is the title of the Japanese final boss theme, Taxman (the lead developer) stated that during development this Final Fever was to be the name of a new boss stage, although it was cut due to Sega wishing to remain faithful to the original game. As this text was found among what seems to be an early Stage Select, it is safe to assume it used to represent this cut boss. A sprite of Sonic most notably used during the Sega CD BIOS boot. As it is present next to Sonic's sprite for the character select screen, it is safe to assume this once occupied that slot before the newer sprite took his place.

Unused Sprites
Interestingly, while all of Sonic's unused sprites were removed from this port, Tails got his own unused animation based on one of Sonic's! The default icon for sprites in the Retro Engine's Scene Editor, usually used for objects that aren't seen/spawned. Just your usual ? placeholder. Not much else to see here. The image that occupied the Exit selection of the Time Attack screen in the Sega CD and 1996 PC versions. Oddly, this can be seen in the Xbox 360 version by pressing B to exit Time Attack, then pressing A to select any Special Zone just before the transition to the main menu. The level the player goes to is the hidden eighth Special Stage, with the giant Eggman/Robotnik head in the background.

Sonic and Tails' animation files (as well as their Mini versions) have unused animations that are mostly empty, except for Sonic's Corkscrew H, which actually has 12 frames of seemingly random parts of his sprite sheet, and were clearly made for an earlier version of the sheet.

'''Sliding Gliding Drop Gliding Stop Climbing Ledge Pull Up    Corkscrew H    Corkscrew V    Finish Pose'''

Unused Animation Rotation Flags
All the animation files have an unused value, dubbed "Full Engine Rotation" it lets the object using the animation file to rotate to any angle, not the 45-degree angles of the normal game, there is also a value that does the same as the default flag, the only difference is that it doesn't use rotated sprites and instead lets the engine rotate them to multiples of 45 degrees.

Unused Manual Sprites
The final game uses PNGs in .arc files, but there exists .gif versions of the pictures the manual uses, these are however, used in the mobile version as that version doesn't use .arc files. There are also PNG files for the sprites with Metal that are used in the manual.

Unused Pictures
An unused logo from Onan Games. There doesn't appear to be any connection between Onan Games and this port, but Onan Games, what little they're known for, usually port games. This information in mind, it could be assumed either they ported Sonic CD to PC, and weren't credited, or they were originally planned to port it but they ended up getting someone else to port it. It was probably the former. Unused simple wallpaper. Leftover demo screen from the Xbox 360 version.

Desert Dazzle
According to Taxman, Desert Dazzle was a new level he was working on that ended up being cut for time and authenticity reasons. The level's graphical design was heavily influenced by the Sand Shower Zone mockup image that was sent to magazines to promote Sonic the Hedgehog 2 in the early 1990s. The image on the left can be accessed by entering the Sound Test code PCM: 32, DA: 8. After viewing the image, you'll be taken to the Stage Select with Tails as your character. In the January 2014 update, stage assets for both Desert Dazzle and Final Fever were released, complete with full level maps. The video Sonic CD- Desert Dazzle (Alpha PC Port) is a mod of the PC version, which replaces Palmtree Panic's tiles and level layout with Desert Dazzle's. Because the stage was never finalized, no badniks or gimmicks were ever implemented. The default background music for both soundtracks is the Time Attack theme (track 33). Desert Dazzle would finally see the light of day in Sonic Mania, with its tiles re-purposed for Mirage Saloon Zone.

Retro Engine Developer Features
Set byte 0xCCB (offset CAB in HxD) in GameConfig.bin to 1 to access this menu from the pause screen.

There is a mode in Sonic CD (RSDKv2) that allows the game to read the object scripts as .txt files instead of the bytecode files, this is activated when the game can't find the file "Data/Scripts/Bytecode/GlobalCode.bin" (or "Data/Scripts/Bytecode/GS000.bin" on PC).

Regional Differences
In all Western releases, the non-highlighted palette of the menu text is a grayish hue. The Japanese version has a white hue for this text, as well as the expected translated text.