Under the Surface of Classic Sonic

12800 = 50 * 0x100

Here's a silly difference between the 510 and 0.28A (512) prototypes of Sonic CD. Special stage rings always appear in 510, but never in 0.28A. 0.28A added a ring count check, but only checked the top byte. As a result, they can only appear if the player has at least 12800 rings.

(You can find the hack here: sonicresearch.org/community/in...)

There's a ROM hack of Chaotix called Knuckles' Clackers by GenesisDoes that reimplements loops, and even uses the masking sprite... but it still illustrates the problematic nature of loops with the tethering mechanic.

Small fun fact, there's an unused sprite in the final build that would have acted as a sprite mask by drawing on top of the character sprites, but set to use a low priority color so that it would appear behind the loop, which is drawn by the Genesis.

Loops were planned on being implemented in Chaotix, even being present in prototypes... yeah, I can see why they were removed (footage provided by @mdtravis.bsky.social)

Seems like you can mess around with the peelout to get the collision to register, though.

I do know you can glitch the physics in the 3D loop to get you to into that area... maybe it's just a failsafe in case that section goes wrong? Can't say for sure, though.

No, you can't time travel in this area. In the present, the camera will refuse to go back once you've gone past it, and if you are in the past or future, time travel gets disabled.

Curiously, there's a couple of hidden springs around here as well, but they cannot be touched, because they are completely obscured by the ramp.

There's a hidden tunnel that can be found right towards the end of the 3D loop section at the beginning of Palmtree Panic act 1 that I'm not sure is even accessible via normal means. Anyone have any ideas?

The Metallic Madness act 2 demo was, indeed, rerecorded as well. The USA demo struggles while the Japanese demo gets quite a bit further ahead.

Left: Japan/Europe, Right: USA

The Metallic Madness act 2 demo was, indeed, rerecorded as well. The USA demo struggles while the Japanese demo gets quite a bit further ahead.

Left: Japan/Europe, Right: USA

The Tidal Tempest act 3 demo was also rerecorded. What I find peculiar is how whoever recorded the USA demo slowly walked to the boss while the Japanese demo caught up. Were they trying to eyeball the Japanese demo? I dunno...

Left: Japan/Europe, Right: USA

The Tidal Tempest act 3 demo was also rerecorded. What I find peculiar is how whoever recorded the USA demo slowly walked to the boss while the Japanese demo caught up. Were they trying to eyeball the Japanese demo? I dunno...

Left: Japan/Europe, Right: USA

Note the different timings. With the special stages, the demo ends when the controller data reaches an entry with the start button pressed. The normal stage demos are fixed at 2048 frames.

Special Stage 6
Left: NTSC, Right: PAL

In the PAL version of Sonic CD, the physics of Sonic were modified to more closely resemble the NTSC physics while at a lower frame rate. As such, separate demo controller data had to be recorded for the special stage demos.

Special Stage 1
Left: NTSC, Right: PAL

For some reason, the demo for Palmtree Panic act 1 was rerecorded for the USA release of Sonic CD. Here's a comparison showing the differences.

Left: Japan/Europe, Right: USA

Thanks for the 200 followers :)

Sorry that I've not been posting as much here. I admittedly don't really use Bluesky and I keep forgetting about this account. I should find the time to bring this account up to date.

This also doesn't apply to the special stages, but the special stages don't use separate files for the demos like the regular levels do, so there's not really anything to look into for that.

Note that you may find some parts of the level corrupted. This is because part of the level data is overwritten with the demo controller data, with the demo avoiding showing those corrupted parts.

bsky.app/profile/clas...

A few ways to play and see it:
1. Modify the disc image to set the byte at 0x2A75353 from 1 to 0 (712 prototype only)
2. Modify RAM in an emulator to set address 0xFF1581 to 0 (works in final)
3. Use PAR code FF1581:00 or Game Genie code AAL9-8AEB in an emulator (works in final)

Note this as well
bsky.app/profile/clas...

Additional fun fact: the sprite here was repurposed for the Backup RAM manager.

This is because the demo files that get run during the title screen were built at an earlier time than the normal stage files found on the disc. This pattern of the demos being from earlier builds is also found in the final game.

Thanks to c4/seafour4 on the Hidden Palace Discord server, a new prototype signpost sprite was discovered in the Palmtree Panic act 1 demo (DEMO11A.MMD) in the 712 prototype of Sonic CD, which was previously only seen in a magazine.

I think what's interesting about the "Player shock jump up" line is the fact they deliberately used the unsigned byte representation of -2 (0xFE) when setting Mario's Y speed...

Additionally, you can see the removed lines of code in the official All Stars source code!