Under the Surface of Classic Sonic

All about programming, unused content, and more in the Classic Sonic games!

[Under the Surface of Classic Sonic @SCDDeconstruct]

@Conradd72371258 Pretty much.

[Under the Surface of Classic Sonic @SCDDeconstruct]

There exists a collision bug where the check used to prevent Sonic from clipping on top of a surface he's too far below from isn't done if he's moving horizontally in the air. This can easily be seen if you put a solid object on a top solid surface and hit it from the bottom.

[Under the Surface of Classic Sonic @SCDDeconstruct]

@Conradd72371258 Hard to say. Chaotix uses a different engine from the mainline games, and it's not nearly as documented as them.

[Under the Surface of Classic Sonic @SCDDeconstruct]

...and Sonic 3 & Knuckles.

[Under the Surface of Classic Sonic @SCDDeconstruct]

...and Sonic CD...

[Under the Surface of Classic Sonic @SCDDeconstruct]

@LittlePlanetCD If anyone is curious about how this jump works, check out this explanation. Note that the 2011 remake actually can't do this without modding it.
https://t.co/pLhL2JYJSy

[Under the Surface of Classic Sonic @SCDDeconstruct]

Here's a visualization/explanation of this in video form.

[Under the Surface of Classic Sonic @SCDDeconstruct]

@mothnaman @Needlen0se @ParapastaCD @LittlePlanetCD It should, yes. It's a direct port of the original assembly code, unlike the 2011 remake.

[Under the Surface of Classic Sonic @SCDDeconstruct]

12800 = 50 * 0x100

[Under the Surface of Classic Sonic @SCDDeconstruct]

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.

[Under the Surface of Classic Sonic @SCDDeconstruct]

(You can find the hack here: https://t.co/fJqR6zdvpN)

[Under the Surface of Classic Sonic @SCDDeconstruct]

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

[Under the Surface of Classic Sonic @SCDDeconstruct]

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.

[Under the Surface of Classic Sonic @SCDDeconstruct]

Here's the highlighted line from the decompilation:
https://t.co/fXN3TOp7e0

[Under the Surface of Classic Sonic @SCDDeconstruct]

I looked into this and saw from the decompilation that the stage ID check is messed up. The original Sega CD version checks if the stage is Palmtree Panic act 1 (zone ID 0, act ID 0), but the 90s PC port checks if the zone ID is 255 and if the act ID is 1...

[𝗠𝗲𝗹𝗹𝗼-𝗡𝗼𝘃𝗮 @Mellon_Nova]

@SCDDeconstruct For some reason the PC96 version doesn't disable the Signs in both Past and Future versions for the beginning portion

[Under the Surface of Classic Sonic @SCDDeconstruct]

@chrisprice @Mellon_Nova I actually might look deeper into this. I did notice that the 712 prototype had the same bugged special stage 1 background palette cycling as in the PC version...

[Under the Surface of Classic Sonic @SCDDeconstruct]

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?

[𝗠𝗲𝗹𝗹𝗼-𝗡𝗼𝘃𝗮 @Mellon_Nova]

@SCDDeconstruct Can also get to them utilizing the moving peelout glitch
Obviously still not intended, but still interesting