Fix the EHZ Deformation bug

(Original guide by qiuu)

In Sonic 2 is in EHZ a small deformation bug, the lowest two layers don't scroll as they are not affected by the deformation code:

To fix this, go to SwScrl_EHZ:. Scroll down until you see SwScrl_RippleData:. Above it you should have this piece of code:

	move.w	#($B4)/12-1,d1 ; $B4 bytes
-	move.w	d4,(a1)+
	move.w	d3,(a1)+
	move.w	d4,(a1)+
	move.w	d3,(a1)+
	move.w	d4,(a1)+
	move.w	d3,(a1)+
	swap	d3
	add.l	d0,d3
	add.l	d0,d3
	add.l	d0,d3
	swap	d3
	dbf	d1,-

	rts

Copy and paste this code twice into it:

	move.w	d4,(a1)+
	move.w	d3,(a1)+

In the end it should look like this:

	move.w	#($B4)/12-1,d1 ; $B4 bytes
-	move.w	d4,(a1)+
	move.w	d3,(a1)+
	move.w	d4,(a1)+
	move.w	d3,(a1)+
	move.w	d4,(a1)+
	move.w	d3,(a1)+
	swap	d3
	add.l	d0,d3
	add.l	d0,d3
	add.l	d0,d3
	swap	d3
	dbf	d1,-
	move.w	d4,(a1)+
	move.w	d3,(a1)+
	move.w	d4,(a1)+
	move.w	d3,(a1)+

	rts

And that's it! Now it should look fixed:

Sonic 2 Beta

This bug can also be fixed in the Sonic 2 Beta.

Just replace the code with this:

	move.w	d4,(a1)+
	move.w	d3,(a1)+
	move.w	d4,(a1)+
	move.w	d3,(a1)+
	move.w	d4,(a1)+
	move.w	d3,(a1)+
	swap	d3
	add.l	d0,d3
	add.l	d0,d3
	add.l	d0,d3
	swap	d3
	dbf	d1,loc_61B2
	move.w	d4,(a1)+
	move.w	d3,(a1)+
	move.w	d4,(a1)+
	move.w	d3,(a1)+

	rts

SCHG How-To Guide: Sonic the Hedgehog 2 (16-bit)
Fixing Bugs
Fix Demo Playback \| Fix a Race Condition with Pattern Load Cues \| Fix Super Sonic Bugs \| Use Correct Height When Roll Jumping \| Fix Jump Height Bug When Exiting Water \| Fix Screen Boundary Spin Dash Bug \| Correct Drowning Bugs \| Fix Camera Y Position for Tails \| Fix Tails Subanimation Error \| Fix Tails' Respawn Speeds \| Fix Accidental Deletion of Scattered Rings \| Fix Ring Timers \| Fix Rexon Crash \| Fix Monitor Collision Bug \| Fix EHZ Deformation Bug \| Correct CPZ Boss Attack Behavior \| Fix Bug in ARZ Boss Arrow's Platform Behavior \| Fix ARZ Boss Walking on Air Glitch \| Fix ARZ Boss Sprite Behavior \| Fix Multiple CNZ Boss Bugs \| Fix HTZ Background Scrolling Mountains \| Fix OOZ Launcher Speed Up Glitch \| Fix DEZ Giant Mech Collision Glitch \| Fix Boss Deconstruction Behavior \| Fix Speed Bugs \| Fix 14 Continues Cheat \| Fix Debug Mode Crash \| Fix 99+ Lives \| Fix Sonic 2's Sega Screen
Design Choices
Remove the Air Speed Cap \| Disable Floor Collision While Dying \| Modify Super Sonic Transformation Methods & Behavior \| Enable/Disable Tails in Certain Levels \| Collide with Water After Being Hurt \| Retain Rings When Returning at a Star Post \| Improve the Fade In\Fade Out Progression Routines \| Fix Scattered Rings' Underwater Physics \| Insert LZ Water Ripple Effect \| Restore Lost CPZ Boss Feature \| Prevent SCZ Tornado Spin Dash Death \| Improve ObjectMove Subroutines \| Port S3K Rings Manager \| Port S3K Object Manager \| Port S3K Priority Manager \| Edit Level Order with ASM‎ \| Alter Ring Requirements in Special Stages \| Make Special Stage Characters Use Normal DPLCs \| Speed Up Ring Loss Process \| Change spike behaviour in Sonic 2
Adding Features
Create Insta-kill and High Jump Monitors \| Create Clone and Special Stage Monitors \| Port Knuckles
Sound Features
Expand Music Index to Start at $00 \| Port Sonic 1 Sound Driver \| Port Sonic 2 Clone Driver \| Port Sonic 3 Sound Driver \| Port Flamewing's Sonic 3 & Knuckles Sound Driver \| Expand the Music Index to Start at $00 (Sonic 2 Clone Driver Version) \| Play Different Songs Per Act
Extending the Game
Extend the Level Index Past $10 \| Extend the Level Select \| Extend Water Tables \| Add Extra Characters \| Free Up 2 Universal SSTs

SCHG How-To Guide: Sonic 2 Nick Arcade (16-bit)
Fixing Bugs
Fix EHZ Deformation Bug
Design Choices
Add final spindash to Sonic 2 Beta \| How to port paralax plouds to the Nick Arcade prototype

SCHG How-To Guide: Sonic 2 Beta (16-bit)
Fixing Bugs
Fix EHZ Deformation Bug
Design Choices
Add final spindash to Sonic 2 Beta

|Fix the EHZ Deformation bug]]

SCHG How-to

Fix the EHZ Deformation bug

From Sonic Retro

Sonic 2 Beta