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SCHG How-to

Prevent SCZ Tornado spin dash death

From Sonic Retro

(Original guide by Esrael)

In Sky Chase Zone, it is possible to spin dash off from the Tornado, and fall to your death. One can argue that this is undesirable. Apparantly, SEGA felt the same way, as they fixed this in the Sonic Compilation REV 02 version of Sonic 2. Follow this guide to apply the same fix to your hack.

Find:

  loc_3A7DE:
   ......

        bsr.w   JmpTo27_SolidObject
        bsr.w   loc_3AE3A
        move.b  objoff_2E(a0),d0
        move.b  status(a0),d1
        andi.b  #8,d0    ; <---------- Change this line 
        andi.b  #8,d1    ; <---------- Change this line 
        eor.b   d0,d1
        move.b  d1,objoff_2E(a0)
        lea     (MainCharacter).w,a1 ; a1=character
        move.w  x_pos(a1),d1
        move.w  (Camera_X_pos).w,d0
        move.w  d0,(Camera_Min_X_pos).w

Change #8 to #1 and you can do spindash in Tornado.

  loc_3A7DE:
   ...... 

        bsr.w   JmpTo27_SolidObject
        bsr.w   loc_3AE3A
        move.b  objoff_2E(a0),d0
        move.b  status(a0),d1
        andi.b  #1,d0    ; <---------- Change this line 
        andi.b  #1,d1    ; <---------- Change this line 
        eor.b   d0,d1
        move.b  d1,objoff_2E(a0)
        lea     (MainCharacter).w,a1 ; a1=character
        move.w  x_pos(a1),d1
        move.w  (Camera_X_pos).w,d0
        move.w  d0,(Camera_Min_X_pos).w

One complaint you might have with this fix, is how the Tornado moves around the screen. It doesn't move very fluidly. So... its up to you to decide whether you'd like it not to be possible to fall off the plane, OR if you'd like everything to move more smoothly. For that reason, this is arguably more of a design choice, rather than a bug.

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 Spin Dash Code and Add Spin Dash Speeds | 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
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
Adding Features
Create Insta-kill and High Jump Monitors | Create Clone and Special Stage Monitors | Port Knuckles
Sound Features
Port Sonic 1 Sound Driver | Port Sonic 2 Clone Driver | Port Sonic 3 Sound Driver | Expand the Music Index to Start at $00 (Sonic 2 Clone Driver Version)
Extending the Game
Extend the Level Index Past $10 | Extend the Level Select | Extend Water Tables | Add Extra Characters | Free Up 2 Universal SSTs