Act Transition Upon Falling (S1)

This is a tutorial for going to a different act upon falling. I discovered that copying and editing SBZ2's Boundary_Bottom code can work for any level.


Let's get started.


For this tutorial we will do Act transition form GHZ2 to GHZ3.


1. Open up Sonic1.asm and go to your Boundary_Bottom code.


2. Now change your all of it to this:



Boundary_Bottom:
cmpi.w #$501,($FFFFFE10).w ; is level SBZ2 ?


bne.w GHZ_Check ; if not, kill Sonic


bra.s Load_SBZ3


GHZ_Check:


cmpi.w #$1,($FFFFFE10).w ; is level GHZ2 ?


bne.w KillSonic ; if not, kill Sonic


clr.b ($FFFFFE30).w ; clear lamppost counter


addq.b #1,($FFFFFE12).w ; add 1 to number of lives


move.w #$2,($FFFFFE10).w ; set level to GHZ3


rts


Load_SBZ3:


cmpi.w #$2000,($FFFFD008).w


clr.b ($FFFFFE30).w ; clear lamppost counter


move.w #1,($FFFFFE02).w ; restart the level


move.w #$103,($FFFFFE10).w ; set level to SBZ3 (LZ4)


rts



It's pretty self-explanatory but I will explain it.



Boundary_Bottom:
cmpi.w #$501,($FFFFFE10).w ; is level SBZ2 ?


bne.w GHZ_Check ; if not, kill Sonic


bra.s Load_SBZ3



This just checks if your level is SBZ2 and if so go to SBZ3.



GHZ_Check:
cmpi.w #$1,($FFFFFE10).w ; is level GHZ2 ?


bne.w KillSonic ; if not, kill Sonic


clr.b ($FFFFFE30).w ; clear lamppost counter


addq.b #1,($FFFFFE12).w ; add 1 to number of lives


move.w #$2,($FFFFFE10).w ; set level to GHZ3


rts



If it is not SBZ2 it will check for GHZ2 and if so go to GHZ3 (upon adding lives or else you will lose a life).


If neither levels it will kill Sonic.



Load_SBZ3:
cmpi.w #$2000,($FFFFD008).w


clr.b ($FFFFFE30).w ; clear lamppost counter


move.w #1,($FFFFFE02).w ; restart the level


move.w #$103,($FFFFFE10).w ; set level to SBZ3 (LZ4)


rts



Self-explaining.

 

You need to state that this is for sonic 1, of course I know but others may not at first. The problem with this alone if I remember correctly, is that if you have pits in the layout then falling say, in a pit half way through the level will send you to ghz3 which you only want for at the end or whatever. May want to mention this and provide a solution, you could set an unused ram adress say in Obj3A(end of act), then compare it in the Boundary_Bottom routine.

Code:

GHZ_Check:

  cmpi.w #$1,($FFFFFE10).w ; is level GHZ2 ?

  bne.w KillSonic ; if not, kill Sonic

  cmpi.w #$1,($????????).w ; is this set to 1 ? (Set the unused ram adress to 1 somewhere in Obj3A)

  bne.w KillSonic ; if not, kill Sonic

  clr.b ($FFFFFE30).w ; clear lamppost counter

  addq.b #1,($FFFFFE12).w ; add 1 to number of lives

  move.w #$2,($FFFFFE10).w ; set level to GHZ3

  rts