How to fix Tails' respawn speeds in Sonic 2 and S3K

How to fix Tails' respawn speeds


The problem





Bye, Tails! I'm leaving you behind.





Oh, Tails! You're back!





Keep up, Tails! Oh wait, you can't, you still think you're underwater!


The problem here is when you and Tails enter the water, your speed, acceleration and deceleration are decreased, to give you the underwater physics. The problem is, if you lose Tails when underwater, when he next respawns (in Sonic 2, he only respawns when you've come out of water), he will still have his underwater speeds. Hence why Tails suddenly cannot keep up. This bug only occurs when you lose Tails underwater, and his underwater speed will remain this way until he enters/exits water again (no matter how many times you lose him and he respawns).


The bug is NOT fixed in S3K either, but to fix it, you have to do an extra check, so follow the S3K fix.


The fix


Sonic 2


This can be done in Xenowhirl's 2007 disassembly or the SVN disassembly.


Go to "loc_1BC68:" and you'll see this:



loc_1BC68:
lea (Sonic_Stat_Record_Buf).w,a2


move.b 2(a2,d3.w),d2


andi.b #$D2,d2


bne.s return_1BCDE


or.w d0,d1


bne.s return_1BCDE


; etc...



Right after the 2nd "bne.s return_1BCDE" command, insert this:



move.w #$600,(Tails_top_speed).w ; set Tails' top speed
move.w #$C,(Tails_acceleration).w ; set Tails' acceleration


move.w #$80,(Tails_deceleration).w ; set Tails' deceleration



So, you have something like this:



loc_1BC68: ; Fix for Tails' underwater respawn
lea (Sonic_Stat_Record_Buf).w,a2


move.b 2(a2,d3.w),d2


andi.b #$D2,d2


bne.s return_1BCDE


or.w d0,d1


bne.s return_1BCDE


move.w #$600,(Tails_top_speed).w ; set Tails' top speed


move.w #$C,(Tails_acceleration).w ; set Tails' acceleration


move.w #$80,(Tails_deceleration).w ; set Tails' deceleration


; etc...



Done


Sonic 3 and Knuckles


This can be done in SVN disassembly.


Go to "loc_13CD2:" and you'll see this:



loc_13CD2:
lea (Stat_table).w,a2


move.b 2(a2,d3.w),d2


andi.b #$80,d2


bne.s loc_13D42


or.w d0,d1


bne.s loc_13D42


; etc...



Right after the 2nd "bne.s loc_13D42" command, insert this:



btst #6,$2A(a0) ; test underwater flag
bne.s +


move.w #$600,($FFFFFEC0).w ; set Tails' top speed


move.w #$C,($FFFFFEC2).w ; set Tails' acceleration


move.w #$80,($FFFFFEC4).w ; set Tails' deceleration


+



So, you have something like this:



loc_13CD2: ; Fix for Tails' underwater respawn
lea (Stat_table).w,a2


move.b 2(a2,d3.w),d2


andi.b #$80,d2


bne.s loc_13D42


or.w d0,d1


bne.s loc_13D42


btst #6,$2A(a0) ; test underwater flag


bne.s +


move.w #$600,($FFFFFEC0).w ; set Tails' top speed


move.w #$C,($FFFFFEC2).w ; set Tails' acceleration


move.w #$80,($FFFFFEC4).w ; set Tails' deceleration


+


; etc...



Done


The bug explained


Now, when you lose Tails, he goes through lots of commands to move him about and to respawn him on certain conditions. BUT, none of these commands reset Tails' speeds. Because of this, when Tails respawns, he has the exact same speeds as when you lost him. So, if you lose him underwater, when he respawns, he will still have underwater speeds. So, all we've done here is added the command to reset his speeds. So...


In Sonic 2, all we've done is set Tails to use his normal speeds no matter what when he respawns. This is fine because he only respawns when you're not in water, so he will always be out of water when he arrives. So we want his normal speed.


In Sonic 3 and Knuckles, we have to do a check first to see if Tails is respawning in water or not. If not, do not bother resetting the speeds because he's going to spawn in water. On the other hand, if not in water, it will reset to his normal speeds because he's going to respawn out of water.


That's it.


Enjoy


redhotsonic

 

Nice to see another good guide from you, redhotsonic!


I've never noticed this bug in S2/S3K before, because Tails always seemed to behave silly to me. =P


Anyways, good to see one more bug found and fixed.


Also, there is a small mistake in your guide (in S3K section):



btst #6,$2A(a0) ; unset underwater flag



Comment says 'unset', while command says 'test'.

 

Small typo, lol. At least it doesn't affect the code itself, but I will change it anyway =P

 

Bumped for your attention, in case anyone has applied this to their hack.


Both S2 and S3K guides have been slightly edited. The commands to reset Tails' speeds have been moved a bit lower. That way, his speeds only get written once, rather than over and over and over until he stops flying. That way, this won't take as much processing time.