Some changes and fixes for Sonic 2

Nicely done! :o I never noticed this until you brought it up.


Edit: Thought I'd whip an en explanation that you can paste into your post.


When the boss is defeated, it falls apart. If it is facing left, it falls apart properly. However, if it is facing the other way, the pieces still fall as if it was facing the other way. This behaviour is obviously wrong. The following code checks which way he is facing, and properly calls for the right routine so that he falls apart properly!

 

I like the crossover drills

 

Someone with wiki skills ought to put this on SCHG. Boggles my mind how I never noticed this @_@

 

I wont be able to until tomorrow, but I can do it.
Provided it isn't already done by then...

I remember Esreal pointing this out in his Delta hack thread, and I thought he meant something else entirely... I feel stupid now. LOL

 

I see you're joining me on the bug hunting =P

Except for the ARZ boss bug, I've fixed all these already. Nice find and will apply the ARZ bug today. Cheers for that, mate.


For ARZ boss bug, keep reading this post.
For MCZ boss and 5 CNZ boss bugs, click here
For CPZ boss bug, click here



EDIT: Looking at your ARZ boss fix, I will say, there is another "quicker" and "shorter" way to fix the ARZ boss bug. This can be followed for the other bosses as well. It's just quicker on the processor rather than it branching to a subroutine and such. Just thought I'd let you know about it in case.



Change:

Code (ASM):

1. loc_30850:
2.     cmpi.w  #$78,($FFFFF75C).w
3.     bgt.s   return_3088A
4.     subi.w  #1,y_radius(a0)
5.     move.l  objoff_3A(a0),d0
6.     move.w  objoff_2E(a0),d1

To this:

Code (ASM):

1. loc_30850:
2.     cmpi.w  #$78,($FFFFF75C).w
3.     bgt.s   return_3088A
4.     subi.w  #1,y_radius(a0)     ; Make hammer fall to the left
5.     btst    #0,render_flags(a0) ; Is Eggman facing left?
6.     beq.s   +           ; Yes?  Branch and continue
7.     addi.w  #2,y_radius(a0)     ; So he's facing right?  Make hammer fall to the right instead
8. +
9.     move.l  objoff_3A(a0),d0
10.     move.w  objoff_2E(a0),d1

This works also, and it's just quicker and it save space as it doesn't have to contain a subroutine. You can do something similar to this with the other bosses.

 

Either way is good. Just saying the way I did it will be quicker and will save you some ROM space (okay, hardly much space, but every little helps, right? =P )


You couldn't find my other fixes, because I hadn't posted them. I was saying that to do it my way for MCZ and CNZ boss, just follow the same principle I showed you for ARZ boss. But I'll post them here now if you like =)




MCZ boss


Change all this:

Code (ASM):

1. loc_31358:
2.     cmpi.w  #$78,($FFFFF75C).w
3.     bgt.s   return_313C4
4.     subi.w  #1,status(a0)
5.     move.l  objoff_3A(a0),d0
6.     move.w  objoff_2E(a0),d1
7.     addi.w  #$38,objoff_2E(a0)
8.     ext.l   d1
9.     asl.l   #8,d1
10.     add.l   d1,d0
11.     move.l  d0,objoff_3A(a0)
12.     move.w  objoff_3A(a0),routine(a0)
13.     cmpi.w  #$6F0,routine(a0)
14.     blt.s   loc_31392
15.     move.w  #0,objoff_2E(a0)
16.  
17. loc_31392:
18.     addi.w  #1,x_vel(a0)
19.     move.l  objoff_34(a0),d0
20.     move.w  objoff_30(a0),d1
21.     addi.w  #$38,objoff_30(a0)
22.     ext.l   d1
23.     asl.l   #8,d1
24.     add.l   d1,d0
25.     move.l  d0,objoff_34(a0)
26.     move.w  objoff_34(a0),y_vel(a0)
27.     cmpi.w  #$6F0,y_vel(a0)
28.     blt.s   return_313C4
29.     move.w  #0,objoff_30(a0)
30.  
31. return_313C4:
32.     rts

To this:

Code (ASM):

1. loc_31358:
2.     cmpi.w  #$78,($FFFFF75C).w
3.     bgt.w   return_313C4
4.     subi.w  #1,status(a0)       ; Make drill face to the left
5.         btst    #0,render_flags(a0)     ; Is Eggman facing left?
6.         beq.s   +                       ; Yes?  Branch and continue
7.         addi.w  #2,status(a0)       ; So he's facing right?  Make drill face to the right instead
8. +
9.     move.l  objoff_3A(a0),d0
10.     move.w  objoff_2E(a0),d1
11.     addi.w  #$38,objoff_2E(a0)
12.     ext.l   d1
13.     asl.l   #8,d1
14.     add.l   d1,d0
15.     move.l  d0,objoff_3A(a0)
16.     move.w  objoff_3A(a0),routine(a0)
17.     cmpi.w  #$6F0,routine(a0)
18.     blt.s   loc_31392
19.     move.w  #0,objoff_2E(a0)
20.  
21. loc_31392:
22.     addi.w  #1,x_vel(a0)        ; Make drill fall to the left
23.         btst    #0,render_flags(a0)     ; Is Eggman facing left?
24.         beq.s   +                       ; Yes?  Branch and continue
25.         subi.w  #2,x_vel(a0)        ; So he's facing right?  Make drill fall to the right instead
26. +
27.     move.l  objoff_34(a0),d0
28.     move.w  objoff_30(a0),d1
29.     addi.w  #$38,objoff_30(a0)
30.     ext.l   d1
31.     asl.l   #8,d1
32.     add.l   d1,d0
33.     move.l  d0,objoff_34(a0)
34.     move.w  objoff_34(a0),y_vel(a0)
35.     cmpi.w  #$6F0,y_vel(a0)
36.     blt.s   return_313C4
37.     move.w  #0,objoff_30(a0)
38.  
39. return_313C4:
40.     rts

Done




CNZ boss


Change all this:

Code (ASM):

1. loc_31EAE:
2.     cmpi.w  #$78,($FFFFF75C).w
3.     bgt.s   return_31F22
4.     subi.w  #1,status(a0)
5.     move.l  objoff_3A(a0),d0
6.     move.w  objoff_2E(a0),d1
7.     addi.w  #$38,objoff_2E(a0)
8.     ext.l   d1
9.     asl.l   #8,d1
10.     add.l   d1,d0
11.     move.l  d0,objoff_3A(a0)
12.     move.w  objoff_3A(a0),routine(a0)
13.     cmpi.w  #$6F0,routine(a0)
14.     blt.s   loc_31EE8
15.     move.w  #0,objoff_2E(a0)
16.  
17. loc_31EE8:
18.     cmpi.w  #$3C,($FFFFF75C).w
19.     bgt.s   return_31F22
20.     addi.w  #1,x_vel(a0)
21.     move.l  objoff_34(a0),d0
22.     move.w  objoff_30(a0),d1
23.     addi.w  #$38,objoff_30(a0)
24.     ext.l   d1
25.     asl.l   #8,d1
26.     add.l   d1,d0
27.     move.l  d0,objoff_34(a0)
28.     move.w  objoff_34(a0),y_vel(a0)
29.     cmpi.w  #$6F0,y_vel(a0)
30.     blt.s   return_31F22
31.     move.w  #0,objoff_30(a0)
32.  
33. return_31F22:
34.     rts

To this:

Code (ASM):

1. loc_31EAE:
2.     cmpi.w  #$78,($FFFFF75C).w
3.     bgt.w   return_31F22
4.     subi.w  #1,status(a0)       ; Make catcher face to the left
5.         btst    #0,render_flags(a0)     ; Is Eggman facing left?
6.         beq.s   +                       ; Yes?  Branch and continue
7.         addi.w  #2,status(a0)       ; So he's facing right?  Make catcher face to the right instead
8. +
9.     move.l  objoff_3A(a0),d0
10.     move.w  objoff_2E(a0),d1
11.     addi.w  #$38,objoff_2E(a0)
12.     ext.l   d1
13.     asl.l   #8,d1
14.     add.l   d1,d0
15.     move.l  d0,objoff_3A(a0)
16.     move.w  objoff_3A(a0),routine(a0)
17.     cmpi.w  #$6F0,routine(a0)
18.     blt.s   loc_31EE8
19.     move.w  #0,objoff_2E(a0)
20.  
21. loc_31EE8:
22.     cmpi.w  #$3C,($FFFFF75C).w
23.     bgt.s   return_31F22
24.     addi.w  #1,x_vel(a0)        ; Make catcher fall to the left
25.         btst    #0,render_flags(a0)     ; Is Eggman facing left?
26.         beq.s   +                       ; Yes?  Branch and continue
27.         subi.w  #2,x_vel(a0)        ; So he's facing right?  Make catcher fall to the right instead
28. +
29.     move.l  objoff_34(a0),d0
30.     move.w  objoff_30(a0),d1
31.     addi.w  #$38,objoff_30(a0)
32.     ext.l   d1
33.     asl.l   #8,d1
34.     add.l   d1,d0
35.     move.l  d0,objoff_34(a0)
36.     move.w  objoff_34(a0),y_vel(a0)
37.     cmpi.w  #$6F0,y_vel(a0)
38.     blt.s   return_31F22
39.     move.w  #0,objoff_30(a0)
40.  
41. return_31F22:
42.     rts

Done



Another CNZ boss BUG


As we're on fixing boss bugs, ever noticed the other 4 bugs on CNZ's boss? If not, read on. The very first hit on the CNZ boss, it will NEVER make the boss-hit sound. Also, you know Eggman normally shows his hurt face when you hit him? The very first hit, he delays showing his hurt face (about 2 seconds later after the first hit). Also, during his first hit, he will flash a lot longer, and until he stops flashing, you cannot hit him again!


So, that's the 4 bugs, all happening on the first hit:

• Never plays boss hit sound
• Eggman's hurt face delayed
• Eggman flashes a hell of a lot longer
• Because he flashes a lot longer, you cannot hit a second time for a while

The rest of the hits, he's fine though. To solve all these bugs, the fix is EXTREMELY simple =P




Go to "loc_31904:". You should see this near the middle of the coding:

Code (ASM):

1.     move.b  #$80,objoff_14(a0)

Delete it.

There, done.


Explaination

objoff_14 is part of the countdown timer. Normally, this timer is at 0. When you hit Eggman, the countdown timer is set to $30, then starts counting down. Whilst it's counting down, Eggman will flash. You cannot hit him whilst flashing (that's not a bug). At "loc_31CDC", it tests objoff_14 for 0. If not equal, it will branch away. NORMALLY, when you hit Eggman, as soon as you hit him, it will set objoff_14 to $30, play the sound and display Eggman's hurt face, and then countdown from $30. But because at "loc_31904" where Eggman is being created, it has set this timer to $80. So on the first hit, it's got a lot to countdown (until it reaches 0). Because of this, he flashes for AGES. And because of this, you cannot hit him a second time for a while. Because it's $80, it cannot branch to the playsound and set objoff_14 to $30. Eventually, it's counted down to 0, then he's fine the rest of the time.


At "loc_31C92", it compares the objoff_14 at $2F. If so, branch to display Eggman's hurt face. On the first hit, because it's counting down from $80, it takes ages to $2F, and that's why Eggman has a delay on showing his hurt face on the first hit.


Because we've deleted the command, objoff_14 is already set at 0. So, it is ready for action. So now, on the first hit, he will now play the sound and set the timer to $30, he will display his hurt face immediately (because it's only a byte away), and because it's counting down from $30, he will not flash as long, and you can get back to hitting him quicker. All 4 bugs, fixed!


Why the hell did they set objoff_14 to $80 when being created in the first place, I have no idea.


This may help you on your hack =)


Cheers,
redhotsonic

 

Did anyone ever make the CPZ boss's blue gunk able to hurt Sonic when he's ducking? I think there's something of a debate over whether it's intentional, muddied by the fact that it does hurt Tails and (I'm assuming) Knuckles, but anyway. It's (like most of them) not the kind of boss I think needs an easy method like that. :P

 

You're welcome. I'm glad I could be an assistance. Especially to you, Esrael.

Sure, there is an easy fix. I've applied it myself, and it seems to work. And it hasn't affected anything else. So, here goes.




CPZ boss bug


As many of you are aware, during the CPZ boss, when Eggman drops the blue gunge on you, if you are "ducking" you cannot get hurt, making it too easy to avoid Eggman's attacks.


Sonic unhurt from gunge



To fix this so you will get hurt whilst ducking, follow this.


Go to "loc_2E692:" and you'll see this:

Code (ASM):

1. loc_2E692:
2.     addq.b  #2,routine_secondary(a0)
3.     move.b  #$20,y_radius(a0)
4.     move.b  #$19,anim(a0)
5.     move.w  #0,y_vel(a0)
6.     movea.l objoff_34(a0),a1 ; a1=object
7.     movea.l $34(a1),a1
8.     btst    #2,$2D(a1)
9.     beq.s   loc_2E6CA
10.     bclr    #2,$2D(a1)
11.     move.b  #6,routine_secondary(a0)
12.     move.w  #9,objoff_2A(a0)

See that command?

Code (ASM):

1.     move.b  #$20,y_radius(a0)

Change #$20 to #$16. So you have this in the end:

Code (ASM):

1. loc_2E692:
2.     addq.b  #2,routine_secondary(a0)
3.     move.b  #$16,y_radius(a0)
4.     move.b  #$19,anim(a0)
5.     move.w  #0,y_vel(a0)
6.     movea.l objoff_34(a0),a1 ; a1=object
7.     movea.l $34(a1),a1
8.     btst    #2,$2D(a1)
9.     beq.s   loc_2E6CA
10.     bclr    #2,$2D(a1)
11.     move.b  #6,routine_secondary(a0)
12.     move.w  #9,objoff_2A(a0)

Done




Explanation

The gunge's y_radius is #$20. This is fine normally. But when Sonic "ducks", Sonic's y_radius is "shortened". So, now, when the gunge is falling and hits the ground, it actually doesn't touch Sonic.

Because we have "lowered" the gunge's y_radius, it's distance from the floor has grown just a little bit. Because of this, the gunge now falls down, just a little bit more, and because of this, it will now hit Sonic when he's "ducking". And it will still hurt Sonic in any other position also.




Something Cool for CPZ boss!

THIS IS JUST FOR LAUGHS, but I thought I'd share it anyway! Back at the label "loc_2E692:". See these two lines?

Code (ASM):

1.     btst    #2,$2D(a1)
2.     beq.s   loc_2E6CA

Comment them out! And everytime Eggman drops the gunge, this will happen!




Well, I found it funny =P

 

...That's a bug? That always seemed intentional. Hell, I found it cool that you could do that even.

 

Maybe it was intended when he drops the gunge over himself. It would likely be more complex to recognise when the player is directly beside Robotnik when it drops though.

 

"For fuck sake, RHS! Stop it with all these bug fixes!" Is what you lot are probably thinking =P


But as this subject seems to be on bosses, I thought I'd post another one here. Another ARZ glitch.




ARZ boss bug




With this boss, as soon as you're hurt, Eggman won't laugh instantly. Instead, he waits for you to hit the ground, then he laughs. Same goes for Tails. All the other boss, Eggman laughs instantly. So let's fix this.




Go to "loc_30770:" (part of the ARZ boss code) and you'll see this:

Code (ASM):

1. loc_30770:
2.     lea ($FFFFF740).w,a1
3.     move.b  #$31,3(a1)
4.  
5. loc_3077A:

Under the "move.b #$31,3(a1)", insert this line:

Code (ASM):

1.     move.b  #1,objoff_36(a0)    ; move 1 to checker

So you have something like this:

Code (ASM):

1. loc_30770:
2.     lea ($FFFFF740).w,a1
3.     move.b  #$31,3(a1)
4.     move.b  #1,objoff_36(a0)    ; move 1 to checker
5.  
6. loc_3077A:

Next, go to "loc_3075C:" and you'll see this:

Code (ASM):

1. loc_3075C:
2.     bsr.w   loc_3078E
3.     cmpi.b  #4,(MainCharacter+routine).w
4.     beq.s   loc_30770
5.     cmpi.b  #4,(Sidekick+routine).w
6.     bne.s   loc_3077A

After the "bsr.w loc_3078E" command, insert these two lines:

Code (ASM):

1.     tst.b   objoff_36(a0)       ; Is checker 0?
2.     bne.s   loc_3077A       ; If not, branch and do not check for Sonic/Tails hurt state

So you have something like this:

Code (ASM):

1. loc_3075C:
2.     bsr.w   loc_3078E
3.     tst.b   objoff_36(a0)       ; Is checker 0?
4.     bne.s   loc_3077A       ; If not, branch and do not check for Sonic/Tails hurt state
5.     cmpi.b  #4,(MainCharacter+routine).w
6.     beq.s   loc_30770
7.     cmpi.b  #4,(Sidekick+routine).w
8.     bne.s   loc_3077A

Next, go to "return_3078C:" and you'll see this:

Code (ASM):

1. return_3078C:
2.     rts

Change it to this:

Code (ASM):

1. return_3078C:
2.     cmpi.b  #$17,($FFFFF743).w  ; Has Eggman stopped laughing?
3.     bne.s   +           ; If not, branch
4.     clr.b   objoff_36(a0)       ; If so, clear checker, so Eggman can check to see if Sonic/Tails are hurt again
5. +
6.     rts

Done








Explanation

Most of you have probably noticed that Eggman didn't laugh instantly. BUT, did any of you notice that when hurt, Eggman's animation is actually frozen? Yup, that's right. Normally, his mustache is moving (due to wind I guess), but as soon as you're hurt, his mustache isn't moving anymore. He's frozen and until you hit the ground, he will remain that way. When you've hit the ground, he will then laugh, then carry on with his normal animations.


It's important to know, for this boss, the animations are working another way rather than they normally do. instead of "anim" being set, $FFFFF743 (or $FFFFF740+3) is being set. This RAM adress counts down every frame, to make Eggman animate. Every odd number dispalys one part of his anim, and every even number displays another part of his anim. His mustache for instance. Every odd number displays 1 part and every even displays another, making his mustache move.


Anyway, the reason for Eggman's animation freezing is because when Sonic/Tails gets hurt, their routine is set to 4 (hurt routine). Eggman checks this, and if hurt, move $31 to his animation. But at this moment in time, the RAM address CANNOT countdown. It tries to, but it can't. The reason why, is because as Sonic and tails are hurt, until they land on the floor, their routine will stay at 4. Because Eggman is continuously seeing them at routine 4, it constantly writes $31 to $FFFFF743. That's why the RAM cannot countdown. And because it's constantly at $31, it's only able to display one part of his animation, and that's why Eggman's anim is frozen.


As soon as Sonic/Tails lands, their routine is set back to normal. Eggman now stops writing $31 to $FFFFF743, letting the RAM address able to countdown, now displaying his laugh animation.



So, what have we done to fix this? We've added a new check using objoff_36(a0) (not used in ARZ boss so it's free to use). As soon as Sonic/Tails gets hurt, it now moves #1 to objoff_36(a0). We've added a check before the Sonic/Tails hurt check. If objoff_36(a0) is now equals 1, to branch away from the hurt check, leaving $FFFFF743 free to countdown. Eggman now displays his laugh instantly.

After Eggman's laugh, $FFFFF743 is set back to $17 and counts down again (Eggman's normal animation). We've done one more check to see if $FFFFF743 equals $17 and if so, to clear objoff_36(a0). Now that objoff_36(a0) is now 0 again, Eggman can now check to see when Sonic/Tails gets hurt again, and laugh when so.


Everything is fine once again!


Long explanation, eh? =P



redhotsonic

 

http://info.sonicret...uction_Behavior
http://info.sonicret...e_CNZ_boss_bugs
http://info.sonicret...attack_behavior
http://info.sonicretro.org/SCHG_How-to:Fix_ARZ_boss_sprite_behavior
God damn it RHS! LOL I kid, I like that you are pointing out these bugs.
And Esrael as well! Let's keep finding more. This is fun.

 

You guys are amazing! I really like these bug fixes. I have implemented a bunch in my ROM, mostly ones that I have found and fixed. However, lately I've been looking at posts about different bug fixes I wasn't aware of. These, for example, I didn't really notice until I saw this topic. I will gladly credit both Esrael and RHS when my work has been made public.

On a side note... although I personally don't believe in special labels for members (such as "Tech Member"), since Retro does it, I will gladly put this out there: RHS should be a tech member! Is anyone up stairs listening? This takes talent!

 

Preach on, brother... this, 1000x over.

 

This is clever, and makes perfect sense! I believe this behavior is definitely how it was originally planned.

And, by the way *bows to the master* I can't believe that you are actually back in here, after such a long time, Esrael! It was all thanks to you that I got into the fabulous world of Sonic hacking back then.

Thank you, my master!

 

I remember finding the graphics for that extra boss behaviour in the old "MD8123" Sonic 2 proto back in my "Knuckles Prower" days - I had no idea that the graphics existed in the final, or that code that referenced them was commented out, though! Amazing find, and great to see your tweak to return it to what was almost certainly the intended behaviour. = ) Never thought I'd see this in action!

One thing, though - the existing code seems to display the art slightly too far to the right for some reason. If you check out the old .GIF animation I made back when I originally found the graphics to show how it might look in action (currently viewable on the Sonic CulT S2 Proto Lost Sprites page), you can see that the graphics are actually designed to perfectly mask Robotnik's body, even including the small bits you can see through the shine in his Eggmobile's windscreen! For some reason though, the code you've found looks like it gets this alignment wrong by a few pixels - the whole graphic is 3 pixels too far to the right. Is there any way of shifting the goo-covered Robotnik sprite to the left by 3 pixels in order to fix this? = )