Fix Blue Knuckles
From Sonic Retro
(Original guide by Tamkis)
(Additional and optional steps by AlexShx)
- 1 Who is Blue Knuckles: the bug explained
- 2 Making Blue Knuckles selectable
- 3 Fixing bugs
- 4 Unfixed bugs
- 5 Optional steps
Who is Blue Knuckles: the bug explained
Most people do not know, but in S3&K, there is a “hidden character” that is “unlockable” via Game Genie/Action Replay codes. This hidden character is Blue Knuckles. He is more than a palette change of the normal Red Knuckles; actually, he is identified internally as the character used for values greater than 3 for the variable player_mode. This variable, as the name states, determines what character(s) are in the game. The values are as follows:
- #0. Sonic & Tails
- #1. Sonic alone
- #2. Tails alone
- #3. Red Knuckles
- #4+.Blue Knuckles
The problem with making Blue Knuckles a playable character, however, is that he is not blue in the Special Stages, and most of his level events fail to work. In the Special Stages, he transforms into Sonic (lol). These errors happen, because Sega, in the asm code of S3&K (sonic3k.asm), mostly used comparison statements such as this:
cmpi.w #3,(Player_mode).w bne.s [label]
The label jumped to in statements like that would do something specific for when the player_mode is NOT 3 (Red Knuckles). Blue Knuckles is player_mode ID #4, so, with that statement, the game would goto the label meant for Sonic &/or Tails player modes, which is not what we want. We want Blue Knuckles to do the code after the bne.s, which is meant for Red Knuckles. This guide will fix statements of this format
The other comparison statement that is causing problems is in this format:
cmpi.w #3,(Player_mode).w beq.s [label]
If player_mode is #3 (Red Knuckles), the game will jump to a label for special processing for Knuckles events. If player_mode is NOT #3 (Red Knuckles), then the game will execute code for Sonic &/or Tails. Since Blue Knuckles (ID #4) is NOT ID #3, the game will execute Sonic &/or Tails code for Blue Knuckles, which is not what we want. We want Blue Knuckles to execute code for Red Knuckles. This guide will also fix statements of this format.
Making Blue Knuckles selectable
However, before we fix level events and other similar things for Blue Knuckles, let us make him a character that can be selected through ordinary means, without GG/AR codes. First, let us make him a selectable character in the Save Screen.
In the sonic3k.asm file in your S3&K .svn disasm, goto label SaveScreen_MainLoop / loc_C802 It should look something like this:
; loc_C802 SaveScreen_MainLoop: move.b #$1E,(V_int_routine).w jsr (Wait_VSync).l addq.w #1,(Level_frame_counter).w jsr (Process_Sprites).l move.w (Camera_X_pos_copy).w,d0 neg.w d0 move.w d0,(H_scroll_buffer+2).w jsr (Render_Sprites).l lea (Normal_palette_line_3+$2).w,a0 moveq #$E,d0 move.w ($FFFFE666).w,d1 addq.w #1,d1 cmpi.w #3,d1 bcs.s + moveq #0,d1
addq.w #1,d1 cmpi.w #3,d1
addq.w #1,d1 cmpi.w #4,d1 ; Blue Knuckles Fix: Now character #4 is the highest selectable
Then, goto label Obj_SaveScreen_NoSave_Slot / Obj_SaveScreen_D30C It should look something like this:
Obj_SaveScreen_NoSave_Slot: move.b #$F,$1D(a0) move.w ($FFFFEF4C).w,d0 addq.w #3,d0 move.b d0,$22(a0) tst.b ($FFFFEF4B).w bne.s loc_D396
addq.w #4,d0 ; Blue Knuckles Fix: No Save Slot - Now character #4 is the highest selectable
Afterwards, go to subprgm sub_D6D0; it should look like this:
sub_D6D0: moveq #0,d2 tst.w ($FFFFB07A).w bne.s loc_D6FA move.b (Ctrl_1_pressed).w,d1 lsr.w #1,d1 bcc.s loc_D6EE moveq #$5B,d2 addq.w #1,d0 cmpi.w #3,d0 bls.s loc_D6FA moveq #0,d0 bra.s loc_D6FA ; ---------------------------------------------------------------------------
cmpi.w #4,d0 ; Blue Knuckles Fix: Save Slot Update Character - Now character #4 is the highest selectable
Furthermore, goto label loc_D6EE. It should look like this:
loc_D6EE: lsr.w #1,d1 bcc.s loc_D6FA moveq #$5B,d2 subq.w #1,d0 bpl.s loc_D6FA moveq #3,d0
moveq #4,d0 ; Blue Knuckles Fix: Save Slot Update Character - Reset character to #4 if below #0 (negative)
Those modifications changed the max player_mode for the Save Screen, from #3 (Red Knuckles) to #4 (Blue Knuckles). Note that Blue Knuckles’ picture in the Save screen shows part of the “Del” sign seen when deleting a save, instead of a picture of a blue Knuckles. You will have to repoint manually the art to a suitable picture for blue knuckles. Use SonMapED and modify General\Save Menu\Map - Save Screen General.asm
Level Select Screen
Next, we will fix the character select for the Level Select screen. This character selection is done by pressing C on the level select screen. Pressing C will increment the player_mode. As before, we will change the max character from #3 (Red Knuckles) to #4 (Blue Knuckles).
There is only on step to fix it here. Goto loc_7F46. It should look like this:
loc_7F46: btst #5,(Ctrl_1_pressed).w beq.s locret_7F60 addq.w #1,(Player_option).w cmpi.w #4,(Player_option).w bcs.s locret_7F60 move.w #0,(Player_option).w
cmpi.w #4,(Player_option).w bcs.s locret_7F60
cmpi.w #5,(Player_option).w ; Blue Knuckles Fix: 04 is the highest selectable player_option blo.s locret_7F60 ; Used mnemonic "blo" instead of "bcs" - if player_option is lower than 5 don't reset to 0
Note: you can make Blue Knuckles available only in the Level Select Screen.
Now that Blue Knuckles is available for selection by normal means, we still have to fix all of his level events and other bugs. To do so, we will have to fix the player_mode comparison statements that were shown before. Search for every instance of “cmpi.w #3, (player_mode).w”:
- If the statement afterwards is “beq.s [label]”, change it to “bhs.s [label]”. (Branch if Higher or Same, the assembler will convert it to “bcc.s” when assembling)
- If the statement afterwards is “bne.s [label]”, change it to “blo.s [label]”. (Branch if LOwer than, the assembler will convert it to “bcs.s” when assembling)
If you did all of the replacements correctly, all of the level events and most other things for Blue Knuckles will work. But wait! In replacing ALL of those conditional statements, you inadvertently made player #4 (Blue Knuckles) red and fixed the bugs that made him blue! The following steps will restore the bugs that made player #4 blue.
Goto the following labels and revert what you changed back to the original code (i.e. change “bhs.s [label]” to “beq.s [label]” and “blo.s [label]” to “bne.s [label]”),
The labels, and what reverting the code back does:
- loc_61BE - Makes player #4 blue above water.
- loc_7A18 - Makes player #4 blue underwater.
- loc_8284 - Makes player #4 blue in Special Stages.
- loc_55C84 - Makes player #4 blue when entering the pyramid after SOZ miniboss.
If you did that step and all of the other steps right, you should now be able to select Blue Knuckles from the Save and Level Select Screens. Most of the bugs involving Blue Knuckles should be fixed now too.
Additional step 1: Fix End of Level Signpost
Now, as soon as we can, we have to fix the end of level signpost graphic for Blue Knuckles. This is as easy as "weird".
Go to FrameArray_EndSign, change this:
FrameArray_EndSign: dc.b 0, 0, 1, 2
FrameArray_EndSign: dc.b 0, 0, 1, 2, 2, 2, 2, 2 ; Character shown per ID: 00 - Sonic, 01 - Sonic, 02 - Tails, 03 - Knuckles, 04to07 - Blue Knuckles (Knuckles with blue palette)
Done. This loads and displays the variant #2 of the End Signpost instead of a null one, and since Knuckles' palette is blue, the displayed character will be Blue Knuckles.
Additional step 2: Revert to blue palette after Super/Hyper Transformation
Ok, now we need to fix Super/Hyper Blue Knuckles reverting back in Red to his "normal form". This happens because he uses the "Red" Knuckles' palette transition when reverting back to "normal form".
Go to SuperHyper_PalCycle_Revert / loc_37EE:
It should look like this:
; loc_37EE: SuperHyper_PalCycle_Revert: ; runs the fade in transition backwards cmpi.w #2,(Player_mode).w ; If Tails or Knuckles, branch, making this code Sonic-specific bhs.s SuperHyper_PalCycle_RevertNotSonic ; run frame timer subq.b #1,(Palette_timer).w ...
Ok, now change this:
; loc_37EE: SuperHyper_PalCycle_Revert: ; runs the fade in transition backwards cmpi.w #2,(Player_mode).w ; If Tails or Knuckles, branch, making this code Sonic-specific bhs.s SuperHyper_PalCycle_RevertNotSonic (loc_3820 in older disassemblies) ; run frame timer
; loc_37EE: SuperHyper_PalCycle_Revert: ; Runs the fade-in transition backwards cmpi.w #4,(Player_mode).w ; Check if character is Blue Knuckles beq.s SuperHyper_PalCycle_RevertSonic ; If character is Blue Knuckles branch to Sonic's reverting palette transition cmpi.w #2,(Player_mode).w ; If Tails or Knuckles, branch, making this code Sonic-specific bhs.s SuperHyper_PalCycle_RevertNotSonic ; (doesn't need to be changed as "Blue Knuckles' code" branched before) SuperHyper_PalCycle_RevertSonic: ; Apply for Sonic and Blue Knuckles ; run frame timer
Now Super/Hyper Blue Knuckles uses Super/Hyper Sonic's "reverting" transition wich makes him blue (and pretty) again after Super/Hyper form.
Unfortunately Blue Knuckles has some bugs yet to be fixed:
- He is messed up in the Slot Bonus Stage. See optional steps for hotfix
- Blue Super/Hyper Knuckles turns Red, but at least reverts Blue. See optional steps for fast fix or complete fix
How to prevent Blue Knuckles from accessing the Slot Bonus Stage (hotfix)
This surely isn't the best way to do it, but in this case bugged is way worse than nothing.
Just go to loc_2D47E and change this:
loc_2D47E: ... beq.s loc_2D506 move.b #2,(Special_bonus_entry_flag).w move.w #$1500,d1 ...
loc_2D47E: ... beq.w loc_2D506 ; (word used instead of short: jump distance too big) move.b #2,(Special_bonus_entry_flag).w move.w #$1500,d1 ; Load the Slot Bonus Stage cmpi.w #4,(Player_mode).w ; Check if player is Blue Knuckles bne.s .notBlueKnuckles ; Skip if not Blue Knuckles move.w #$1400,d1 ; Load Pachinko instead of Slot for Blue Knuckles .notBlueKnuckles: ...
As you see, this forces Blue Knux to enter Pachinko instead of Slot Bonus. You can use $1300 to load the Gumball Machine instead...or any stage or even code you want, at your own risk.
How to "Fix" Super/Hyper Blue Knuckles using Super/Hyper Sonic's palette cycles (fast fix)
In my case, since I don't want to make Super/Hyper Blue Knuckles appear like a "bad copy" of his famous red brother nor create a custom palette cycle, I figured out how to make his palette flash like Sonic's, fixing the "Blue Super/Hyper Knuckles turns Red" bug listed above in a cool and easy way.
Go to SuperHyper_PalCycle_Normal / loc_3854:
; loc_3854: SuperHyper_PalCycle_Normal: cmpi.w #2,(Player_mode).w ; If Tails... beq.w SuperHyper_PalCycle_NormalTails cmpi.w #3,(Player_mode).w ; ...or Knuckles, branch, making this code Sonic-specific bhs.w SuperHyper_PalCycle_NormalKnuckles tst.b (Super_Sonic_Knux_flag).w ; If Hyper Sonic, branch bmi.s SuperHyper_PalCycle_HyperSonic
Ok, now revert "bhs.w" to "beq.w". Change this:
beq.w SuperHyper_PalCycle_NormalKnuckles ; Super/Hyper Blue Knuckles now uses Super/Hyper Sonic's PalCycle (reverted Blue Knuckles Fix "bhs")
Note that this code changes only the color of Super/Hyper Blue Knuckles, this means that it doesn't add Hyper Sonic "Flashing Stars".
How to Fix Super/Hyper Blue Knuckles using a custom palette cycle
If you want Super/Hyper Blue Knuckles to be more "original" instead, you could create a different palette cycle for Super and Hyper Blue Knuckles by just messing around with the SuperHyper_PalCycle / SuperSonic_PalFlash subroutine, at label SuperHyper_PalCycle_NormalKnuckles / loc_393C.
The cycle that overrides palette on every frame is in that section and the palettes the code overwrites are at the bottom of the subroutine: you could just add a palette array by creating a copy of PalCycle_SuperHyperKnuckles / AnPal_SuperSonic_6, renaming it PalCycle_SuperHyperBlueKnuckles and editing every line to make Super/Hyper Blue Knuckles similar to "Super/Hyper Knuckles but blue"; just like this:
... PalCycle_SuperHyperKnucklesRevert: dc.w $64E,$20C,$206 ; Super/Hyper Blue Knuckles cycle PalCycle_SuperHyperBlueKnuckles: ; New palette cycle for Super/Hyper Blue Knuckles dc.w $BGR,$BGR,$BGR ; Frame 0 dc.w $BGR,$BGR,$BGR ; Frame 3 dc.w $BGR,$BGR,$BGR ; Frame 6 dc.w $BGR,$BGR,$BGR ; Frame 9 dc.w $BGR,$BGR,$BGR ; Frame C - 12 dc.w $BGR,$BGR,$BGR ; Frame F - 15 dc.w $BGR,$BGR,$BGR ; Frame 13 - 18 dc.w $BGR,$BGR,$BGR ; Frame 16 - 21 dc.w $BGR,$BGR,$BGR ; Frame 19 - 24 dc.w $BGR,$BGR,$BGR ; Frame 1C - 27
Make sure you replace every "BGR" with a valid Mega Drive palette color entry suitable for your Super/Hyper Blue Knuckles. Colors should be chosen wisely with PalCycle_SuperHyperKnuckles / AnPal_SuperSonic_6 taken as example.
Than just go to SuperHyper_PalCycle_NormalKnuckles / loc_393C and change this:
; loc_393C: SuperHyper_PalCycle_NormalKnuckles: ... ; increment palette frame and update Knuckles' palette lea (PalCycle_SuperHyperKnuckles).l,a0 move.w (Palette_frame).w,d0 ...
; loc_393C: SuperHyper_PalCycle_NormalKnuckles: ... ; increment palette frame and update Knuckles' palette lea (PalCycle_SuperHyperKnuckles).l,a0 ; Set to load Knuckles' palette cycle cmpi.w #4,(Player_mode).w ; Check if player is Blue Knuckles bne.s .notBlueKnuckles ; If not Blue Knuckles branch lea (PalCycle_SuperHyperBlueKnuckles).l,a0 ; set to load Blue Knuckles' palette cycle .notBlueKnuckles: ; Apply selected palette cycle move.w (Palette_frame).w,d0 ...
And finally, the last edit: this is mandatory if you don't want Blue Knuckles to briefly flash yellow before reverting to normal. Undo the reverting to blue step and go back to PalCycle_SuperHyperBlueKnuckles. Add this line under the palette array you just built:
PalCycle_SuperHyperBlueKnucklesRevert: ; Restore original Blue knuckles' palette dc.w $E66,$C42,$822 ; Sonic's palette line, offset $4-$6-$8
Last step. Go to SuperHyper_PalCycle_RevertKnuckles. Change this:
SuperHyper_PalCycle_RevertKnuckles: lea (PalCycle_SuperHyperKnucklesRevert).l,a0 bra.w SuperHyper_PalCycle_Apply
SuperHyper_PalCycle_RevertKnuckles: lea (PalCycle_SuperHyperKnucklesRevert).l,a0 ; Set to load Knuckles normal colors cmpi.w #4,(Player_mode).w ; Check if player is Blue Knuckles blo.s .notBlueKnuckles ; If not Blue Knuckles (or character 4+) branch lea (PalCycle_SuperHyperBlueKnucklesRevert).l,a0 ; Set to load Blue Knuckles normal colors (Sonic's palette line, offset $4-$6-$8) .notBlueKnuckles: ; Apply selected colors bra.w SuperHyper_PalCycle_Apply
And there you have it! A true Super/Hyper form for our beloved Blue Knuckles.
(Anyways) Now you can enjoy your new “Character”!
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