Add Extra Item Options for 2 Player VS Mode

Tutorial by E-122-Psi, but largely (as in almost completely) compromised of coding provided by Cinossu.

This was largely done in the Xenowhirl edit, though the variations in GitHub shouldn't be too hard to find.

The default 2 Player VS items options are bit too limited and randomised, so let's try adding some more options to benefit those with muscle memory.

Adding "Normal Items" Mode

To add the option in the menu, first go to word_917A and change the Two_Player_Items flag to 2FF instead of 1FF (meaning a flag of now 0 (random), 1 (teleport) and 2 (normal)):

word_917A:
    dc.w $2FF
    dc.w Player_option    ; 1
    dc.w $2FF    ; 2
    dc.w Two_player_items    ; 3
    dc.w $7FFF    ; 4
    dc.w Sound_test_sound    ; 5

Now go to off_92BA. Add 3 items instead of 2 in off_92EA and add your byte for the option.

off_92BA:
    dc.l byte_97CA
    dc.w $4192
    dc.w 3
    dc.l byte_982C
    dc.w $4592
    dc.w 3
    dc.l byte_985E
    dc.w $4992
    dc.w 3
off_92D2:
    dc.l byte_97DC
    dc.l byte_97FC
    dc.l byte_980C
off_92DE:
    dc.l byte_97EC
    dc.l byte_97FC
    dc.l byte_981C
off_92EA:
    dc.l byte_983E
    dc.l byte_984E
    dc.l byte_Fixed
off_92F2:
    dc.l byte_9870

Now find the menu text for the options bytes and the one you've made, with the desired text.

    ; options screen menu text

byte_97CA:    dc.b $10,"* PLAYER SELECT *"
byte_97DC:    dc.b  $E,"SONIC AND MILES"
byte_97EC:    dc.b  $E,"SONIC AND TAILS"
byte_97FC:    dc.b  $E,"SONIC ALONE    "
byte_980C:    dc.b  $E,"MILES ALONE    "
byte_981C:    dc.b  $E,"TAILS ALONE    "
byte_982C:    dc.b $10,"* VS MODE ITEMS *"
byte_983E:    dc.b  $E,"ALL KINDS ITEMS"
byte_984E:    dc.b  $E,"TELEPORT ONLY  "
byte_Fixed:    dc.b  $E," NORMAL ITEMS  "
byte_985E:    dc.b $10,"*  SOUND TEST   *"
byte_9870:    dc.b  $E,"      0"
        dc.b $10,"       "

Now you should have your new option available, but it won't do anything, just give you teleport monitors. To give it a unique function go to the monitor contents routine (Obj2E) and make a branch in loc_12868 or Obj2E_Init depending on disassembly:

loc_12868:
    addq.b    #2,routine(a0)
    move.w    #$8680,art_tile(a0)
    bsr.w    Adjust2PArtPointer
    move.b    #$24,render_flags(a0)
    move.b    #3,priority(a0)
    move.b    #8,width_pixels(a0)
    move.w    #-$300,y_vel(a0)
    moveq    #0,d0
    move.b    anim(a0),d0
    tst.w    (Two_player_mode).w
    beq.s    loc_128C6
    cmp.w    #2,(Two_player_items).w    ; Is it fixed items?
    beq.s    loc_128C6
    move.w    (Timer_frames).w,d0
    andi.w    #7,d0            ;7 means 8 different items
    addq.w    #1,d0            ;add 1 to prevent getting static monitor
    tst.w    (Two_player_items).w    ; Are monitors set to teleport only?
    beq.s    loc_128AC
    moveq    #8,d0            ;force contents to be teleport

loc_128AC:
    cmpi.w    #8,d0            ;teleport?
    bne.s    loc_128C2
    move.b    (Update_HUD_timer).w,d1
    add.b    (Update_HUD_timer_2P).w,d1
    cmpi.b    #2,d1            ;is either player finished?
    beq.s    loc_128C2
    moveq    #7,d0            ;give invincibility instead

loc_128C2:

    move.b    d0,anim(a0)

loc_128C6:            ; Determine correct mappings offset.
......

With your new second flag branched over all the two player data edits, your monitors should now work normally....well almost.

Since two player by default displays a question mark, that is now loaded as the content when broken (which gives you nothing). You'll have to fix it the monitors to load their normal mappings in 2-player.

Go to loc_126E2 or Obj26_Init depending on your disassembly, and now add a check for the new items flag to branch over the ? icon implement:

loc_126E2:
    move.b    #$46,collision_flags(a0)
    move.b    subtype(a0),anim(a0)
    tst.w    (Two_player_mode).w
    beq.s    obj_26_sub_2
    cmp.w    #2,(Two_player_items).w    ; Is it fixed items?
    beq.s    obj_26_sub_2
    move.b    #9,anim(a0)    ;show ? screen

And hurrah, you should now have a fully functioning 'normal' item option mimicing one player layout. If to a fault, since this setup obviously means there are no Tails 1-up monitors, only Sonic ones according to normal Sonic and Tails mode.

Now there are different ways of getting around this:

1. Make separate object edits for the 2P levels, and then editing them in a level editor to have an even balance of Sonic and Tails monitors.

2. Edit the monitor layouts, to give a 1-up to the character regardless. In which case, find the pointer list for the monitor contents (Obj2E again):

; ===========================================================================
sonic_1up:
    cmp.w    #2,(Two_player_items).w    ; Is it fixed items?
    bne.s    sonic_1up_1P
    cmpa.w    #MainCharacter,a1
    bne.s    tails_1up
sonic_1up_1P:
    addq.w    #1,($FFFFFEF4).w
    addq.b    #1,(Life_count).w
    addq.b    #1,(Update_HUD_lives).w
    move.w    #$98,d0
    jmp    (PlayMusic).l    ; Play extra life music
; ===========================================================================
tails_1up:
    cmp.w    #2,(Two_player_items).w    ; Is it fixed items?
    bne.s    tails_1up_1P
    cmpa.w    #Sidekick,a1
    bne.s    sonic_1up
tails_1up_1P:
    addq.w    #1,($FFFFFEF6).w
    addq.b    #1,(Life_count_2P).w
    addq.b    #1,(Update_HUD_lives_2P).w
    move.w    #$98,d0
    jmp    (PlayMusic).l    ; Play extra life music
; ===========================================================================

And now the monitor should give a 1-up to whoever breaks it in Normal Items mode, regardless of icon. Of course the monitor will still display Sonic's icon regardless, so you may want to edit the sprite art to have something more ambiguous.