63 lines
2.4 KiB
NASM
63 lines
2.4 KiB
NASM
; =============================================================================
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; Book of Secrets (Reveal Secrets with Book of Mudora)
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; Makes BG2 Disappear when pressing X+R
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; Based on the Parallel Worlds feature
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;
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; Bank 0x3C used for whole code
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; Layer Flags: xxxsabcd (i count BG from 1 to 4 - MathOnNapkins RAM-Map counts from 0 to 3)
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; s - Sprite layer enabled
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; a - BG4 enabled
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; b - BG3 enabled
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; c - BG2 enabled
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; d - (BG1 disabled) --> only works properly if the room uses the feature "BG2 on Top"
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;
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; Written by XaserLE
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; Edited by scawful
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; =============================================================================
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; =============================================================================
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; code that branches behind the dungeon map load if player didn't press X
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org $0288FD
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BRA $1C ; make it always branch, so map isn't loaded anymore
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; =============================================================================
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; long subroutine that is executed every frame
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org $068365
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JSL LinkItem_SecretsBook ; overwrite it (originally JSL $099F91)
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; =============================================================================
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; go to expanded space to write our routine
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; (keep EveryFrame.asm in mind for the right adresses)
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; org $3CA600
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org $2B8000
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LinkItem_SecretsBook:
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{
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LDA $1B ; load data that tells us whether we are in a building or not
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AND #$01 ; are we in a building?
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BEQ .end ; if not, don't use the x-button-secret
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; ----------
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LDA $7EF34D ; load book of mudora slot
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CMP #$01 ; do we have the moon pearl?
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BNE $0F ; if not, go to enable BG2
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LDA $F2 ; load unfiltered joypad 1 register (AXLR|????)
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AND #$50 ; delete all bits except those for X and R
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SEC ; set carry for the following subtraction
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SBC #$50 ; X+R button pressed? (if yes, zero flag is set)
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BNE $06 ; if not, go to enable BG2
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LDA $1C ; load layer flags
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AND #$FD ; disable BG2 (0xFD = 11111101)
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BRA $04 ; go to store layer flags
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LDA $1C ; load layer flags
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ORA #$02 ; enable BG2 (0x02 = 00000010)
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STA $1C ; store layer flags
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; ----------
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.end
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JSL $099F91 ; at least execute original code
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RTL
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}
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pushpc
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; ============================================================================= |