Information: This is a patch that allows you to see under layers using specific buttons combinations.
Rom: ALTTP (US), without header; pc w/o header ALTTP (US)
Screenshot:



Ups Patch: http://bszelda.zeldalegends.net/stuff/Con/lens_of_truth.zip

Additional info: This is for making BG2 disappear when pressing X and R together (parallel worlds x button secret). But only if you have the Mirror in the inventory (suitable to revert it into Lens of Truth).

Code Addresses: main code at $1FA600

ASM:

Code:


;WRITTEN: by XaserLE
;THANKS TO: -MathOnNapkins' Zelda Doc's
; -wiiqwertyuiop for his Zelda Disassembly

; Layer Flags: xxxsabcd (i count BG from 1 to 4 - MathOnNapkins RAM-Map counts from 0 to 3)
; s - Sprite layer enabled
; a - (BG4 enabled)??
; b - BG3 enabled
; c - BG2 enabled
; d - (BG1 enabled)??

; NOTE BY Puzzledude, remove the 3 lines, which have "added" on the end, to disable bg2 all the time (no Mirror needed)


;header
lorom

ORG $0288FD ; go to the code that branches behin the dungeon map load if player didn't press X
BRA $1C ; make it always branch, so map isn't loaded anymore

ORG $068365 ; go to a originally JSL that is executed every frame
JSL $3FA600 ; overwrite it (originally JSL $099F91)

ORG $03FA600 ; go to expanded space to write our routine

LDA $1B ; load data that tells us whether we are in a building or not
AND #$01 ; are we in a building?
BEQ $1A ; if not, don't use the x-button-secret, edited from 12 to 1A
LDA $F2 ; load unfiltered joypad 1 register (AXLR|????)
CMP #$50 ; X and R buttons pressed?
BNE $06 ; if not, go to enable BG2
LDA $7EF353 ; load ram mirror slot, added
CMP #$02 ; compare to value 02 (have mirror is 02, no mirror is 00), added
BNE $06 ; if not value 02, go to enable BG2, added
LDA $1C ; load layer flags
AND #$FD ; disable BG2 (0xFD = 11111101)
BRA $04 ; go to store layer flags
LDA $1C ; load layer flags
ORA #$02 ; enable BG2 (0x02 = 00000010)
STA $1C ; store layer flags

JSL $099F91 ; at first execute original code

RTL