; This code allows for a wall-jump in Metroid (NES)
; Copyright 2002-2005 Parasyte
; http://parasyte.panicus.org/
;
; The above copyright notice may not be removed or changed.
;
;
; Notes:
; Simply overwrite the data at file address 0x01CAD4 (48 bytes, max)
; with this code. Then set the hook by patching 0x01CC34 to 0xC4,0xCA


.org $CAC4		;assemble our code to run at this (CPU) address
.mem 8			;setup accumulator and index regs for NES code
.index 8


;--constants
BtnRight	= $01		;Joypad button definitions.
BtnLeft		= $02
BtnDown		= $04
BtnUp		= $08
BtnStart	= $10
BtnSelect	= $20
BtnB		= $40
BtnA		= $80

ItemBombs	= $01		;Item definitions
ItemHighJump	= $02
ItemLongBeam	= $04
ItemScrewAttack	= $08
ItemMaruMari	= $10
ItemVaria	= $20
ItemWaveBeam	= $40
ItemIceBeam	= $80


;--pointers
JoypadDown	= $12
Joypad		= $14

JumpSpeed	= $0308

ItemFlags	= $6878		;Items Samus has collected

DoJump		= $CD40		;Makes Samus Jump

WallToLeft	= $E880		;Checks for a wall to the left of Samus, returns result in C flag: Set = no, Clear = yes.
WallToRight	= $E88B		;Checks for a wall to the right of Samus, returns result in C flag: Set = no, Clear = yes.




;--Entry Point
; Inputs:	None
; Outputs:	None
; Description:	Checks if Samus is able to wall jump, performs action if possible.

	lda ItemFlags		;Does Samus have High Jump Boots?
	bit #ItemHighJump
	beq exit		;No? Exit!

	lda JoypadDown		;Is A button just pressed?
	bpl exit

	lda #BtnRight
	bit Joypad		;D-Pad Right held?
	beq +

	;Check if able to wall jump to the right.
	jsr WallToLeft
	bcs exit
	bcc ++

+	asl
	bit Joypad		;D-Pad Left held?
	beq exit

	;Check if able to wall jump to the left.
	jsr WallToRight
	bcs exit

++	ldx JumpSpeed		;Is Samus in a slow decent?
	beq +
	dex
	bne exit

+	jsr DoJump

exit:
	jmp $CCC2		;Bye-bye!