NES do'h

	.inesprg $01
	.ineschr $01
	.inesmap $00
	.inesmir $01

; variables
	.rsset $0000
gameState .rs 2

controller1 .rs 1
controller2 .rs 1

pLo .rs 1
pHi .rs 1

updatingBG .rs 1

ballXPos .rs 1
ballYPos .rs 1
ballXVel .rs 1
ballYVel .rs 1

paddle1Y .rs 1
paddle2Y .rs 1
; end variables

; constants
GSTITLE = $01
GSPLAYING = $02
GSGAMEOVER = $03

LEFTWALL = $20
RIGHTWALL = $DA
ROOF = $20
FLOOR = $C0

PADDLE1X = $2A
PADDLE2X = $D0
; end constants

	.bank $00
	.org $C000
; subroutines
VBlankWait:
	BIT $2002
	BPL VBlankWait
	RTS

SetBGPointer:
	TXA
	STA pLo
	TYA
	STA pHi
	RTS

LoadBG:
	LDA $2002
	LDA #$20
	STA $2006
	LDA #$00
	STA $2006
	LDX #$00
	LDY #$00
LoadBGLoop:
	LDA [pLo], Y
	STA $2007
	INY
	BNE LoadBGLoop
	INC pHi
	INX
	CPX #$04
	BNE LoadBGLoop
	RTS

ReadController1:
	LDA #$01
	STA $4016
	LDA #$00
	STA $4016
	LDX #$08
Controller1Loop:
	LDA $4016
	LSR A
	ROL controller1
	DEX
	BNE Controller1Loop
	RTS

ReadController2:
	LDA #$01
	STA $4016
	LDA #$00
	STA $4016
	LDX #$08
Controller2Loop:
	LDA $4017
	LSR A
	ROL controller2
	DEX
	BNE Controller2Loop
	RTS
; end subroutines

Reset:
	SEI
	CLD
	LDX #$40
	STX $4017
	LDX #$FF
	TXS
	INX
	STX $2000
	STX $2001
	STX $4010

	BIT $2002
	JSR VBlankWait

ClrMem:
	LDA #$00
	STA $0000, X
	STA $0100, X
	STA $0300, X
	STA $0400, X
	STA $0500, X
	STA $0600, X
	STA $0700, X
	LDA #$FE
	STA $0200, X
	INX
	BNE ClrMem

	JSR VBlankWait

	LDA $2002
	LDA #$3F
	STA $2006
	LDA #$00
	STA $2006
LoadPalettes:
	LDA Palettes, X
	STA $2007
	INX
	CPX #$20
	BNE LoadPalettes

; define some staring values
	LDA #GSTITLE
	STA gameState

	LDA #$00
	STA $2003

	LDA #%10010000
	STA $2000

Forever:
	LDA gameState
	CMP gameState+1
	BEQ GameStatesDone

	JSR ReadController1
	JSR ReadController2

GameStates:
	LDA gameState
	CMP #GSTITLE
	BEQ TitleScreen

	LDA gameState
	CMP #GSPLAYING
	BEQ PlayScreen

	LDA gameState
	CMP #GSGAMEOVER
	BEQ GameOverScreen
GameStatesDone:

	JMP Forever

Nmi:
	PHA
	TXA
	PHA
	TYA
	PHA

	LDA #$02
	STA $4014

	LDA updatingBG
	BNE DoNotDraw

	LDA #%00011110
	STA $2001

DoNotDraw:

	LDA #$00
	STA $2005
	STA $2005

	PLA
	TAY
	PLA
	TAX
	PLA

	RTI

TitleScreen:
	LDA #$00
	STA $2001

	LDA #$01
	STA updatingBG

	LDA gameState
	STA gameState+1

	LDX #LOW(TitleBG)
	LDY #HIGH(TitleBG)
	JSR SetBGPointer
	JSR LoadBG

	LDA #$00
	STA updatingBG

	LDA controller1
	AND #%00010000
	BEQ GameStatesDone

	LDA #GSPLAYING
	STA gameState
	JMP GameStatesDone

PlayScreen:
	LDA #$00
	STA $2000
	STA $2001
	JMP GameStatesDone

GameOverScreen:
	JMP GameStatesDone