Pong

  .inesprg 1   ; 1x 16KB PRG code
  .ineschr 1   ; 1x  8KB CHR data
  .inesmap 0   ; mapper 0 = NROM, no bank swapping
  .inesmir 1   ; background mirroring


;;;;;;;;;;;;;;;

;; DECLARE SOME VARIABLES HERE
  .rsset $0000  ;;start variables at ram location 0

gamestate  .rs 1  ; .rs 1 means reserve one byte of space
ballx      .rs 1  ; ball horizontal position
bally      .rs 1  ; ball vertical position
ballup     .rs 1  ; 1 = ball moving up
balldown   .rs 1  ; 1 = ball moving down
ballleft   .rs 1  ; 1 = ball moving left
ballright  .rs 1  ; 1 = ball moving right
ballspeedx .rs 1  ; ball horizontal speed per frame
ballspeedy .rs 1  ; ball vertical speed per frame
paddle1y      .rs 1  ; paddle vertical position
paddle2y      .rs 1  ; paddle vertical position
paddle1y2      .rs 1  ; paddle vertical position
paddle2y2      .rs 1  ; paddle vertical position
buttons1   .rs 1  ; player 1 gamepad buttons, one bit per button
buttons2   .rs 1  ; player 2 gamepad buttons, one bit per button
scoreOnes     .rs 1  ; byte for each digit in the decimal score
scoreTens     .rs 1
scoreHundreds .rs 1
scoreOnes2     .rs 1  ; byte for each digit in the decimal score
scoreTens2     .rs 1
scoreHundreds2 .rs 1


;; DECLARE SOME CONSTANTS HERE
STATETITLE     = $00  ; displaying title screen
STATEPLAYING   = $01  ; move paddles/ball, check for collisions
STATEGAMEOVER  = $02  ; displaying game over screen

RIGHTWALL      = $F4  ; when ball reaches one of these, do something
TOPWALL        = $20
BOTTOMWALL     = $E0
LEFTWALL       = $04

PADDLE1X       = $08  ; horizontal position for paddles, doesnt move
PADDLE2X       = $F0

PS1 = $01  ; paddle vertical speed per frame
PS2 = $01  ; paddle vertical speed per frame

;;;;;;;;;;;;;;;;;;




  .bank 0
  .org $C000
RESET:
  SEI          ; disable IRQs
  CLD          ; disable decimal mode
  LDX #$40
  STX $4017    ; disable APU frame IRQ
  LDX #$FF
  TXS          ; Set up stack
  INX          ; now X = 0
  STX $2000    ; disable NMI
  STX $2001    ; disable rendering
  STX $4010    ; disable DMC IRQs

vblankwait1:       ; First wait for vblank to make sure PPU is ready
  BIT $2002
  BPL vblankwait1

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

vblankwait2:      ; Second wait for vblank, PPU is ready after this
  BIT $2002
  BPL vblankwait2


LoadPalettes:
  LDA $2002             ; read PPU status to reset the high/low latch
  LDA #$3F
  STA $2006             ; write the high byte of $3F00 address
  LDA #$00
  STA $2006             ; write the low byte of $3F00 address
  LDX #$00              ; start out at 0
LoadPalettesLoop:
  LDA palette, x        ; load data from address (palette + the value in x)
                          ; 1st time through loop it will load palette+0
                          ; 2nd time through loop it will load palette+1
                          ; 3rd time through loop it will load palette+2
                          ; etc
  STA $2007             ; write to PPU
  INX                   ; X = X + 1
  CPX #$20              ; Compare X to hex $10, decimal 16 - copying 16 bytes = 4 sprites
  BNE LoadPalettesLoop  ; Branch to LoadPalettesLoop if compare was Not Equal to zero
                        ; if compare was equal to 32, keep going down





;;;Set some initial ball stats
  LDA #$01
  STA balldown
  STA ballright
  LDA #$00
  STA ballup
  STA ballleft

  LDA #$50
  STA bally

  LDA #$80
  STA ballx

  LDA #$06
  STA ballspeedx
  STA ballspeedy

  LDA #$50
  STA paddle1y
  STA paddle2y

  LDA #$58
  STA paddle1y2
  STA paddle2y2


  ;;;Set initial score value
  LDA #$00
  STA scoreOnes
  STA scoreTens
  STA scoreHundreds
  STA scoreOnes2
  STA scoreTens2
  STA scoreHundreds2

  ;;:Set starting game state
  LDA #STATETITLE
  STA gamestate



  LDA #%10010000   ; enable NMI, sprites from Pattern Table 0, background from Pattern Table 1
  STA $2000

  LDA #%00011110   ; enable sprites, enable background, no clipping on left side
  STA $2001

Forever:
  JMP Forever     ;jump back to Forever, infinite loop, waiting for NMI



NMI:
  LDA #$00
  STA $2003       ; set the low byte (00) of the RAM address
  LDA #$02
  STA $4014       ; set the high byte (02) of the RAM address, start the transfer

  JSR DrawScore
  JSR DrawScore2

  ;;This is the PPU clean up section, so rendering the next frame starts properly.
  LDA #%10010000   ; enable NMI, sprites from Pattern Table 0, background from Pattern Table 1
  STA $2000
  LDA #%00011110   ; enable sprites, enable background, no clipping on left side
  STA $2001
  LDA #$00        ;;tell the ppu there is no background scrolling
  STA $2005
  STA $2005

  ;;;all graphics updates done by here, run game engine


  JSR ReadController1  ;;get the current button data for player 1
  JSR ReadController2  ;;get the current button data for player 2


GameEngine:
  LDA gamestate
  CMP #STATETITLE
  BEQ EngineTitle    ;;game is displaying title screen

  LDA gamestate
  CMP #STATEGAMEOVER
  BEQ EngineGameOver  ;;game is displaying ending screen

  LDA gamestate
  CMP #STATEPLAYING
  BEQ EnginePlaying   ;;game is playing
GameEngineDone:

  JSR UpdateSprites  ;;set ball/paddle sprites from positions

  JSR MovePaddle1  ;;get the current button data for player 1
  JSR MovePaddle2  ;;get the current button data for player 2
  JSR CheckPaddleCollision

  RTI             ; return from interrupt




;;;;;;;;

EngineTitle:
        LDA buttons1
        AND #%00010000
        BEQ .return
        LDA #STATEPLAYING
        STA gamestate
        JMP EnginePlaying
.return
        JMP GameEngine

;;;;;;;;;

EngineGameOver:
        LDA buttons1
        AND #%00010000
        BEQ .return1
        LDA #STATEPLAYING
        STA gamestate
        LDA #$00
  STA scoreOnes
  STA scoreTens
  STA scoreHundreds
  STA scoreOnes2
  STA scoreTens2
  STA scoreHundreds2
        JMP EnginePlaying
.return1
        JMP GameEngine

;;;;;;;;;;;

EnginePlaying:

MoveBallRight:
  LDA ballright
  BEQ MoveBallRightDone   ;;if ballright=0, skip this section

  LDA ballx
  CLC
  ADC ballspeedx        ;;ballx position = ballx + ballspeedx
  STA ballx

  LDA ballx
  CMP #RIGHTWALL
  BCC MoveBallRightDone      ;;if ball x < right wall, still on screen, skip next section
  LDA #$00
  STA ballright
  LDA #$01
  STA ballleft         ;;bounce, ball now moving left
  ;;in real game, give point to player 1, reset ball
  jsr IncrementScore1
MoveBallRightDone:


MoveBallLeft:
  LDA ballleft
  BEQ MoveBallLeftDone   ;;if ballleft=0, skip this section

  LDA ballx
  SEC
  SBC ballspeedx        ;;ballx position = ballx - ballspeedx
  STA ballx

  LDA ballx
  CMP #LEFTWALL
  BCS MoveBallLeftDone      ;;if ball x > left wall, still on screen, skip next section
  LDA #$01
  STA ballright
  LDA #$00
  STA ballleft         ;;bounce, ball now moving right
  ;;in real game, give point to player 2, reset ball
    jsr IncrementScore2
MoveBallLeftDone:


MoveBallUp:
  LDA ballup
  BEQ MoveBallUpDone   ;;if ballup=0, skip this section

  LDA bally
  SEC
  SBC ballspeedy        ;;bally position = bally - ballspeedy
  STA bally

  LDA bally
  CMP #TOPWALL
  BCS MoveBallUpDone      ;;if ball y > top wall, still on screen, skip next section
  LDA #$01
  STA balldown
  LDA #$00
  STA ballup         ;;bounce, ball now moving down
MoveBallUpDone:


MoveBallDown:
  LDA balldown
  BEQ MoveBallDownDone   ;;if ballup=0, skip this section

  LDA bally
  CLC
  ADC ballspeedy        ;;bally position = bally + ballspeedy
  STA bally

  LDA bally
  CMP #BOTTOMWALL
  BCC MoveBallDownDone      ;;if ball y < bottom wall, still on screen, skip next section
  LDA #$00
  STA balldown
  LDA #$01
  STA ballup         ;;bounce, ball now moving down
MoveBallDownDone:
  JMP GameEngineDone

MovePaddle1:

    lda buttons1        ;load the current button state for controller1
    and #%00000100   ;isolate the bit representing "up", by clearing all the other bits
    beq ReadDownDone          ;if the result was 0, then the "up" bit was clear (thus not pressed), so skip the following code
    ;...

  LDA $0204 ; load sprite 2 position
  CLC ; make sure carry flag is set
  ADC #PS1 ; A = A - 1
  STA $0204 ; save sprite 2 position
  LDA $0204
  STA paddle1y
  LDA $020C ; load sprite 2 position
  CLC ; make sure carry flag is set
  ADC #PS1 ; A = A - 1
  STA $020C ; save sprite 2 position
  LDA $020C
  STA paddle1y2
  LDA paddle1y2
  CMP #BOTTOMWALL
  BCC ReadDownDone
  SEC  ; make sure carry flag is set
  SBC #$01 ; A = A - 1
  STA paddle1y2
  LDA paddle1y
  SEC  ; make sure carry flag is set
  SBC #$01 ; A = A - 1
  STA paddle1y

;  LDA paddle1y
;  SEC
;  SBC PS1        ;;bally position = bally - ballspeedy
;  STA paddle1y
;
;  LDA paddle1y
;  CMP #TOPWALL
;  BCS ReadDownDone      ;;if ball y > top wall, still on screen, skip next section
;  LDA #$01
;  STA paddle1down
;  LDA #$00
;  STA paddle1down         ;;bounce, ball now moving down

ReadDownDone:

    lda buttons1        ;load the current button state for controller1
    and #%00001000   ;isolate the bit representing "up", by clearing all the other bits
    beq ReadUpDone           ;if the result was 0, then the "up" bit was clear (thus not pressed), so skip the following code
    ;...

;  LDA $4016
;  CMP #%00001000
;  BNE ReadUpDone
  LDA $0204 ; load sprite 2 position
  SEC ; make sure carry flag is set
  SBC #PS1 ; A = A - 1
  STA $0204 ; save sprite 2 position
  LDA $0204
  STA paddle1y
  LDA $020C ; load sprite 2 position
  SEC ; make sure carry flag is set
  SBC #PS1 ; A = A - 1
  STA $020C ; save sprite 2 position
  LDA $020C
  STA paddle1y2
  LDA paddle1y
  CMP #TOPWALL
  BCS ReadUpDone
  CLC ; make sure carry flag is set
  ADC #$01 ; A = A - 1
  STA paddle1y
  LDA paddle1y2
  CLC ; make sure carry flag is set
  ADC #$01 ; A = A - 1
  STA paddle1y2
;  LDA paddle1y
;  SEC
;  SBC PS1        ;;bally position = bally - ballspeedy
;  STA paddle1y
;
;  LDA paddle1y
;  CMP #TOPWALL
;  BCS ReadUpDone      ;;if ball y > top wall, still on screen, skip next section
;  LDA #$01
;  STA paddle1down
;  LDA #$00
;  STA paddle1up         ;;bounce, ball now moving down
ReadUpDone:
  RTS

MovePaddle2:

    lda buttons2        ;load the current button state for controller1
    and #%00000100   ;isolate the bit representing "up", by clearing all the other bits
    beq MovePaddleDownDone           ;if the result was 0, then the "up" bit was clear (thus not pressed), so skip the following code
    ;...
  LDA $0208 ; load sprite 2 position
  CLC ; make sure carry flag is set
  ADC #PS2 ; A = A - 1
  STA $0208 ; save sprite 2 position
  LDA $0208
  STA paddle2y
  LDA $0210 ; load sprite 2 position
  CLC ; make sure carry flag is set
  ADC #PS2 ; A = A - 1
  STA $0210 ; save sprite 2 position
  LDA $0210
  STA paddle2y2
  LDA paddle2y2
  CMP #BOTTOMWALL
  BCC MovePaddleDownDone
  SEC  ; make sure carry flag is set
  SBC #$01 ; A = A - 1
  STA paddle2y2
  LDA paddle2y
  SEC  ; make sure carry flag is set
  SBC #$01 ; A = A - 1
  STA paddle2y

MovePaddleDownDone:

    lda buttons2        ;load the current button state for controller1
    and #%00001000   ;isolate the bit representing "up", by clearing all the other bits
    beq MovePaddleUpDone           ;if the result was 0, then the "up" bit was clear (thus not pressed), so skip the following code
    ;...
  LDA $0208 ; load sprite 2 position
  SEC ; make sure carry flag is set
  SBC #PS2 ; A = A - 1
  STA $0208 ; save sprite 2 position
  LDA $0208
  STA paddle2y
  LDA $0210 ; load sprite 2 position
  SEC ; make sure carry flag is set
  SBC #PS2 ; A = A - 1
  STA $0210 ; save sprite 2 position
  LDA $0210
  STA paddle2y2
  LDA paddle2y
  CMP #TOPWALL
  BCS MovePaddleUpDone
  CLC ; make sure carry flag is set
  ADC #$01 ; A = A - 1
  STA paddle2y
  LDA paddle2y2
  CLC ; make sure carry flag is set
  ADC #$01 ; A = A - 1
  STA paddle2y2

  ;;if up button pressed
  ;;  if paddle top > top wall
  ;;    move paddle top and bottom up
MovePaddleUpDone:
  RTS



Skip:

CheckPaddleCollision:
  LDA ballx
  CMP #PADDLE1X+8
  BCS CheckPaddleCollisionDone      ;;if ball x > left wall, still on screen, skip next section
  LDA bally
  CMP paddle1y
  BCS CheckPaddleCollisionDone      ;;if ball y > top wall, still on screen, skip next section
  LDA bally
  CMP paddle1y2
  BCC CheckPaddleCollisionDone      ;;if ball y < bottom wall, still on screen, skip next section
;  LDA ballx
;  CLC
;  ADC ballspeedx        ;;ballx position = ballx - ballspeedx
;  STA ballx
  LDA #$01
  STA ballright
  LDA #$00
  STA ballleft         ;;bounce, ball now moving right
  LDA bally
  CMP paddle1y2
  BCS .point2
  LDA #$01
  STA ballup
  LDA #$00
  STA balldown
;  LDA bally
;  SEC
;  SBC ballspeedy        ;;bally position = bally - ballspeedy
;  STA bally
  JMP CheckPaddleCollisionDone
.point2
;  LDA #$01
;  LDA bally
;  CLC
;  ADC ballspeedy        ;;bally position = bally - ballspeedy
;  STA bally
  LDA #$01
  STA balldown
  LDA #$00
  STA ballup

;  LDA #$00
;  STA ballleft
;  LDA #$00
;  STA balldown
;  LDA #$00
;  STA ballup
CheckPaddleCollisionDone:
  RTS
;  JMP GameEngineDone




UpdateSprites:
  LDA bally  ;;update all ball sprite info
  STA $0200

  LDA #$30
  STA $0201

  LDA #$00
  STA $0202

  LDA ballx
  STA $0203

  LDA paddle1y  ;;update all ball sprite info
  STA $0204

  LDA #$7F
  STA $0205

  LDA #$10
  STA $0206

  LDA #PADDLE1X
  STA $0207

  LDA paddle1y2  ;;update all ball sprite info
  STA $020C

  LDA #$7F
  STA $020D

  LDA #$10
  STA $020E

  LDA #PADDLE1X
  STA $020F

  LDA paddle2y
  STA $0208

  LDA #$7F
  STA $0209

  LDA #$10
  STA $020A

  LDA #PADDLE2X
  STA $020B

  LDA paddle2y2
  STA $0210

  LDA #$7F
  STA $0211

  LDA #$10
  STA $0212

  LDA #PADDLE2X
  STA $0213

  ;;update paddle sprites
  RTS


DrawScore:
  LDA $2002
  LDA #$20
  STA $2006
  LDA #$20
  STA $2006          ; start drawing the score at PPU $2020

.Zero1
  LDA scoreHundreds      ; last digit
  cmp #$00
  beq .pointa
  cmp #$24
  bne .point
  LDA scoreTens      ; next digit
  cmp #$00
  bne .point
  LDA #$24
  STA scoreTens
  JMP .point
.pointa
  LDA #$24
  STA scoreHundreds

.point
  LDA scoreHundreds  ; get first digit
;  CLC
;  ADC #$30           ; add ascii offset  (this is UNUSED because the tiles for digits start at 0)
  STA $2007          ; draw to background
  LDA scoreTens      ; next digit
;  CLC
;  ADC #$30           ; add ascii offset
  STA $2007
  LDA scoreOnes      ; last digit
;  CLC
;  ADC #$30           ; add ascii offset
  STA $2007
  RTS

DrawScore2:
  LDA $2002
  LDA #$20
  STA $2006
  LDA #$3C
  STA $2006          ; start drawing the score at PPU $203C

.Zero
  LDA scoreHundreds2      ; last digit
  cmp #$00
  beq .point2b
  cmp #$24
  bne .point2
  LDA scoreTens2      ; next digit
  cmp #$00
  bne .point2
  LDA #$24
  STA scoreTens2
  JMP .point2
.point2b
  LDA #$24
  STA scoreHundreds2

.point2
  LDA scoreHundreds2  ; get first digit
;  CLC
;  ADC #$30           ; add ascii offset  (this is UNUSED because the tiles for digits start at 0)
  STA $2007          ; draw to background
  LDA scoreTens2      ; next digit
;  CLC
;  ADC #$30           ; add ascii offset
  STA $2007
  LDA scoreOnes2      ; last digit
;  CLC
;  ADC #$30           ; add ascii offset
  STA $2007
  RTS


IncrementScore1:
IncOnes:
  LDA scoreOnes      ; load the lowest digit of the number
  CLC
  ADC #$01           ; add one
  STA scoreOnes
  CMP #$0A           ; check if it overflowed, now equals 10
  bne IncDone        ; if there was no overflow, all done
IncTens:
  LDA #$00
  STA scoreOnes      ; wrap digit to 0
  LDA scoreTens      ; load the next digit
  cmp #$24
  bne .add
  sec
  sbc #$24
  STA scoreTens
.add
  LDA scoreTens      ; load the next digit
  CLC
  ADC #$01           ; add one, the carry from previous digit
  STA scoreTens
  CMP #$0A           ; check if it overflowed, now equals 10
  bne IncDone        ; if there was no overflow, all done
IncHundreds:
  LDA #$00
  STA scoreTens      ; wrap digit to 0
  LDA scoreHundreds  ; load the next digit
  cmp #$24
  bne .add1
  sec
  sbc #$24
  STA scoreHundreds
.add1
  LDA scoreHundreds  ; load the next digit
  CLC
  ADC #$01           ; add one, the carry from previous digit
  STA scoreHundreds
IncDone:
  JMP IncDone2

IncrementScore2:
IncOnes2:
  LDA scoreOnes2      ; load the lowest digit of the number
  CLC
  ADC #$01           ; add one
  STA scoreOnes2
  CMP #$0A           ; check if it overflowed, now equals 10
  BNE IncDone2        ; if there was no overflow, all done
IncTens2:
  LDA #$00
  STA scoreOnes2      ; wrap digit to 0
  LDA scoreTens2      ; load the next digit
  cmp #$24
  bne .add
  sec
  sbc #$24
  STA scoreTens2
.add
  LDA scoreTens2      ; load the next digit
  CLC
  ADC #$01           ; add one, the carry from previous digit
  STA scoreTens2
  CMP #$0A           ; check if it overflowed, now equals 10
  BNE IncDone2        ; if there was no overflow, all done
IncHundreds2:
  LDA #$00
  STA scoreTens2      ; wrap digit to 0
  LDA scoreHundreds2  ; load the next digit
  cmp #$24
  bne .add1
  sec
  sbc #$24
  STA scoreHundreds2
.add1
  LDA scoreHundreds2  ; load the next digit
  CLC
  ADC #$01           ; add one, the carry from previous digit
  STA scoreHundreds2
IncDone2:
  LDA scoreHundreds
  cmp #$01
  BEQ GameOver
  LDA scoreHundreds2
  cmp #$01
  BEQ GameOver

ReadController1:
  LDA #$01
  STA $4016
  LDA #$00
  STA $4016
  LDX #$08
ReadController1Loop:
  LDA $4016
  LSR A            ; bit0 -> Carry
  ROL buttons1     ; bit0 <- Carry
  DEX
  BNE ReadController1Loop
  RTS

ReadController2:
  LDA #$01
  STA $4016
  LDA #$00
  STA $4016
  LDX #$08
ReadController2Loop:
  LDA $4017
  LSR A            ; bit0 -> Carry
  ROL buttons2     ; bit0 <- Carry
  DEX
  BNE ReadController2Loop
  RTS

GameOver:
        LDA #STATEGAMEOVER
        STA gamestate
        JMP GameEngine



;;;;;;;;;;;;;;



  .bank 1
  .org $E000
palette:
  .db $22,$29,$1A,$0F,  $22,$36,$17,$0F,  $22,$30,$21,$0F,  $22,$27,$17,$0F   ;;background palette
  .db $22,$1C,$15,$14,  $22,$02,$38,$3C,  $22,$1C,$15,$14,  $22,$02,$38,$3C   ;;sprite palette

sprites:
     ;vert tile attr horiz
        .db $52, $01, $00, $28 ; Player1 paddle top
        .db $5A, $11, $00, $28 ; Player1 paddle bottom

        .db $52, $01, $01, $D8 ; Player2 paddle top
        .db $5A, $11, $01, $D8 ; Player2 paddle bottom

        .db $74, $02, $02, $78 ; Ball



  .org $FFFA     ;first of the three vectors starts here
  .dw NMI        ;when an NMI happens (once per frame if enabled) the
                   ;processor will jump to the label NMI:
  .dw RESET      ;when the processor first turns on or is reset, it will jump
                   ;to the label RESET:
  .dw 0          ;external interrupt IRQ is not used in this tutorial


;;;;;;;;;;;;;;


  .bank 2
  .org $0000
  .incbin "mario.chr"   ;includes 8KB graphics file from SMB1