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sprite display not as expected

Started by yllawwally, Feb 3 2010 3:32 PM

7 replies to this topic

#1 yllawwally  

    Star Raider

  • 56 posts
    • Joined: 15-May 09
  • Location:Corvallis, OR

Posted Wed Feb 3, 2010 3:32 PM

I'm trying to learn 2600 programming. I took the face example from one of the tutorials here. I modified it to have alternate pics of the player every 8 screens. So that I could do a walking animation. However the top line seems to be a copy of the bottom line. I can't see what I'm doing wrong. I was hoping someone could help me find my error.

; move a happy face with the joystick by Kirk Israel
; (with a can't'dodge'em line sweeping across the screen)

	processor 6502
	include vcs.h
	org $F000

YPosFromBot = $80;
VisiblePlayerLine = $81;
PICS = $93;
PICSNUM = $94;

;generic start up stuff...
Start
	SEI	
	CLD  	
	LDX #$FF	
	TXS	
	LDA #0	
	STA PICSNUM
	
ClearMem 
	STA 0,X		
	DEX		
	BNE ClearMem	
	
	LDA #$00   ;start with a black background
	STA COLUBK	
	LDA #$1C   ;lets go for bright yellow, the traditional color for happyfaces
	STA COLUP0
;Setting some variables...
	LDA #80
	STA YPosFromBot	;Initial Y Position



;; Let's set up the sweeping line. as Missile 1

	
	LDA #2
	STA ENAM1  ;enable it
	LDA #33
	STA COLUP1 ;color it

	LDA #$20	
	STA NUSIZ1	;make it quadwidth (not so thin, that)

	
	LDA #$F0	; -1 in the left nibble
	STA HMM1	; of HMM1 sets it to moving


;VSYNC time
MainLoop
	LDA #2
	STA VSYNC	
	STA WSYNC	
	STA WSYNC 	
	STA WSYNC	
	LDA #43	
	STA TIM64T	
	LDA #0
	STA VSYNC 	


;Main Computations; check down, up, left, right
;general idea is to do a BIT compare to see if 
;a certain direction is pressed, and skip the value
;change if so

;
;Not the most effecient code, but gets the job done,
;including diagonal movement
;

; for up and down, we INC or DEC
; the Y Position

	LDA #010000	;Down?
	BIT SWCHA 
	BNE SkipMoveDown
	INC YPosFromBot
SkipMoveDown

	LDA #100000	;Up?
	BIT SWCHA 
	BNE SkipMoveUp
	DEC YPosFromBot
SkipMoveUp

; for left and right, we're gonna 
; set the horizontal speed, and then do
; a single HMOVE.  We'll use X to hold the
; horizontal speed, then store it in the 
; appropriate register




;assum horiz speed will be zero
	LDX #0	


	LDA #%01000000	;Left?
	BIT SWCHA 
	BNE SkipMoveLeft
	LDX #$10	;a 1 in the left nibble means go left


;; moving left, so we need the mirror image
	LDA #001000   ;a 1 in D3 of REFP0 says make it mirror
	STA REFP0

SkipMoveLeft

	LDA #%10000000	;Right?
	BIT SWCHA 
	BNE SkipMoveRight
	LDX #$F0	;a -1 in the left nibble means go right...

;; moving right, cancel any mirrorimage
	LDA #000000
	STA REFP0

SkipMoveRight


	STX HMP0	;set the move for player 0, not the missile like last time...



; see if player and missile collide, and change the background color if so

	;just a review...comparisons of numbers always seem a little backwards to me,
	;since it's easier to load up the accumulator with the test value, and then
	;compare that value to what's in the register we're interested.
	;in this case, we want to see if D7 of CXM1P (meaning Player 0 hit
	; missile 1) is on. So we put 10000000 into the Accumulator,
	;then use BIT to compare it to the value in CXM1P

	LDA #%10000000
	BIT CXM1P		
	BEQ NoCollision	;skip if not hitting...
	LDA YPosFromBot	;must be a hit! load in the YPos...
	STA COLUBK	;and store as the bgcolor
NoCollision
	STA CXCLR	;reset the collision detection for next time

	INC  PICSNUM

	LDA PICSNUM
	AND #15		;every 8th screen swap to next image of player
	CMP #8
	BEQ PICSET4
	JMP PICSET3
PICSET4	LDA  PICS
	CMP  #8
	BEQ PICSET
	LDA  #8
	JMP PICSET2
PICSET	LDA  #0
PICSET2	STA PICS
PICSET3

WaitForVblankEnd
	LDA INTIM	
	BNE WaitForVblankEnd	
	LDY #191 	


	STA WSYNC	
	STA HMOVE 	
	
	STA VBLANK  	


;main scanline loop...



PreScanLoop
;set player graphic to all zeros for this line, and then see if 
;we need to load it with graphic data
	LDA #0		
	STA GRP0  

ScanLoop 
	STA WSYNC 	

; here the idea is that VisiblePlayerLine
; is zero if the line isn't being drawn now,
; otherwise it's however many lines we have to go

CheckActivatePlayer
	CPY YPosFromBot
	BNE SkipActivatePlayer
	LDA #8
	STA VisiblePlayerLine 
SkipActivatePlayer





;set player graphic to all zeros for this line, and then see if 
;we need to load it with graphic data
	LDA #0		
	STA GRP0  

;
;if the VisiblePlayerLine is non zero,
;we're drawing it now!
;
	LDX VisiblePlayerLine	;check the visible player line...
	BEQ FinishPlayer		;skip the drawing if its zero...
IsPlayerOn	
	


	TXA		;Transfers the byte in the X Register to the Accumulator
	ADC PICS	;add value of pics to Accumulator
	TAX		;Transfers the byte in the Accumulator to the X Register
	LDA BigHeadGraphic-1,X	;shift to change which pic were showing
	
	


;	ORA #1		;creates a shield

	STA GRP0		;put that line as player graphic
	DEC VisiblePlayerLine 	;and decrement the line count
FinishPlayer




	DEY		

	BNE ScanLoop	


	LDA #2	

	STA WSYNC  	
	STA VBLANK 	
	LDX #24		



OverScanWait
	STA WSYNC
	DEX
	BNE OverScanWait
	JMP  MainLoop      


; here's the actual graphic! If you squint you can see its
; upsidedown smiling self
BigHeadGraphic
	.byte #010100
	.byte #010100
	.byte #011000
	.byte #011000
	.byte #%01111110
	.byte #010000
	.byte #011000
	.byte #011000


	.byte #010010
	.byte #010100
	.byte #011000
	.byte #011000
	.byte #%01111110
	.byte #010000
	.byte #011000
	.byte #011000

	.byte #010100
	.byte #010100
	.byte #011000
	.byte #011000
	.byte #%01111110
	.byte #010000
	.byte #011000
	.byte #011000


	.byte #010010
	.byte #010100
	.byte #011000
	.byte #011000
	.byte #%01111110
	.byte #010000
	.byte #011000
	.byte #011000

	org $FFFC
	.word Start
	.word Start

#2 e1will  

    Moonsweeper

  • 338 posts
    • Joined: 24-April 09

Posted Wed Feb 3, 2010 9:03 PM

You're setting the "first" GRP0 line AFTER you turn the screen on, so whatever was in GRP0 from the last pass gets drawn at the top.

If you put the "LDA #0" and "STA GRP0" lines BEFORE the STA WSYNC/STA HMOVE/STA VBLANK group, that should clear it out.

Hope this helps.

--Will

#3 yllawwally  

    Star Raider

  • 56 posts
    • Joined: 15-May 09
  • Location:Corvallis, OR

Posted Fri Feb 5, 2010 10:38 AM

Sorry I mischaracterized the issue. Really the problem was the first line of the player was a copy of the previous last line. However that wasn't what was happening. I used ADC to add a counter for each step. I didn't realize that if the carry flag was set an additional 1 would be added. So I placed a CLC before adc, which has fixed it.

#4 yllawwally  

    Star Raider

  • 56 posts
    • Joined: 15-May 09
  • Location:Corvallis, OR

Posted Thu Feb 11, 2010 3:29 PM

I seem to now have a problem using too many cycles. When the player and enemy are on the same lines, they get twice as tall. It seems that I should have cycles to spare. What am I doing wrong?


	processor 6502
	include vcs.h
	org $F000

;Variables ------

YPosFromBot = $80;
VisiblePlayerLine = $81;
PICS = $82;
ROLLING_COUNTER = $83;
Graphics_Buffer = $84
YPosFromBotE1 = $85;
VisibleEnemyLine = $86;
VisibleEnemyLineCurrent = $87;
EnemyLineBuffer = $88;
VisiblePlayerLineCurrent = $90;



; Constants ------
playerheight      ds #8;
enemyheight       ds #8;



;generic start up stuff...
Start
	SEI	
	CLD  	
	LDX #$FF	
	TXS	
	LDA #0	
	STA ROLLING_COUNTER
	STA PICS
	STA EnemyLineBuffer
	
ClearMem 
	STA 0,X		
	DEX		
	BNE ClearMem	
	
	LDA #$00   ;start with a black background
	STA COLUBK	
	LDA #$1C   ;lets go for bright yellow, the traditional color for happyfaces
	STA COLUP0
;Setting some variables...
	LDA #80
	STA YPosFromBot	;Initial Y Position
	STA YPosFromBotE1



;; Let's set up the sweeping line. as Missile 1

	
	LDA #2
	STA ENAM1  ;enable it
	LDA #33
	STA COLUP1 ;color it

	LDA #$10	
	STA NUSIZ1	;make it quadwidth (not so thin, that)

	LDA #000000	; set to not move
	STA HMM1	; of HMM1 sets it to moving



;VSYNC time
MainLoop
	LDA #2
	STA VSYNC	
	STA WSYNC	


; for up and down, we INC or DEC
; the Y Position

	LDA #010000	;Down?
	BIT SWCHA 
	BNE SkipMoveDown
	INC YPosFromBot
	INC YPosFromBotE1
	INC YPosFromBotE1
SkipMoveDown

	LDA #100000	;Up?
	BIT SWCHA 
	BNE SkipMoveUp
	DEC YPosFromBot
	DEC YPosFromBotE1
	DEC YPosFromBotE1
SkipMoveUp

; for left and right, we're gonna 
; set the horizontal speed, and then do
; a single HMOVE.  We'll use X to hold the
; horizontal speed, then store it in the 
; appropriate register




;assum horiz speed will be zero
	LDX #0	


	LDA #%01000000	;Left?
	BIT SWCHA 
	BNE SkipMoveLeft
	LDX #$10	;a 1 in the left nibble means go left


;; moving left, so we need the mirror image
	LDA #001000   ;a 1 in D3 of REFP0 says make it mirror
	STA REFP0

SkipMoveLeft

	LDA #%10000000	;Right?
	BIT SWCHA 
	BNE SkipMoveRight
	LDX #$F0	;a -1 in the left nibble means go right...

;; moving right, cancel any mirrorimage
	LDA #000000
	STA REFP0

SkipMoveRight


	STX HMP0	;set the move for player 0, not the missile like last time...



; see if player and missile collide, and change the background color if so

	;just a review...comparisons of numbers always seem a little backwards to me,
	;since it's easier to load up the accumulator with the test value, and then
	;compare that value to what's in the register we're interested.
	;in this case, we want to see if D7 of CXM1P (meaning Player 0 hit
	; missile 1) is on. So we put 10000000 into the Accumulator,
	;then use BIT to compare it to the value in CXM1P

	LDA #%10000000
	BIT CXM1P		
	BEQ NoCollision	;skip if not hitting...
	LDA YPosFromBot	;must be a hit! load in the YPos...
	STA COLUBK	;and store as the bgcolor
NoCollision
	STA CXCLR	;reset the collision detection for next time



	STA WSYNC ;//////////////////////////////////////////////

;setup pic animations ----------------------------------------------
	INC ROLLING_COUNTER

	LDA ROLLING_COUNTER
	AND #15		;every 8th screen swap to next image of player
	CMP #8
	BEQ PICSET4
	JMP PICSET3
PICSET4	LDA  PICS
	CMP  #8
	BEQ PICSET
	LDA  #8
	JMP PICSET2
PICSET	LDA  #0
PICSET2	STA PICS
PICSET3


	LDA ROLLING_COUNTER
	AND #25		;how often to move enemy, larger number is slower
	CMP #8
	BEQ PICSET5
	LDA #001111	; +1 in the left nibble
	JMP PICSET6
PICSET5	LDA #011111	; 0 in the left nibble
PICSET6	STA HMP1	; of HMP1 sets it to moving the enemy

	

	LDA #8
	CLC
	ADC PICS	;add value of pics to Accumulator 
	STA VisibleEnemyLineCurrent	
	
	LDA #8
	CLC
	ADC PICS	;add value of pics to Accumulator 
	STA VisiblePlayerLineCurrent

;setup pic animations ----------------------------------------------
	
	STA WSYNC ;//////////////////////////////////////////////	
	LDA #43	
	STA TIM64T	
	LDA #0
	STA VSYNC 	

;-------------------------
;-------------------------



WaitForVblankEnd
	LDA INTIM	
	BNE WaitForVblankEnd	
	LDY #191 	


	STA WSYNC	
	STA HMOVE 	
	
	STA VBLANK  	


;main scanline loop...



PreScanLoop

	LDA #0

ScanLoop ;start of kernal +++++++++++++++++++++++

	STA GRP0	;put that line as player graphic 0	 ;2 cycles
AFTERPLAYERDRAW


	LDA EnemyLineBuffer						 ;2 cycles
	STA GRP1	; put player 1 into grp1 2 cycles
AfterEnemyDraw

	DEY		;count down number of scan lines	  1 cycles

	LDA #8			;2 cycles

CheckActivatePlayer
	CPY YPosFromBot		;2 cycles
	BNE SkipActivatePlayer	;2 cycles
	STA VisiblePlayerLine 	;2 cycles
SkipActivatePlayer

CheckActivateEnemy
	CPY YPosFromBotE1	;2 cycles
	BNE SkipActivateEnemy	;2 cycles
	STA VisibleEnemyLine 	;2 cycles
SkipActivateEnemy




	LDA #0						 	;2 cycles
	STA EnemyLineBuffer					 ;2 cycles

	LDA VisibleEnemyLine	;check the visible enemy line... 2 cycles
	BEQ FinishEnemy		;skip the drawing if its zero... 2 cycles
IsEnemyOn	
	LDX VisibleEnemyLineCurrent		;2 cycles
	LDA EnemyGraphics-1,x			;2 cycles
	STA EnemyLineBuffer
	DEC VisibleEnemyLine			;2 cycles
	DEC VisibleEnemyLineCurrent		;2 cycles
FinishEnemy

	LDA VisiblePlayerLine	;check the visible player line... 2 cycles
	BEQ FinishPlayer	;skip the drawing if its zero...  2 cycles
IsPlayerOn	
	LDX VisiblePlayerLineCurrent				 ;2 cycles
	LDA MainPlayerGraphics-1,x	;shift to change which pic were showing 2 cycles
;	ORA #1		;creates a shield
	DEC VisiblePlayerLineCurrent				 ;2 cycles
	DEC VisiblePlayerLine					 ;2 cycles
FinishPlayer


	CPY #0						         ;2 cycles

	STA WSYNC 						 ;2 cycles
	BNE ScanLoop		 				 ;2 cycles
EndScanLoop ;end of kernal +++++++++++++++++

	STA WSYNC  	
	STA VBLANK 	
	LDX #24		



OverScanWait
	STA WSYNC
	DEX
	BNE OverScanWait
	JMP  MainLoop      



MainPlayerGraphics
	.byte #010100
	.byte #010100
	.byte #011000
	.byte #011000
	.byte #%01111110
	.byte #010000
	.byte #111000
	.byte #111000


	.byte #010010
	.byte #010100
	.byte #011000
	.byte #011000
	.byte #%01111110
	.byte #010000
	.byte #111000
	.byte #111000

EnemyGraphics
	.byte #%01111000
	.byte #%10000100
	.byte #001000
	.byte #010000
	.byte #010000
	.byte #010000
	.byte #111000
	.byte #111000


	.byte #%01111000
	.byte #%01001000
	.byte #010000
	.byte #100000
	.byte #100000
	.byte #100000
	.byte #%01110000
	.byte #%01110000

	org $FFFC
	.word Start
	.word Start

#5 Nukey Shay  

    Sheik Yerbouti

  • 20,365 posts
    • Joined: 24-June 01
  • Location:The land of Gorch

Posted Thu Feb 11, 2010 5:29 PM

You are using too many cycles...and you seem to be confused regarding how many cycles are taken by the various instructions / addressing modes. There are NO instructions that only take a single cycle (DEY above should be 2 cycles). Most of the LDAs and STA's above are 3 cycles (not 2). The DEC's are 5 cycles (again, not 2). Branches are 2 cycles if not taken, but 3 cycles if they are.

Worst-case scenario...which is when the program takes the long path (i.e. no branches taken to skip ahead)...is 84 cycles.

Edited by Nukey Shay, Thu Feb 11, 2010 5:45 PM.

#6 Nukey Shay  

    Sheik Yerbouti

  • 20,365 posts
    • Joined: 24-June 01
  • Location:The land of Gorch

Posted Thu Feb 11, 2010 6:24 PM

Correction...89 cycles worst-case in the scanline loop :P

#7 yllawwally  

    Star Raider

  • 56 posts
    • Joined: 15-May 09
  • Location:Corvallis, OR

Posted Thu Feb 11, 2010 6:44 PM

Thank you very much. I was using number of bytes as the cycle time. Which is why I was totally confused.

#8 yllawwally  

    Star Raider

  • 56 posts
    • Joined: 15-May 09
  • Location:Corvallis, OR

Posted Thu Mar 18, 2010 5:53 PM

I'm trying to convert this code to use skipdraw. However so far the graphics aren't correct. What am I doing wrong?

; move a happy face with the joystick by Kirk Israel
; (with a can't'dodge'em line sweeping across the screen)

	processor 6502
	include vcs.h
	org $F000

;Variables ------

YPosFromBot = $80;
VisiblePlayerLine = $81;
PICS = $82;
ROLLING_COUNTER = $83;
Graphics_Buffer = $84
YPosFromBotE1 = $85;
VisibleEnemyLine = $86;
VisibleEnemyLineCurrent = $87;
EnemyLineBuffer = $88;
VisiblePlayerLineCurrent = $90;
BG_0 = $91;
BG_1 = $92;
BG_2 = $93;



; Constants ------
playerheight      ds #8;


;generic start up stuff...
Start
	SEI	
	CLD  	
	LDX #$FF	
	TXS	
	LDA #0	
	STA ROLLING_COUNTER
	STA PICS
	STA EnemyLineBuffer
	
ClearMem 
	STA 0,X		
	DEX		
	BNE ClearMem	
	
	LDA #$00   ;start with a black background
	STA COLUBK	
	LDA #$1C   ;lets go for bright yellow, the traditional color for happyfaces
	STA COLUP0
;Setting some variables...
	LDA #80
	STA YPosFromBot	;Initial Y Position
	STA YPosFromBotE1

	LDA #010001		; 2 cycles
	STA BG_0		; 3 cycles
	STA BG_1		; 3 cycles
	STA BG_2		; 3 cycles

;; Let's set up the sweeping line. as Missile 1

	
	LDA #2
;	STA ENAM1  ;enable it
	LDA #33
	STA COLUP0 ;color it
	STA COLUP1 ;color it

	LDA #$10
;	STA NUSIZ0	;make it quadwidth (not so thin, that)
	STA NUSIZ1	;make it quadwidth (not so thin, that)

	LDA #000000	; set to not move
	STA HMM1	; of HMM1 sets it to moving



;VSYNC time
MainLoop ;+++++++++++++++++++++++++++The start of a new screen
	LDA #0
	STA GRP0
	STA GRP1	
	STA PF0
	STA PF1
	STA PF2
	LDA #2
	STA VSYNC	
	STA WSYNC	


; for up and down, we INC or DEC
; the Y Position

	LDA #010000	;Down?
	BIT SWCHA 
	BNE SkipMoveDown
	INC YPosFromBot
	INC YPosFromBotE1
	INC YPosFromBotE1
SkipMoveDown

	LDA #100000	;Up?
	BIT SWCHA 
	BNE SkipMoveUp
	DEC YPosFromBot
	DEC YPosFromBotE1
	DEC YPosFromBotE1
SkipMoveUp

; for left and right, we're gonna 
; set the horizontal speed, and then do
; a single HMOVE.  We'll use X to hold the
; horizontal speed, then store it in the 
; appropriate register




;assum horiz speed will be zero
	LDX #0	


	LDA #%01000000	;Left?
	BIT SWCHA 
	BNE SkipMoveLeft
	LDX #$10	;a 1 in the left nibble means go left


;; moving left, so we need the mirror image
	LDA #001000   ;a 1 in D3 of REFP0 says make it mirror
	STA REFP0
	STA REFP1
SkipMoveLeft

	LDA #%10000000	;Right?
	BIT SWCHA 
	BNE SkipMoveRight
	LDX #$F0	;a -1 in the left nibble means go right...

;; moving right, cancel any mirrorimage
	LDA #000000
	STA REFP0
	STA REFP1

SkipMoveRight

	
	STX HMP0	;set the move for player 0, not the missile like last time...
	STX HMP1	;set the move for player 0, not the missile like last time...



; see if player and missile collide, and change the background color if so

	;just a review...comparisons of numbers always seem a little backwards to me,
	;since it's easier to load up the accumulator with the test value, and then
	;compare that value to what's in the register we're interested.
	;in this case, we want to see if D7 of CXM1P (meaning Player 0 hit
	; missile 1) is on. So we put 10000000 into the Accumulator,
	;then use BIT to compare it to the value in CXM1P

	LDA #%10000000
	BIT CXM1P		
	BEQ NoCollision	;skip if not hitting...
	LDA YPosFromBot	;must be a hit! load in the YPos...
	STA COLUBK	;and store as the bgcolor
NoCollision
	STA CXCLR	;reset the collision detection for next time

	STA WSYNC ;//////////////////////////////////////////////

;setup pic animations ----------------------------------------------
	INC ROLLING_COUNTER

	LDA ROLLING_COUNTER
	AND #15		;every 8th screen swap to next image of player
	CMP #8
	BEQ PICSET4
	JMP PICSET3
PICSET4	LDA  PICS
	CMP  #8
	BEQ PICSET
	LDA  #8
	JMP PICSET2
PICSET	LDA  #0
PICSET2	STA PICS
PICSET3


	LDA ROLLING_COUNTER
	AND #25		;how often to move enemy, larger number is slower
	CMP #8
	BEQ PICSET5
	LDA #001111	; +1 in the left nibble
	JMP PICSET6
PICSET5	LDA #011111	; 0 in the left nibble
PICSET6	STA HMP1	; of HMP1 sets it to moving the enemy

	

	LDA #8
	CLC
	ADC PICS	;add value of pics to Accumulator 
	STA VisibleEnemyLineCurrent	
	
	LDA #8
	CLC
	ADC PICS	;add value of pics to Accumulator 
	STA VisiblePlayerLineCurrent

;setup pic animations ----------------------------------------------
	
	STA WSYNC ;//////////////////////////////////////////////	
	LDA #43	
	STA TIM64T	
	LDA #0
	STA VSYNC 	

;------------------------- setup backgrounds 20 pixels accross
	LDA #255			; 3 cycles
	STA PF0			; 3 cycles
	STA PF1			; 3 cycles
	STA PF2			; 3 cycles
;-------------------------



WaitForVblankEnd
	LDA INTIM	
	BNE WaitForVblankEnd	
	LDY #4 ; was 191 	


	STA WSYNC	
	STA HMOVE 	
	
	STA VBLANK  	


;main scanline loop...



PreScanLoop



ScanLoop1 ;start of kernal +++++++++++++++++++++++ for skyline
	LDA PFCOLOR-1,Y		; 4 cycles
	STA COLUBK	;and store as the bgcolor ; 3 cycles
	LDA PFData0-1,Y		; 4 cycles
	STA PF0			; 3 cycles
	LDA PFData1-1,Y		; 4 cycles
	STA RESM0		; 3 cycles places left scan line leftmost
	STA PF1			; 3 cycles
	LDA PFData2-1,Y		; 4 cycles
	STA PF2			; 3 cycles


	LDA #0							;2 cycles =30
	STA GRP1	; put player 1 into grp1 3 cycles 
	STA GRP0	;put that line as player graphic 0	 ;3 cycles =28
	DEY		;count down number of scan lines	  2 cycles =71
	STA WSYNC 						 ;3 cycles =74
	BNE ScanLoop1		 				 ;2 cycles =76
EndScanLoop1 ;end of kernal +++++++++++++++++++++++ for skyline

	LDA #100;

	STA COLUBK	;and store as the bgcolor
	LDY #186 ; was 191 was 186
	LDA #0
	STA PF0			; 3 cycles
	STA PF1			; 3 cycles
	STA PF2			; 3 cycles

	LDA #%11100011	;The last 3 bits control number and size of players
			;the firs 3 bits control missle size
	STA NUSIZ0
	STA NUSIZ1
	STA WSYNC 						 ;3 cycles


ScanLoop ;start of kernal +++++++++++++++++++++++ for players
        ;-------------------------- 
        ; SPRITE DRAW
        tya                     ; 2 Transfers the byte in the Y Register to the Accumulator.
        sec                     ; 2 Sets the carry (C) flag (in the processor Status Register byte).
        sbc SpriteEnd           ; 3 Subtracts a byte in memory from the byte in the Accumulator, and "borrows" if necessary.
        adc #8      		; 2 Adds byte in memory to the byte in the Accumulator, plus the carry flag if set. 
        bcs .Draw               ; 2(3) Branches up to 127 bytes forward or 128 bytes backward from its own address if the carry flag is set. 
        nop                     ; 2 Wait
        nop                     ; 2 Wait
        sec                     ; 2 Sets the carry (C) flag 
        bcs .skipDraw           ; 3 Branches up to 127 bytes forward or 128 bytes backward from its own address if the carry flag is set.
.Draw
        lda MainPlayerGraphics,y          ; 5 Loads the Accumulator with a byte from memory. 
        sta GRP0	          ; 3 Stores the byte in the Accumulator into memory.
.skipDraw
         ;-->18 cycles used
         ;--------------------------

	STA GRP0  	;set player graphics                                  3 cycles
	STA GRP1  	;set player graphics                                  3 cycles




	DEY		;count down number of scan lines	  2 cycles =
	STA WSYNC 						 ;3 cycles =
	BNE ScanLoop		 				 ;2 cycles =
EndScanLoop ;end of kernal +++++++++++++++++ for players


	STA WSYNC  	
	STA VBLANK 	
	LDX #24		



OverScanWait
	STA WSYNC
	DEX
	BNE OverScanWait
	JMP  MainLoop      



MainPlayerGraphics
	.byte #010100
	.byte #010100
	.byte #011000
	.byte #011000
	.byte #%01111110
	.byte #010000
	.byte #111000
	.byte #111000
SpriteEnd

	.byte #100010
	.byte #100100
	.byte #101000
	.byte #011000
	.byte #%01111110
	.byte #010000
	.byte #111000
	.byte #111000



EnemyGraphics
	.byte #%01111000
	.byte #%10000100
	.byte #001000
	.byte #010000
	.byte #010000
	.byte #010000
	.byte #111000
	.byte #111000


	.byte #%01111000
	.byte #%01001000
	.byte #010000
	.byte #100000
	.byte #100000
	.byte #100000
	.byte #%01110000
	.byte #%01110000

PFData0
        .byte #001111
        .byte #011111
        .byte #%01111111
        .byte #%11111111

PFData1
        .byte #000000
        .byte #001110
        .byte #111111
        .byte #%01111111

PFData2
        .byte #000000
        .byte #011000
        .byte #%10111100
        .byte #%11111111

PFCOLOR
	.byte #$5F
	.byte #$5D
	.byte #$5B
	.byte #$59


	org $FFFC
	.word Start
	.word Start

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