3 replies to this topic

[Primordial Ooze]

I have started writing my remake of pong tentitivly called 6502Pong. I managed to get the player paddles to show onscreen, but for some reason the ball is drawn, it seems to have holes in them. I double checked my assembly code and everything seems to be in order. Any help would be greatly appreciated.

Sincerely,

6502Pong

Attached Files

•  6502Pong.zip   3.04K   89 downloads

[Wickeycolumbus]

I found the problem and fixed it for you

	ldx #0		;get X ready to disable Ball object
								  ;changed from lda to ldx



;	sta ENABL		; removed this line

				; if the visibleballline is non zero,

	lda visibleballline	; if the visibleballline is zero
	beq FinishBall		; don't draw the ball

	lda #2			; otherwise set the accumulator to 2		
	sta ENABL		; and draw the ball
	dec visibleballline	; and decrement the visibleballline by 1
	.byte $2c	;skip over next two bytes. Added this line

FinishBall
	stx ENABL	;this 2 byte instruction is skipped if 
			;ball is still drawing.  changed from sta to stx

Attached Files

•  6502Pong.zip   3.46K   84 downloads

[Nukey Shay]

It can be simplified further, since the FinishBall tag is only branched to when visibleballline is zero (and subsequently, not drawing the ball). There is a 6-cycle difference between the two cases tho...but that doesn't matter here.

SkipActivateBall

	lda visibleballline	; if the visibleballline is zero

	beq FinishBall		; don't draw the ball
	
	lda #2			; otherwise set the accumulator to 2		

	dec visibleballline	; and decrement the visibleballline by 1

FinishBall
	sta ENABL		; enable/disable the ball
				; if the visibleballline is non zero,
				; we're drawing it

[Nukey Shay]

BTW is there a reason for using 8-bit sprite GFX for the players? You could make a shorter kernel by using the missiles instead (and resetting the stack pointer to the missiles and ball to enable/disable them).