gr: stars_bot: optimizing

2025-02-23 20:29:15 +00:00 · 2022-05-31 12:55:41 -04:00 · 2022-05-31 12:55:41 -04:00 · 105148be9d
commit 105148be9d
parent c6a325c25d
1 changed files with 240 additions and 0 deletions
--- a/graphics/gr/sprite/stars_bot.s
+++ b/graphics/gr/sprite/stars_bot.s
@ -0,0 +1,240 @@
+; bouncing stars
+
+; by Vince `deater` Weaver
+
+; 119 bytes -- single star original
+; 143 bytes -- three stars
+; 141 bytes -- optimize init
+; 140 bytes -- 0 is already in X
+; 143 bytes -- stars move independently
+; 140 bytes -- optimize XPOS in multiple calls to draw_stars
+; 145 bytes -- color changing background
+; 139 bytes -- re-inline draw_star
+; 143 bytes -- speed up the color transition
+; 144 bytes -- tried to share adjust_page in subroutine, backfired
+; 143 bytes -- revert last change
+
+SPEAKER		= $C030
+SET_GR		= $C050
+SET_TEXT	= $C051
+FULLGR		= $C052
+PAGE1		= $C054
+PAGE2		= $C055
+LORES		= $C056		; Enable LORES graphics
+
+HGR2		= $F3D8
+PLOT		= $F800		; PLOT AT Y,A (A colors output, Y preserved)
+GBASCALC	= $F847		; Y in A, put addr in GBASL/GBASH
+SETGR		= $FB40
+WAIT		= $FCA8		; delay 1/2(26+27A+5A^2) us
+
+GBASL		= $26
+GBASH		= $27
+
+YPOS		= $76
+XPOS		= $77
+
+FRAME		= $6D
+PAGE		= $6E
+
+
+;.zeropage
+;.globalzp	pattern_smc
+
+
+stars:
+	jsr	HGR2		; sets graphics/full-screen/hires/PAGE2
+				; sets A and Y to 0
+
+	bit	LORES		; switch to lo-res mode
+
+	; A should be 0 here
+
+main_loop:
+	sta	PAGE	; save PAGE value (PAGE in A here)
+
+	asl		; make OUTH $4 or $8 depending on value in PAGE
+			; which we have in A above or at end of loop
+	asl		; C is 0
+	adc	#4
+
+	sta	GBASH
+
+	inc	FRAME	; increment frame #
+	lda	FRAME
+	and	#$1f	; cycle colors ever 32 frames
+	bne	no_cs
+
+	inc	bg_smc+1
+
+no_cs:
+
+	lda	#100	; pause a bit
+	jsr	WAIT
+
+	sta	GBASL	; A is 0
+
+
+	;=================================
+	; clear lo-res screen, page1/page2
+	;=================================
+	; proper with avoiding screen holes is ~25 instructions
+
+	ldx	#4		; lores is 1k, so 4 pages
+;	stx	GBASH
+;	jsr	adjust_page
+full_loop:
+	ldy	#$00		; clear whole page
+bg_smc:
+	lda	#$54		; color
+inner_loop:
+	sta	(GBASL),Y
+	dey
+	bne	inner_loop
+
+	inc	GBASH		; point to next page
+	dex
+	bne	full_loop
+
+
+	;====================
+	; draw the stars
+	;====================
+
+	txa			; X is zero here
+
+	;======================
+	; draw 8x8 bitmap star
+	;======================
+	; A is XPOS on entry
+draw_star:
+
+	; calculate YPOS
+	sta	XPOS
+
+;	lda	XPOS
+	lsr			; make middle star offset+4 from others
+	lsr
+
+	adc	FRAME		; look up bounce amount
+	and	#$7
+	tax
+	lda	bounce,X
+	sta	YPOS
+
+
+	ldx	#7		; draw 7 lines
+boxloop:
+	txa
+	clc
+	adc	YPOS
+	jsr	GBASCALC	; calc address of line in X (Y-coord)
+
+
+	; GBASL is in A at this point
+
+	clc
+	adc	XPOS		; adjust to X-coord
+	sta	GBASL
+
+	; adjust for proper page
+
+;	jsr	adjust_page
+
+	lda	PAGE		; want to add 0 or 4 (not 0 or 1)
+	asl
+	asl			; this sets C to 0
+	adc	GBASH
+	sta	GBASH
+
+	;=================
+	; draw line
+
+
+	ldy	#7		; 8-bits wide
+	lda	bitmap,X	; get low bit of bitmap into carry
+draw_line_loop:
+	lsr
+
+	pha
+
+	bcc	its_transparent
+
+	lda	#$dd		; yellow
+	sta	(GBASL),Y	; draw on screen
+its_transparent:
+
+	pla
+
+	dey
+	bpl	draw_line_loop
+
+	dex
+	bpl	boxloop
+
+	lda	XPOS
+	clc
+	adc	#16
+
+	cmp	#48
+	bne	draw_star
+
+
+	; X is $FF here
+	; Y is $FF here
+	; A is 48 here
+
+	;======================
+	; flip page
+	;======================
+
+	lda	PAGE
+
+	tax
+	ldy	PAGE1,X			; flip page
+
+	eor	#$1			; invert (leaving in A)
+
+	bpl	main_loop		; bra
+
+
+	; GBASL in A
+;adjust_page:
+;	sta	GBASL
+;	lda	PAGE		; want to add 0 or 4 (not 0 or 1)
+;	asl
+;	asl			; this sets C to 0
+;	adc	GBASH
+;	sta	GBASH
+;	rts
+
+
+
+; star bitmap
+
+;012|456|
+;   @     ;
+;   @@    ;
+;   @@@@@ ;
+;@@@@@@@  ;
+; @@@@@   ;
+;  @@@@@  ;
+; @@  @@  ;
+;@@    @@ ;
+
+bitmap:
+	.byte $10
+	.byte $18
+	.byte $1f
+	.byte $fe
+	.byte $7c
+	.byte $3e
+	.byte $66
+	.byte $C3
+
+bounce:
+	.byte 10,11,12,13,13,12,11,10
+
+	; for apple II bot
+
+	jmp	stars