update some graphics examples

graphics/gr/checkers/checkers.s

@@ -1,13 +1,14 @@
-; Checkers, based on the code in Hellmood's Memories
+; Checkers
+; vaguely based on a scene in Hellmood's Memories
 
-; 42 bytes
-; could be shorter if you're not picky about colors
+; 32 bytes, for Lovebyte 2021
 
 ; by deater (Vince Weaver) <vince@deater.net>
 
 ; 42 -- original
 ; 39 -- not fullscreen
 ; 36 -- now marches oddly
+; 32 -- colors now rainbow
 
 ; Zero Page
 BASL		= $28
@@ -55,8 +56,7 @@ checkers:
 	; init screen
 	jsr	SETGR				; 3
 ;	bit	FULLGR				; 3
-						;====
-						; 6
+
 checkers_forever:
 
 	inc	FRAME				; 2
@@ -79,7 +79,8 @@ xloop:
 ;	sbc	#0
 
 	eor	X2
-;	ora	#$DB
+
+;	ora	#$DB	; needed for solid colors
 ;	adc	#1
 
 	jsr	SETCOL

graphics/gr/plasma/plasma.s

@@ -1,4 +1,10 @@
-; do a (hopefully fast) plasma type demo
+; A 123-byte Apple II Lo-res Fake Palette Rotation Demo
+;	The Apple II has no Palette rotation hardware, so we fake it
+
+; For Lovebyte 2021
+
+; by Vince `deater` Weaver (vince@deater.net) / dSr
+; with some help from qkumba
 
 ; 151 -- original
 ; 137 -- optimize generation
@@ -22,11 +28,14 @@
 ; 132 -- make lookup 8*sin+7
 ; 131 -- re-arrange sine table
 ; 128 -- call into PLOT for MASK seting
+
+; urgh lovebyte wants 124 byte (counts header)
+
 ; 127 -- base YY<<16 by adding smc, not by shifting
 ; 125 -- realize that the top byte wraps so no need to and
 ; 124 -- re-arrange code to make an CLC unnecessary
+; 123 -- qkumba noticed we can use the $FF offset directly in page flip
 
-; urgh lovebyte wants 124 byte (counts header)
 
 ; zero page
 GBASL	= $26
@@ -115,13 +124,15 @@ flip_pages:
 
 ;	ldy	#0
 
-	iny			; y is $FF, make it 0
+;	iny			; y is $FF, make it 0
 
 	lda	draw_page_smc+1	; DRAW_PAGE
-	beq	done_page
-	iny
+	bne	done_page
+	dey
 done_page:
-	ldx	PAGE1,Y		; set display page to PAGE1 or PAGE2
+;	ldx	PAGE1,Y		; set display page to PAGE1 or PAGE2
+
+	ldx	$BF56,Y		; PAGE1 - $FF
 
 	eor	#$4		; flip draw page between $400/$800
 	sta	draw_page_smc+1 ; DRAW_PAGE

graphics/gr/sier/Makefile

@@ -3,11 +3,12 @@ include ../../../Makefile.inc
 DOS33 = ../../../utils/dos33fs-utils/dos33
 TOKENIZE = ../../../utils/asoft_basic-utils/tokenize_asoft
 LINKERSCRIPTS = ../../../linker_scripts
+EMPTY_DISK = ../../../empty_disk/empty.dsk
 
 all:	sier.dsk
 
 sier.dsk:	HELLO SIER SIER_TINY SIER_64
-	cp empty.dsk sier.dsk
+	cp $(EMPTY_DISK) sier.dsk
 	$(DOS33) -y sier.dsk SAVE A HELLO
 	$(DOS33) -y sier.dsk BSAVE -a 0x36C SIER
 	$(DOS33) -y sier.dsk BSAVE -a 0x300 SIER_TINY

graphics/gr/sier/sier_64.s

@@ -1,6 +1,7 @@
 ; fake sierpinski
+; 64-byte Apple II demo
 
-; scrolling and colors
+; with scrolling and colors
 
 ; by Vince `deater` Weaver, dSr, Lovebyte 2021
 
@@ -55,30 +56,24 @@ sier_xloop:
 	clc
 	adc	FRAME
 
-;	sta	X2
-;	lda	XX
-;	adc	FRAME
-;	and	X2
-
 	and	XX
 
 	bne	black
-;	lda	#$11	; red
-	lda	FRAME
+	lda	FRAME		; color is based on frame
 	lsr
 	lsr
 	lsr
 	lsr
-	bne	not_zero
-	lda	#3
+	bne	not_zero	; but no color 0 (would be all black)
+	lda	#3		; how about purple instead
 
 not_zero:
 
 	.byte	$2C	; bit trick
 black:
 	lda	#$00
-;	sta	COLOR
-	jsr	SETCOL
+
+	jsr	SETCOL		; set top/bottom nibble same color
 
 	ldy	XX
 	txa