From 26935161906772c6e3ae4b821fad239ad737c420 Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Mon, 31 Dec 2018 11:29:12 -0500
Subject: [PATCH] fire_tiny: shave some more bytes off by reducing lookup table

---
 fire/Makefile      |  14 ++++-
 fire/cool_effect.s | 154 +++++++++++++++++++++++++++++++++++++++++++++
 fire/fire_tiny.s   |  57 ++++++++++++-----
 3 files changed, 208 insertions(+), 17 deletions(-)
 create mode 100644 fire/cool_effect.s

diff --git a/fire/Makefile b/fire/Makefile
index b70a71bb..a2631bde 100644
--- a/fire/Makefile
+++ b/fire/Makefile
@@ -6,10 +6,11 @@ PNG_TO_RLE = ../gr-utils/png2rle
 
 all:	fire.dsk
 
-fire.dsk:	FIRE FIRE_TINY HELLO
+fire.dsk:	FIRE FIRE_TINY HELLO COOL_EFFECT
 	$(DOS33) -y fire.dsk SAVE A HELLO
 	$(DOS33) -y fire.dsk BSAVE -a 0x1000 FIRE
 	$(DOS33) -y fire.dsk BSAVE -a 0x70 FIRE_TINY
+	$(DOS33) -y fire.dsk BSAVE -a 0x70 COOL_EFFECT
 
 ####
 
@@ -29,6 +30,15 @@ fire_tiny.o:	fire_tiny.s
 	ca65 -o fire_tiny.o fire_tiny.s -l fire_tiny.lst
 
 
+####
+
+COOL_EFFECT:	cool_effect.o
+	ld65 -o COOL_EFFECT cool_effect.o -C ../linker_scripts/apple2_70.inc
+
+cool_effect.o:	cool_effect.s
+	ca65 -o cool_effect.o cool_effect.s -l cool_effect.lst
+
+
 
 ####
 
@@ -39,6 +49,6 @@ HELLO:  hello.bas
 #####
 
 clean:		
-		rm -f *~ *.o *.lst FIRE FIRE_TINY HELLO
+		rm -f *~ *.o *.lst FIRE FIRE_TINY COOL_EFFECT HELLO
 
 
diff --git a/fire/cool_effect.s b/fire/cool_effect.s
new file mode 100644
index 00000000..71f1c080
--- /dev/null
+++ b/fire/cool_effect.s
@@ -0,0 +1,154 @@
+; Lo-res fire animation, size-optimized
+
+; by deater (Vince Weaver) <vince@deater.net>
+
+; based on code described here http://fabiensanglard.net/doom_fire_psx/
+
+; 611 bytes at first
+; 601 bytes -- strip out some unused code
+; 592 bytes -- don't init screen
+; 443 bytes -- remove more dead code
+; 206 bytes -- no need to clear screen
+; 193 bytes -- un-cycle exact the random16 code
+; 189 bytes -- more optimization of random16 code
+; 161 bytes -- move to 8-bit RNG
+; 152 bytes -- reduce lookup to top half colors (had to remove brown)
+;		also changed maroon to pink
+; 149 bytes -- use monitor GR
+; 149 bytes -- load into zero page
+; 140 bytes -- start using zero-page addressing
+; 139 bytes -- rotate instead of mask for low bit
+; 138 bytes -- bcs instead of jmp
+; 137 bytes -- BIT nop trick to get rid of jump
+; 135 bytes -- push/pull instead of saving to zero page
+
+; Zero Page
+SEEDL		= $4E
+TEMP		= $00
+TEMPY		= $01
+
+; 100 = $64
+
+; Soft Switches
+SET_GR	= $C050 ; Enable graphics
+FULLGR	= $C052	; Full screen, no text
+LORES	= $C056	; Enable LORES graphics
+
+; monitor routines
+GR	=	$F390
+
+fire_demo:
+
+	; GR part
+	jsr	GR							; 3
+	bit	FULLGR							; 3
+								;==========
+								;         6
+
+
+	; Setup white line on bottom
+
+	lda	#$ff							; 2
+	ldy	#39							; 2
+white_loop:
+	sta	$7d0,Y			; hline 24 (46+47)		; 3
+	dey								; 1
+	bpl	white_loop						; 2
+								;============
+								;        10
+
+fire_loop:
+
+	ldx	#44			; 22 * 2			; 2
+
+yloop:
+	; low bytes of address
+	lda	<gr_offsets,X						; 2
+	sta	<smc2+1							; 2
+	lda	<gr_offsets+2,X						; 2
+	sta	<smc1+1							; 2
+
+	dec	<smc2+2
+	dec	<smc1+2
+
+	stx	TEMPY	; txa/pha not any better			; 2
+
+	; high bytes of address
+;	lda	<gr_offsets+1,X						; 2
+;	sta	<smc2+2							; 2
+
+	ldx	<smc2+2							; 2
+	dex								; 1
+	txa								; 1
+	ora	#$4		; make sure it's 4-7			; 2
+	sta	<smc2+2							; 2
+
+
+	lda	<gr_offsets+3,X						; 2
+	sta	<smc1+2							; 2
+
+	ldy	#39							; 2
+xloop:
+smc1:
+	lda	$7d0,Y							; 3
+	pha			; save on stack				; 1
+	and	#$7		; mask off				; 2
+	tax								; 1
+
+	;=============================
+	; random8
+	;=============================
+	; 8-bit 6502 Random Number Generator
+	; Linear feedback shift register PRNG by White Flame
+	; http://codebase64.org/doku.php?id=base:small_fast_8-bit_prng
+
+random8:
+	lda	SEEDL
+	beq	doEor
+	asl
+	beq	noEor	; if the input was $80, skip the EOR
+	bcc	noEor
+doEor:	eor	#$1d
+noEor:	sta	SEEDL
+
+	; end inlined RNG
+
+	ror			; shift into carry			; 1
+
+	pla								; 1
+
+	bcs	no_change						; 2
+
+	.byte	$2c	; BIT trick, nops out next instruction
+no_change:
+	lda	<color_progression,X					; 2
+
+smc2:
+	sta	$750,Y							; 3
+	dey								; 1
+	bpl	xloop							; 2
+
+	ldx	TEMPY
+
+	dex
+	dex
+	bpl	yloop
+
+	bmi	fire_loop
+
+
+color_progression:
+	.byte	$00	; 8->0		; 1000 0101
+	.byte	$bb	; 9->11		; 1001 0001
+	.byte	0	; 10->0		; 1010 0000
+	.byte	$aa	; 11->10	; 1011 0000
+	.byte	0	; 12->0		; 1100 0000
+	.byte	$99	; 13->9		; 1101 1001
+	.byte	$00	; 14->0		; 1110 0000
+	.byte	$dd	; 15->13	; 1111 1101
+
+gr_offsets:
+	.word	$400,$480,$500,$580,$600,$680,$700,$780
+	.word	$428,$4a8,$528,$5a8,$628,$6a8,$728,$7a8
+	.word	$450,$4d0,$550,$5d0,$650,$6d0,$750,$7d0
+
diff --git a/fire/fire_tiny.s b/fire/fire_tiny.s
index 9f1813f0..b5bc58d0 100644
--- a/fire/fire_tiny.s
+++ b/fire/fire_tiny.s
@@ -21,9 +21,12 @@
 ; 138 bytes -- bcs instead of jmp
 ; 137 bytes -- BIT nop trick to get rid of jump
 ; 135 bytes -- push/pull instead of saving to zero page
+; 134 bytes -- replace half of lookup table with math
+; 119 bytes -- replace that half of lookup table with better math
 
 ; Zero Page
 SEEDL		= $4E
+TEMP		= $00
 TEMPY		= $01
 
 ; 100 = $64
@@ -58,24 +61,45 @@ white_loop:
 
 fire_loop:
 
-	ldx	#44			; 22 * 2			; 2
+	ldx	#22			; 22				; 2
 
 yloop:
+	; low bytes of address
 	lda	<gr_offsets,X						; 2
-	sta	<smc2+1							; 2
+	sta	<smc_sta+1						; 2
 	lda	<gr_offsets+1,X						; 2
-	sta	<smc2+2							; 2
-	lda	<gr_offsets+2,X						; 2
-	sta	<smc1+1							; 2
-	lda	<gr_offsets+3,X						; 2
-	sta	<smc1+2							; 2
+	sta	<smc_lda+1						; 2
+
+	stx	TEMPY	; txa/pha not any better			; 2
+
+	; high bytes of address
+;	lda	<gr_offsets+1,X						; 2
+;	sta	<smc2+2							; 2
+
+;	lda	<gr_offsets+3,X						; 2
+;	sta	<smc1+2							; 2
+
+	txa								; 1
+	and	#$7
+	lsr								; 1
+	ora	#$4							; 2
+	sta	<smc_sta+2						; 2
+
+	inx								; 1
+	txa								; 1
+	and	#$7
+	lsr								; 1
+	ora	#$4							; 2
+	sta	<smc_lda+2						; 2
+
+
+
 
-	stx	TEMPY							; 2
 
 	ldy	#39							; 2
 xloop:
-smc1:
-	lda	$7d0,Y							; 3
+smc_lda:
+	lda	$8d0,Y							; 3
 	pha			; save on stack				; 1
 	and	#$7		; mask off				; 2
 	tax								; 1
@@ -108,14 +132,13 @@ noEor:	sta	SEEDL
 no_change:
 	lda	<color_progression,X					; 2
 
-smc2:
+smc_sta:
 	sta	$750,Y							; 3
 	dey								; 1
 	bpl	xloop							; 2
 
 	ldx	TEMPY
 
-	dex
 	dex
 	bpl	yloop
 
@@ -133,7 +156,11 @@ color_progression:
 	.byte	$dd	; 15->13	; 1111 1101
 
 gr_offsets:
-	.word	$400,$480,$500,$580,$600,$680,$700,$780
-	.word	$428,$4a8,$528,$5a8,$628,$6a8,$728,$7a8
-	.word	$450,$4d0,$550,$5d0,$650,$6d0,$750,$7d0
+;	.word	$400,$480,$500,$580,$600,$680,$700,$780
+;	.word	$428,$4a8,$528,$5a8,$628,$6a8,$728,$7a8
+;	.word	$450,$4d0,$550,$5d0,$650,$6d0,$750,$7d0
+
+	.byte	$00,$80,$00,$80,$00,$80,$00,$80
+	.byte	$28,$a8,$28,$a8,$28,$a8,$28,$a8
+	.byte	$50,$d0,$50,$d0,$50,$d0,$50,$d0