From 87699520433782eed72e3df1b2a100b6a6239167 Mon Sep 17 00:00:00 2001
From: Vince Weaver <vincent.weaver@maine.edu>
Date: Wed, 12 Jan 2022 15:58:21 -0500
Subject: [PATCH] flyer: get to fit

---
 demos/l/flyer_512/flyer.s        | 59 +++++++++++++++++++-------------
 demos/l/flyer_512/tracker_init.s |  6 ++--
 2 files changed, 39 insertions(+), 26 deletions(-)

diff --git a/demos/l/flyer_512/flyer.s b/demos/l/flyer_512/flyer.s
index 6173c8c3..2e9ab5a0 100644
--- a/demos/l/flyer_512/flyer.s
+++ b/demos/l/flyer_512/flyer.s
@@ -16,20 +16,25 @@
 ; 504 bytes -- tail call in xdraw
 ; 512 bytes -- switch color with music
 ; 510 bytes -- unneeded reload of A
+; 517 bytes -- made flyer go back and forth
+; 512 bytes -- removed extra cc, merged to common ZP zero init
 
 ; zero page locations
 
 AY_REGS		= $70
-SONG_OFFSET	= $82
-SONG_COUNTDOWN	= $83
+FRAME		= $80
+SONG_OFFSET	= $81
+SONG_COUNTDOWN	= $82
+
 
 HGR_COLOR	= $E4
 HGR_PAGE	= $E6
 HGR_SCALE	= $E7
 HGR_ROTATION	= $F9
+FRAME2		= $DC
 HORIZON_Y	= $FD
 HORIZON_LINE	= $FE
-FRAME		= $FF
+
 
 ; soft-switches
 KEYPRESS	= $C000
@@ -58,7 +63,8 @@ XDRAW0	= $F65D
 flyer:
 
 	jsr	HGR2			; HGR2		HGR_PAGE=$40
-	sta	FRAME			; A=0, Y=0 after HGR2
+;	sta	FRAME			; A=0, Y=0 after HGR2
+					; init by mockingboard init
 
 	;===================
 	; music Player Setup
@@ -186,15 +192,20 @@ horizon_lines_loop:
 	lda	#2
 	sta	HGR_SCALE	; SCALE=2
 
-	; set X based on frame
-	; FIXME: would really prefer sine
+	;====================
+	; move ship
 
-	lda	FRAME
-	and	#$f
-	clc			; not necessary?
-	adc	#140		; X=140+frame&15
+	inc	FRAME2
+	lda	FRAME2
+	and	#$7
+	tay
+
+	ldx	positions,Y
+	;=========================
+	; draw ship
+
+;	ldx	#140
 
-	tax
 	lda	#180		; Y=180
 	jsr	xdraw
 
@@ -209,15 +220,18 @@ horizon_lines_loop:
 	cmp	#84			; if (J>84) then J=0
 	bcc	no_reset_frame		; bge
 
-	lda	#$F4			; -12
+	; we know carry is set here
+	lda	#$F3			; (-13) -12-C
 
 no_reset_frame:
-	clc				; J=J+12
-	adc	#12
+	; we know carry is clear here
+	adc	#12			; J=J+12
 
 	sta	FRAME
 
 
+	;=======================
+	; check for keypress
 check_keypress:
 	lda	KEYPRESS
 	bmi	quiet
@@ -229,12 +243,7 @@ quiet:
 	sta	AY_REGS+7
 
 end:
-	bne	end
-
-
-
-
-
+	brk				; end?
 
 
 
@@ -274,8 +283,12 @@ ship_table:
 	.byte	$0E	; 00 001 110	NDN RT X
 	.byte	$0
 
+
+positions:
+	;	 +4   +8  +8  +4
+	.byte  170,174,182,190,194,190,182,174
+
+.include        "interrupt_handler.s"
+.include	"mockingboard_constants.s"
 ; music
 .include	"mA2E_3.s"
-.include        "interrupt_handler.s"
-; must be last
-.include	"mockingboard_constants.s"
diff --git a/demos/l/flyer_512/tracker_init.s b/demos/l/flyer_512/tracker_init.s
index b77199a5..35f3d151 100644
--- a/demos/l/flyer_512/tracker_init.s
+++ b/demos/l/flyer_512/tracker_init.s
@@ -3,10 +3,10 @@ tracker_init:
 	; setup initial ay-3-8910 values (this depends on song)
 
 init_registers_to_zero:
-	ldx	#13
+	ldx	#$13			; init past end to zero others too
 	lda	#0
-	sta	SONG_OFFSET		; also init song stuff
-	sta	SONG_COUNTDOWN
+;	sta	SONG_OFFSET		; also init song stuff
+;	sta	SONG_COUNTDOWN
 init_loop:
 	sta	AY_REGS,X
 	dex