*************************
** 3D Stars in Sprites **
** ©'89 MMS of Level 4 **
*************************

	jmp	$30000
	org	$30000		; Startadresse $30000
	load	$30000

Field=	$40000			; Zwischenspeicher
Spr1=	Field+244		; Sprite 1
Spr2=	Spr1+1608		; Sprite 2
Stars=	Spr2+1608		; Koordinaten

Anz=40

o:	move.l	#Start,$80.w
	trap	#0		; Prg runs in TRAP#0
	rts

Start:	move.w	#$2700,sr	; IRQ out / Supervisor
	move.w	#$8400,$96(a5)
	clr.l	0		; Other sprites off !
	lea.l	$dff000,a5
	bsr.L	Init_Stars	; Initizate Routine
	move.l	#Copper,$80(a5)

Sync:	cmp.b	#$f1,$6(a5)	; Auf Rasterzeile $f1 warten
	bne.s	sync

	move.w	#$0fff,$180(a5)	; Col00 = weiss

	bsr.L	Write_Stars	; Calculate Pos. + Write in Sprites
	bsr.L	Move_Stars	; Move Stars

	move.w	#$0000,$180(a5)	; Col00 = schwarz

	and.b	#$40,$bfe001	; Mouse button ?
	bne.s	Sync

	lea.l	GfxName,a1	; Open GFX library
	move.l	4.w,a6
	jsr	-408(a6)
	move.l	d0,a1
	move.l	$26(a1),$80(a5)	; old Copper
	jsr	-414(a6)	; Close GFX library
	rte

GfxName:dc.b	"graphics.library",0
even
Copper:	dc.w	$0180,$0000,$0182,$0000
	dc.w	$008e,$2900,$0090,$f1ff,$0092,$0038,$0094,$00d0
	dc.w	$0100,$1200,$00e0,$0000,$00e2,$0000
	
	dc.w	$0120,spr1/$10000,$0122,spr1		; Sprite0
	dc.w	$0124,spr2/$10000,$0126,spr2		; Sprite1
	dc.w	$01a2,$0fff,$01a4,$0888,$01a6,$0333	; SprCol0+1

	dc.w	$0128,$0000,$012a,$0000,$012c,$0000,$012e,$0000
	dc.w	$0130,$0000,$0132,$0000,$0134,$0000,$0136,$0000
	dc.w	$0138,$0000,$013a,$0000,$013c,$0000,$013e,$0000
	dc.w	$ffff,$fffe

Rnd:	move.w	$6(a5),d0
	muls	Zufall,d0
	move.w	d0,Zufall
	add.w	#$4123,Zufall
	rts

Zufall:	dc.w	$1234,$0

Init_Stars:
	lea.l	Stars,a0
	move.w	#Anz,d7
StarField:
	moveq	#0,d0
	bsr.s	Rnd
	move.b	d0,(a0)+	;Set x
	bsr.s	Rnd
	move.b	d0,(a0)+	;Set y
Try_z:	bsr.s	Rnd
	cmp.b	#4,d0
	bmi.s	Try_z
	move.b	d0,(a0)+	;Set z
	dbf	d7,StarField
	rts

Write_Stars:
	move.w	#$0100,$40(a5)	; Clear Field
	move.l	#Field+$28,$54(a5)
	move.w	#0,$66(a5)
	move.w	#[101*64]+1,$58(a5)

	lea.l	Field,a0
	lea.l	Stars,a2
	move.w	#Anz,d7
Writie:	move.b	(a2)+,d0	;x->d0
	move.b	(a2)+,d1	;y->d1
	move.b	(a2)+,d2	;z->d2
	lsr.w	#2,d2
	ext.w	d0
	ext.w	d1
	ext.l	d0
	ext.l	d1

	divs	d2,d0		;x/z
	divs	d2,d1		;y/z

	add.b	#144,d0		; x mitte
	add.b	#141,d1		; y mitte
	and.w	#$ff,d1
	move.b	d0,(a0,d1.w)	; Write in Field
	dbf	d7,Writie

	lea.l	Spr1,a0		; Write in Sprite0+1
	lea.l	Spr2,a1
	lea.l	Field,a2
	move.w	#$29,d1
	move.w	#99,d7		; 200 Zeilen !
Writy:	move.b	(a2,d1.w),d0
	beq.s	NextSpr
	move.b	d1,(a0)+
	move.b	d0,(a0)+
	addq.b	#1,d1
	move.b	d1,(a0)+
	move.b	#0,(a0)+
	move.l	#$a800d800,(a0)+; Shit pattern (proves Sprites!)
	subq.b	#1,d1
NextSpr:addq.b	#1,d1
	move.b	(a2,d1.w),d0
	beq.s	EndSpr
	move.b	d1,(a1)+
	move.b	d0,(a1)+
	addq.b	#1,d1
	move.b	d1,(a1)+
	move.b	#0,(a1)+
	move.l	#$a800d800,(a1)+
	subq.b	#1,d1
EndSpr:	addq.b	#1,d1
	dbf	d7,Writy
	move.l	#0,(a0)		; Sprites over
	move.l	#0,(a1)
	rts

Move_Stars:
	lea.l	Stars,a0
	move.w	#Anz,d7
Movete:	sub.b	#1,2(a0)	; Move'em
	cmp.b	#4,2(a0)
	bge.s	NochNix
	move.b	#$80,2(a0)	; z=128
	bsr.L	Rnd
	move.b	d0,(a0)		; x=rnd
	bsr.L	Rnd
	move.b	d0,1(a0)	; y=rnd
NochNix:lea	3(a0),a0
	dbf	d7,Movete
	rts