;
; Shooting stars by Dennis Fox
;

; Page zero usage

PBASE	=	$CB	;POINTERS TO...
MBASE	=	$CD	;MISSILES,
BASE2	=	$CF	;PLAYER1,
BASE3	=	$D1	;PLAYER2,
BASE4	=	$D3	;PLAYER3
ADDR	=	$D5	;2-BYTE POINTER

; Page 6 usage

X	=	$600
Y	=	$601
XM	=	$610
YM	=	$620
DM	=	$630
T1	=	$640
T2	=	$641
TI1	=	$642
TI2	=	$643
HIT	=	$645
LIFE	=	$650
TI3	=	$660
TI4	=	$6A0
ELF	=	$6A1
SF1	=	$6A2
STIME	=	$6A3

; Operating system equates

ATTRAC	=	$4D	;ATTRACT MODE POINTER
PCOLR0	=	$2C0	;PLAYER COLORS
PCOLR1	=	$2C1
PCOLR2	=	$2C2
PCOLR3	=	$2C3
COLOR0	=	$2C4	;PLAYFIELD COLORS
COLOR1	=	$2C5
COLOR2	=	$2C6
COLOR3	=	$2C7
COLOR4	=	$2C8
SDMCTL	=	$22F	;DMA CONTROL
SDLSTL	=	$230	;DISP LIST POINTER
SDLSTH	=	$231
STICK0	=	$278	;JOYSTICK
STRIG0	=	$284	;STICK BUTTON
HITCLR	=	$D01E	;COLLISION CLEAR
HPOSP0	=	$D000	;P/M HOR. POSITIONS
HPOSP1	=	$D001
HPOSP2	=	$D002
HPOSP3	=	$D003
HPOSM0	=	$D004
HPOSM1	=	$D005
HPOSM2	=	$D006
HPOSM3	=	$D007
M1PL	=	$D009	;COLLISION REGISTERS
M2PL	=	$D00A
M3PL	=	$D00B
P1PL	=	$D00D
P2PL	=	$D00E
P3PL	=	$D00F
GRACTL	=	$D01D	;GRAPHIC CONTROL
CONSOL	=	$D01F	;CONSOLE BUTTONS
AUDF1	=	$D200	;AUDIO CONTROLS
AUDC1	=	$D201
AUDF2	=	$D202
AUDC2	=	$D203
RANDOM	=	$D20A	;RANDOM #
PMBASE	=	$D407	;P/M START ADDR
SETVBV	=	$E45C	;VERT BLANK SET VECTOR
XITVBV	=	$E462	;VERT BLANK EXIT

; set up screen and display list

 ORG $2000

SSTAR	LDX	#9
	LDA	#$FF
SETTB	STA	SCRNA,X	;SET TOP...
	STA	SCRNC,X	;AND BOTTOM...
	DEX		;OF SCREEN
	BPL	SETTB
	LDX	#41
	LDA	#SCRNB/256	;POINT TO...
	STA	ADDR+1	;MIDDLE OF SCREEN
	LDA	#SCRNB&255
	STA	ADDR
SETMID	LDY	#9
MIDLP	LDA	MIDBYT,Y	;COPY MIDDLE BYTES...
	STA	(ADDR),Y	;TO SCREEN RAM
	DEY
	BPL	MIDLP
	LDA	ADDR	;NOW ADD 10 BYTES...
	CLC		;TO POINT TO...
	ADC	#10	;NEXT LINE
	STA	ADDR
	LDA	ADDR+1
	ADC	#0
	STA	ADDR+1
	DEX		;ANOTHER LINE?
	BPL	SETMID	;YES!
	LDA	#DLIST&255	;POINT TO
	STA	SDLSTL	;DISPLAY
	LDA	#DLIST/256	;LIST
	STA	SDLSTH
	LDA	#$00	;SET LOW BYTES...
	STA	MBASE	;OF P/M POINTERS
	STA	PBASE
	STA	BASE2
	STA	BASE3
	STA	BASE4
	LDA	#$33	;NOW SET HI BYTES
	STA	MBASE+1	;TO POINT TO
	LDA	#$34	;VARIOUS P/M AREAS
	STA	PBASE+1
	LDA	#$35
	STA	BASE2+1
	LDA	#$36
	STA	BASE3+1
	LDA	#$37
	STA	BASE4+1

; Set players starting position

START2	LDA	#16	;INITIALIZE TIMERS
	STA	TI1
	STA	TI2
	STA	TI4
	LDA	#$00
	STA	ELF
	STA	SF1
	STA	STIME
	STA	TI3
	LDA	#5	;START W/5 LIVES
	STA	LIFE
START	LDA	#180	;SET UP...
	STA	X	;ASTRONAUT X
	LDA	RANDOM	;NOW GET...
	LSR	A	;RANDOM #
	CLC		;AND SET UP
	ADC	#55	;ASTRONAUT Y
	STA	Y

; Set missles horizontal position

	LDX	#$00	;GET RANDOM...
L1	LDA	RANDOM	;HORIZONTAL
	LSR	A	;POSITION,
	LSR	A	;MAKE SURE IT'S
	ADC	#50	;ON SCREEN,
	STA	XM,X	;STORE IT
	INX		;NEXT MISSILE
	CPX	#6	;ALL DONE?
	BNE	L1	;NOT YET!

; Set missles vertical position

	LDX	#$00	;START W/MISSILE 0
L2	TXA		;GET MISSILE #
	ASL	A	;MULTIPLY...
	ASL	A	;MISSILE...
	ASL	A	;NUMBER...
	ASL	A	;BY 32,
	ASL	A	;MAKE SURE IT'S...
	ADC	#55	;ON SCREEN,
	STA	YM,X	;AND STORE IT!
	INX		;NEXT MISSILE
	CPX	#6	;ALL DONE?
	BNE	L2	;NOT YET!

; Set missiles' starting directions

	LDX	#$00
L3	LDA	RANDOM	;GET RANDOM...
	AND	#$03	;DIRECTION
	STA	DM,X	;AND STORE
	INX		;NEXT MISSILE
	CPX	#6	;ALL DONE?
	BNE	L3	;NOT YET!

; Set up player missile graphics
; Single line resolution

	LDA	#$30	;POINT TO P/M AREA
	STA	PMBASE
	LDA	#62	;TURN ON SCREEN
	STA	SDMCTL
	LDA	#3	;SET P/M GRAPHICS
	STA	GRACTL
	LDA	#$00	;NOW CLEAR OUT...
	TAY		;ALL MISSILES
A1	STA	(PBASE),Y	;AND PLAYERS
	STA	(MBASE),Y
	STA	(BASE2),Y
	STA	(BASE3),Y
	STA	(BASE4),Y
	INY
	BNE	A1
	LDA	#$00	;NO COLLISION!
	STA	HIT
	STA HITCLR
	LDA	#$46	;SET UP COLORS
	STA	PCOLR0
	LDA	#15
	STA	PCOLR1
	STA	PCOLR2
	STA	PCOLR3
	LDA	#150
	STA	COLOR1
	LDA	#54
	STA	COLOR2
	LDA	#$F8
	STA	COLOR0
	LDA	#3
	STA	T2
	LDA	#$07	;NOW START UP...
	LDX	#VBI/256	;OUR VERTICAL BLANK...
	LDY	#VBI&255	;INTERRUPT!
	JSR	SETVBV

; The game begins here

BACK	LDA	CONSOL	;CHECK CONSOLE KEYS
	CMP	#6	;START PRESSED?
	BNE	JOY2	;NOPE!
   	JMP	DEATH	;GO TO RESTART!

; Read joystick

JOY2	LDA	STICK0	;GET ASTRONAUT...
	AND	#1	;DIRECTION
	BNE	O1
	DEC	Y	;UP
O1	LDA	STICK0
	AND	#$08
	BNE	O2
	INC	X	;RIGHT
O2	LDA	STICK0
	AND	#$02
	BNE	O3
	INC	Y	;DOWN
O3	LDA	STICK0
	AND	#$04
	BNE	O4
	DEC	X	;LEFT
O4	LDA	X	;GET ASTRO. X
	CMP	#200	;TOO FAR RIGHT?
	BNE	O5	;IT'S OK
	DEC	X	;TOO FAR!
O5	LDA	X
	CMP	#50	;TOO FAR LEFT?
	BNE	O6	;OK.
	INC	X	;TOO FAR!
O6	LDA	Y	;GET ASTRO. Y
	CMP	#52	;TOO FAR UP?
	BNE	O7	;OK.
	INC	Y	;TOO FAR!
O7	LDA	Y
	CMP	#200	;TOO FAR DOWN?
	BNE	O8	;OK.
	DEC	Y	;TOO FAR!

; Put astronaut on playfield

O8	LDA	X	;GO AHEAD AND SET...
	STA	HPOSP0	;HOR. POSITION
	LDX	#$00	;NOW COPY THE...
	LDY	Y	;ASTRONAUT IMAGE...
B1	LDA	ANAUT,X	;INTO PLAYER 1
	STA	(PBASE),Y
	INX
	INY
	CPX	#19
	BNE	B1

; Move missiles

	LDX	#$00
D0	LDA	DM,X	;GET MISSILE DIR.
	BNE	D1
	INC	XM,X	;RIGHT...
	DEC	YM,X	;AND UP
D1	LDA	DM,X
	CMP	#1
	BNE	D2
	INC	XM,X	;RIGHT...
	INC	YM,X	;AND DOWN!
D2	LDA	DM,X
	CMP	#2
	BNE	D3
	DEC	XM,X	;LEFT...
	INC	YM,X	;AND DOWN!
D3	LDA	DM,X
	CMP	#3
	BNE	DO1
	DEC	XM,X	;LEFT...
	DEC	YM,X	;AND UP!
DO1	INX		;NEXT MISSILE
	CPX	#6	;ALL DONE?
	BNE	D0	;NO, DO OTHERS!

; Check if missile has hit wall

	LDX	#$00
C0	LDA	XM,X	;GET X POS.
	CMP	#202	;TOO FAR RIGHT?
	BNE	C1	;IT'S OK.
	LDA	DM,X	;IT'S TOO FAR,
	BNE	DI1	;WE MUST REVERSE
	LDA	#3	;THE DIRECTION!
	STA	DM,X
	CLC
	BCC	C1
DI1	LDA	#2
	STA	DM,X
C1	LDA	XM,X	;GET X POS.
	CMP	#48	;TOO FAR LEFT?
	BNE	C2	;OK.
	LDA	DM,X	;REVERSE DIRECTION!
	CMP	#2
	BEQ	DI2
	LDA	#0
	STA	DM,X
	CLC
	BCC	C2
DI2	LDA	#1
	STA	DM,X
C2	LDA	YM,X	;GET Y POS.
	CMP	#52	;TOO FAR UP?
	BNE	C3	;OK.
	LDA	DM,X	;REVERSE!
	BNE	DI3
	LDA	#1
	STA	DM,X
	CLC
	BCC	C3
DI3	LDA	#2
	STA	DM,X
C3	LDA	YM,X	;GET Y POS.
	CMP	#213	;TOO FAR DOWN?
	BNE	C4	;OK.
	LDA	DM,X	;REVERSE!
	CMP	#1
	BNE	DY2
	LDA	#$00
	STA	DM,X
	CLC
	BCC	C4
DY2	LDA	#3
	STA	DM,X
C4	INX		;NEXT MISSILE
	CPX	#6	;ALL DONE?
	BNE	C0	;NO, DO OTHERS!

; Plot missiles on playfield

	LDA	XM	;SET ALL MISSILES...
	STA	HPOSP1	;HORIZONTAL...
	LDA	XM+1	;POSITIONS!
	STA	HPOSP2
	LDA	XM+2
	STA	HPOSP3
	LDA	XM+3
	STA	HPOSM1
	LDA	XM+4
	STA	HPOSM2
	LDA	XM+5
	STA	HPOSM3
	LDA	#$00	;PLOT 1ST MISSILE
	LDY	YM	;IN PLAYER 1
	STA	(BASE2),Y
	LDA	#$10
	INY
	STA	(BASE2),Y
	INY
	STA	(BASE2),Y
	LDA	#$00
	INY	
	STA	(BASE2),Y
	LDA	#$00	;PLOT 2ND MISSILE
	LDY	YM+1	;IN PLAYER 2
	STA	(BASE3),Y
	LDA	#$10
	INY
	STA	(BASE3),Y
	INY
	STA	(BASE3),Y
	LDA	#$00
	INY	
	STA	(BASE3),Y
	LDA	#$00	;PLOT 3RD MISSILE
	LDY	YM+2	;IN PLAYER 3
	STA	(BASE4),Y
	LDA	#$10
	INY
	STA	(BASE4),Y
	INY
	STA	(BASE4),Y
	LDA	#$00
	INY	
	STA	(BASE4),Y
	LDA	#$EF	;PLOT 4TH MISSILE
	LDY	YM+3	;IN MISSILE 1
	AND	(MBASE),Y
	STA	(MBASE),Y
	LDA	#$10
	INY
	ORA	(MBASE),Y
	STA	(MBASE),Y
	LDA	#$10
	INY
	ORA	(MBASE),Y
	STA	(MBASE),Y
	LDA	#$EF	;PLOT 5TH MISILE
	INY		;IN MISSILE 2
	AND	(MBASE),Y
	STA	(MBASE),Y
	LDA	#$FB
	LDY	YM+4
	AND	(MBASE),Y
	STA	(MBASE),Y
	LDA	#$04
	INY
	ORA	(MBASE),Y
	STA	(MBASE),Y
	LDA	#$04
	INY
	ORA	(MBASE),Y
	STA	(MBASE),Y
	LDA	#$FB	;PLOT 6TH MISSILE
	INY		;IN MISSILE 3
	AND	(MBASE),Y
	STA	(MBASE),Y
	LDA	#$BF
	LDY	YM+5
	AND	(MBASE),Y
	STA	(MBASE),Y
	LDA	#$40
	INY
	ORA	(MBASE),Y
	STA	(MBASE),Y
	LDA	#$40
	INY
	ORA	(MBASE),Y
	STA	(MBASE),Y
	LDA	#$BF
	INY
	AND	(MBASE),Y
	STA	(MBASE),Y

; Create sound

	INC	T1
	LDA	T1
	CMP	#$10
	BNE	SO1
	LDA	#$00
	STA	T1
	DEC	T2
	LDA	T2
	BNE	SO2
	LDA	#3
	STA	T2
SO2	LDA	#$C8	;SET SOUND CONTROL
	STA	AUDC2
	LDA	T2	;GET SOUND NUMBER
	CMP	#3	;SOUND 3?
	BNE	S2	;NO!
	LDA	#120	;SET 3RD...
	STA	AUDF2	;SOUND FREQUENCY
	CLC
	BCC	SO1	;GO SHOW TIME
S2	LDA	T2
	CMP	#2	;SOUND 2?
	BNE	S3	;NO!
	LDA	#100	;SET 2ND...
	STA	AUDF2	;SOUND FREQUENCY
	CLC
	BCC	SO1	;AND SHOW TIME
S3	LDA	#85	;SET 1ST
	STA	AUDF2	;SOUND FREQUENCY
SO1	LDA	TI1	;SHOW DIGIT 1...
	STA	SCREEN+9	;OF SECONDS
	LDA	TI2	;SHOW DIGIT 2...
	STA	SCREEN+10	;OF SECONDS
	LDA	TI4	;SHOW MINUTES!
	STA	SCREEN+7

; Check for extra life

	LDA	TI4	;GET MINUTES
	CMP	#19	;3 MINUTES?
	BNE	OELC	;NO!
	LDA	ELF	;DONE EXTRA LIFE YET?
	BNE	OELC	;YES, NO MORE!
	INC	LIFE	;ANOTHER LIFE
	INC	ELF	;SET EXTRA LIFE FLAG
	LDA	#$A4	;SET UP FOR...
	STA	AUDC1	;EXTRA LIFE SOUND
	LDA	#$01
	STA	SF1
OELC	LDA	TI4	;GET MINUTES
	CMP	#21	;5 MINUTES?
	BNE	OEL	;NO!
	LDA	ELF	;GOT 2ND EXTRA?
	CMP	#1
	BNE	OEL	;NO MORE!
	INC	LIFE	;ANOTHER LIFE!
	INC	ELF	;INC EXTRA LIFE FLAG
	LDA	#$A4	;SET UP FOR...
	STA	AUDC1	;EXTRA LIFE SOUND
	LDA	#$01
	STA	SF1

; Check for ending sequence

OEL	LDA	HIT	;ASTRO HIT DEBRIS?
	BEQ	NEND	;NO, HE'S OK.
	JMP	END	;UH-OH!
NEND	LDA	#80	;THIS SECTION
	LSR	TI1	;CREATES A TIME
	PHP		;DELAY USING
	SEC		;THE TIME VARIABLES
	SBC	TI1	;TI1 AND TI4
	PLP
	ROL	TI1
	LDX	#$00
SMOR	SBC	TI4
	INX
	CPX	#3
	BNE	SMOR
	TAX
TD1	LDY	#$00	;THIS IS A
TD2	INY		;TIME DELAY
	BNE	TD2	;ROUTINE!
	DEX
	BNE	TD1

; Play extra life sound

	LDA	SF1	;GET BONUS SOUND FLAG
	CMP	#1	;FIRST FREQ?
	BNE	SC2	;NO!
	LDA	#50	;SET 1ST BONUS FREQ.
	STA	AUDF1
	INC	STIME	;INC SOUND TIMER
	LDA	STIME
	CMP	#$25	;END OF SOUND?
	BNE	SC2	;NOT YET!
	INC	SF1	;NEXT FREQ
	LDA	#$00	;NO MORE SOUND!
	STA	STIME
SC2	LDA	SF1	;GET BONUS SOUND FLAG
	CMP	#2	;SECOND FREQ?
	BNE	SC3	;NO!
	LDA	#40	;SET FREQ.
	STA	AUDF1
	INC	STIME	;INCREMENT TIMER
	LDA	STIME
	CMP	#$25	;SOUND DONE?
	BNE	SC3	;NO!
	INC	SF1	;NEXT FREQ
	LDA	#$00	;ALL DONE!
	STA	STIME
SC3	LDA	SF1	;GET BONUS SOUND FLAG
	CMP	#3	;3RD FREQ?
	BNE	SC4	;NO!
	LDA	#32	;SET FREQ.
	STA	AUDF1
	INC	STIME	;INC SOUND TIMER
	LDA	STIME
	CMP	#$25	;SOUND DONE?
	BNE	SC4	;NO!
	INC	SF1	;SET FOR END
	LDA	#$00	;ALL DONE!
	STA	STIME
SC4	LDA	SF1	;GET BONUS SOUND FLAG
	CMP	#4	;END OF SOUND?
	BNE	SC5	;NO!
	LDA	#00	;SHUT OFF SOUND!
	STA	AUDF1
	STA	AUDC1
	LDA	#$00	;ALL DONE!
	STA	STIME
SC5	LDA	#138	;UPDATE LIVES...
	LDX	#$00	;DISPLAY
DMORE	STA	SCREEN+13,X	;ALL LIVES
	INX
	CPX	LIFE
	BNE	DMORE
	JMP	BACK
END	DEC	LIFE	;1 LESS LIFE
	LDA	#$A8	;INIT DEATH SOUND
	STA	AUDC1
	STA	AUDC2
	LDA	#50	;INIT FREQ.
SA	STA	AUDF1
	PHA
	CLC
	ADC	#100	;INCREMENT SOUND
	STA	AUDF2
	STA	PCOLR0	;FLASH ASTRONAUT
	PLA
	LDY	#$00	;TIME DELAY
DLY2	LDX	#$00
DLY1	INX
	BNE	DLY1
	INY
	CPY	#25
	BNE	DLY2
	CLC
	ADC	#$01
	CMP	#100	;END OF DEATH?
	BNE	SA	;NO, LOOP BACK
	LDA	#$00	;SHUT OFF SOUND
	STA	AUDF1
	STA	AUDC1
	STA	AUDF2
	STA	AUDC2
	LDA	#$46	;RESET...
	STA	PCOLR0	;ASTRONAUT COLOR
	LDA	#$00	;REMOVE...
	LDY	LIFE	;LIFE INDICATOR...
	STA	SCREEN+13,Y	;FROM SCREEN
	LDA	LIFE	;ANY MORE LIVES?
	BEQ	DEATH	;NO! END OF GAME!
	JMP	START	;ANOTHER LIFE.
DEATH	LDA	#00	;ZERO LIVES
	STA	LIFE
AGAIN	LDA	STRIG0	;STICK TRIGGER PRESSED?
	BEQ	RESTRT	;YES!
	LDA	CONSOL	;GET CONSOLE KEY
	CMP	#6	;START PRESSED?
	BNE	AGAIN	;NO!
RESTRT	LDA	#$00	;RESET...
	STA	ATTRAC	;ATTRACT MODE
	JMP	START2	;RESTART GAME.

; Vertical blank interrupt

VBI	LDA	M1PL	;GET...
	ORA	M2PL	;ALL...
	ORA	M3PL	;COLLISION...
	ORA	P1PL	;REGISTERS...
	ORA	P2PL	;AND CHECK...
	ORA	P3PL	;FOR...
	AND	#1	;ASTRONAUT...
	STA	HIT	;COLLISION!
	INC	TI3	;INCREMENT 1/60 SEC.
	LDA	TI3	;TIMER
	CMP	#60	;ANOTHER SECOND?
	BNE	TOVR	;NO!
	LDA	#$00	;RESET 60THS OF SEC
	STA	TI3
	INC	TI2	;ANOTHER SECOND
	LDA	TI2
	CMP	#26	;10 SECS?
	BNE	TOVR	;NO!
	LDA	#16	;RESET 2ND SECOND...
	STA	TI2	;DIGIT TO 0
	INC	TI1	;INCREMENT 1ST...
	LDA	TI1	;SECOND DIGIT
	CMP	#22	;GOT A MINUTE?
	BNE	TOVR	;NO!
	INC	TI4	;INCREMENT MINUTES
	LDA	#16	;RESET 1ST SECOND...
	STA	TI1	;DIGIT TO 0
TOVR	JMP	XITVBV	;EXIT VERT BLANK!

; Set up display list

DLIST	DB	112,112,112,71
	DW	SCREEN
	DB	9,9,9,9,9,9,9,9,9,9
	DB	9,9,9,9,9,9,9,9,9,9
	DB	9,9,9,9,9,9,9,9,9,9
	DB	9,9,9,9,9,9,9,9,9,9
	DB	9,9,9,9
	DB	65
	DW	DLIST

; Data for astronaut image

ANAUT	DB	$00,$7C,$54,$6C,$7C,$44,$7C,$10,$10,$FE,$BA,$BA
	DB	$BA,$38,$38,$28,$28,$EE,$00

; Set up screen memory

MIDBYT	DB	128,0,0,0,0,0,0,0,0,1
SCREEN	DB	0,0,116,105,109,101,0,0,26,0,0,0,0,0,0,0,0,0,0,0
SCRNA	DS	10
SCRNB	DS	420
SCRNC	DS	10

	END	SSTAR