asteroids-7800/MAIN.S

*         2100    030784
*
*
** MAIN.S **
** ASTEROIDS FOR THE ATARI 3600 *
** THIS FILE CONTAINS THE MAIN DRIVER. **
	.ORG	$D000	        ;MUST BE ON ODD (BLANK HOLY DMA) 4K PAG
CODE:

ASTEROID:
	SEI		        ;AND AWAY WE GO.....
	CLD

	LDA     #$13	        ;LOCK INTO MARIA MODE, base unit rom
				; *AND* DISCHARGE PADDLE INPUT CAPS
	STA     PTCTRL	        ;STORE TO INPTCTRL

	LDX     #$FF		;SET UP THE STACK POINTER
	TXS

	LDX     #$60
	STX     CTRL		;OFF DMA

	LDA     #$14		;SET JOYSTICK DIRECTION REGISTER
	STA     CTLSWB		;TO SELECT TWO BUTTON MODE

	LDA     #0
	STA     BACKGRND	;BLACK BACKGROUND
	STA     OFFSET		;FOR FUTURE EXPANSION
	STA     SWCHB		;SELECT TWO BUTTON MODE
;
	JSR     ZERORAM		;ZERO OUT RAM

	LDA     INTIM		;SEED RANDOM PTRS FROM TIMER
	AND     #31		; ROUGHLY RANGE IT (NOTE: PTR1 MAY GO
	STA     RANDPTR0	; OUT OF RANGE HERE, BUT IT'S OK AS
	CLC			; LONG AS PTR0 DOESN'T GO OUT OF RANGE)
	ADC     #31		;31 IS A GOOD NUMBER FOR THIS
	STA     RANDPTR1

	LDX     #54		;DROP SOME CODE IN TO INIT RAND ARRAY
DROPCODE:
	LDA     CODE,X		;CODE IS PRETTY RANDOM.
	STA     RAND,X		;AT LEAST OURS IS.
	DEX
	BPL     DROPCODE

	LDA     #1		;SET UP MODE/DIFF
	STA     DIFF
	STX     MODE
*
	JSR     HSCSUCK		;SUCK IN HIGH SCORE, IF POSSIBLE
	JSR     INITSCOR	;INITIALIZE SCORES
	JSR     LOADSTAR

	LDA     #$00		;UNLOCK DISCHARGE TRANSISTOR FROM
	STA     $0001		; PADDLE INPUT CAPS.


	LDA     #TITLEST	;INITIALIZE GAME STATE
				;FALL THROUGH INTO....
* PROGRAM DRIVER STATE CHANGER: JMP HERE WITH NEW GAME STATE IN AC.
NEWDRVR:
	STA	GAMSTATE
	LDX	#$FF		;MASH OUT THE STACK POINTER
	TXS
	INX			;INITIALIZE DTIMER
;
;	LDX     #0
;
	STX     DTIMER
	STX     DTIMER+1
	JSR     INITPALS	;PUT UP STANDARD COLORS
	JSR     CLEARTUN	;CLEAR OUT ALL TUNES
	JSR     NULLOBJS	;NULL OUT ALL OBJECTS.
	JSR     WAITLOAD	;WAIT FOR LOADER TO UPDATE
	JSR     INITDMA		;BUILD DLLS FOR MARIA2
				; AND STARTS DMA DURING VBLANK
				;FALL THROUGH INTO....
* PROGRAM DRIVER: NEEDED TO HANDLE THE VARIOUS PROGRAM STATES.
DRIVER:
	LDA     FRMCNT		;INSURE THAT FRMCNT IS EVEN HERE
	AND     #$FE
	STA     FRMCNT

	LDA     GAMSTATE	; FRAME COUNT AIN'T INC'ED DURING HSC
	CMP     #HSCST
	BEQ     PASTINCF

FRAMSYNC:
	LDA     FRMCNT		;MAKE SURE AT LEAST ONE FRAME HAS
	SEC			; GONE BY SINCE LAST FRAME SYNCH.
	SBC     LASTFRMC
	CMP     #2
	BCC     FRAMSYNC
	LDA     FRMCNT
	STA     LASTFRMC	;UPDATE LAST FRAME COUNT

PASTINCF:
	INC     DTIMER+1	;INCREMENT THE TWO BYTE TIMER
	BNE     ZZNOINC9
	INC     DTIMER
ZZNOINC9:
	JSR     CKJOY		;GET FRESH JOYSTICK INPUTS.
	JSR     CKBUTS		;GET FRESH BUTTON INPUTS (DEBOUNCED).
	JSR     TWINKLE		;TWINKLE STARS ETC.

	LDA     GAMSTATE	;CHECK GAME STATE
	CMP     #PLAYST		;GAMEPLAY STATE
	BEQ     PLAYD
	CMP     #AUTOST		;AUTO PLAY STATE
	BEQ     AUTOD
	CMP     #MENUST		;MENU STATE
	BEQ     MENUD
	CMP     #TITLEST	;TITLE STATE
	BEQ     TITLED
	CMP     #HSCST		;HIGH SCORE CART STATE
	BEQ     HSCD

	BNE     DRIVER		;SAFETY TO PREVENT GOING ASTRAY
				;NOT NEEDED IF WORKS PROPERLY SINCE
				;MUST BE IN ONE OF THE ABOVE STATES.

** DRIVER DISPACHER ROUTINES. **

** TITLE PAGE STATE DISPACHER - HANDLES TIMING DURING TITLE PAGE. **
TITLED:
	LDA     FIREBUT2
	BMI     HESDEAD
	LDX     #$FF
	STX     TURKEY
	DEX
	STX     CHICKEN
HESDEAD:
	LDA     SWCHBITS
	AND     #$08
	BEQ     JIM
	LDA     SWCHA
	ORA     CHICKEN
	AND     TURKEY
	STA     TURKEY
	SEC
	ROL     CHICKEN
	CMP     #$F0
	BNE     JIM
	JMP     GO4IT
JIM:

	LDA     DTIMER	       ;CHECK TIMER
;
;	CMP     #TITLEONT	    ;TIME TO TURN TITLE ON?
;
	BNE     ZCKTOFF
	JSR     ONTITLE	      ;YES
	JSR     CLSCORE	      ;TAKE OFF THE SCORES
ZSEEJOY:
	JSR     SEEJOY
	BCC     DRIVER	       ;BCC = JMP

ZCKTOFF:
	CMP     #TITLEOFT
	BNE     ZSEEJOY
	JMP     DOHSC	        ;FROM TITLE TO HSC

** AUTO STATE DISPACHER. **
AUTOD:
	LDA     DTIMER
	CMP     #AUTOOFFT	    ;DONE WITH AUTO PLAY YET?
	BNE     AUTOGO
MENUTOUT:
	JMP     DOTITLE	      ;COME HERE AFTER AUTO OR MENU TIME OUT
AUTOGO:
	JSR     GAMELOOP
	JSR     SEEJOY
	JMP     DRIVER


** HIGH SCORE CART DISPATCHER.
HSCD:
	JSR     HSCSHOW		;PUT UP ONE TABLE
	LDX     TEMP	        ;ADVANCE TO NEXT ENTRY
	INX
	CPX     #12		;12 ENTRIES
	BCS     OVERHSC
	STX     TEMP
	TAX		        ;TEST AC BITS:
	BNE     HSCD	         ; IF AC NON-ZERO, THEN TRY AGAIN
	JSR     SEEJOY	       ;CHECK FOR USER ACTIONS.
	JMP     DRIVER

OVERHSC:
	JMP     DOAUTO	       ;FROM HSC TO AUTOPLAY


** PLAY STATE DISPATCHER. **

PLAYD:
	JSR     GAMELOOP	     ;DO ONE TIME THRU GAME PLAY

	JSR     SEEPAUZ	      ;CHANGE TO PAUSE IF PAUSE BUT. HIT
	JSR     SEEBUTS
	JMP     DRIVER


** MENU STATE DISPATCHER. **
MENUD:
	LDA     DTIMER
	CMP     #MENUOFFT
	BEQ     MENUTOUT	     ;MENU TIMED OUT

	JSR     SELCHK	       ;READ SELECT INPUT, SET MODES

	JSR     ONTITLE	      ;PUT UP THE LOGO

	;PUT UP DIFFICULTY LEVEL ICON
	LDX     #10
	TXA
	CLC
	ADC     DIFF
	TAY
	JSR     DOICON

	;PUT UP MODE ICON
	LDX     #11
	LDA     #15
	CLC
	ADC     MODE
	TAY
	JSR     DOICON

	;PUT UP SCORES
	JSR     DOSCORE

	;NULL OUT BOTH SHIP ICONS
	LDA     #$FF
	STA     STATUS+12
	STA     STATUS+13
	;PUT UP SHIP ICONS
	LDX     #12
	LDY     #22
	LDA     MODE
	BMI     MENU1PL	      ;ONE PLAYER
	INY
	LDA     MODE
	BEQ     MENU2PL	      ;TWO PLAYER INDIVIDUAL
	CMP     #2
	BNE     MENUTEAM
MENUCOMP:
	INY		        ;TWO PLAYER COMPETITION
	INY
MENUTEAM:
	INY		        ;TWO PLAYER TEAM PLAY
	INY
MENU2PL:
	JSR     DOICON
	INY
	INX
MENU1PL:
	JSR     DOICON

	;CHECK FOR START GAME BUTTONS
	;CAN'T USE SEEJOY HERE; DON'T WANT TO DO DOMENU, ETC.
	LDA     INPT4
	BPL     ZDOPLAYS	     ;JOYSTICK BUTTON HIT
	LDA     INPT4A
	BMI     ZDOPLAYS
	LDA     SWCHBITS
	LSR
	BCS     ZDOPLAYS	     ;RESET  BUTTON HIT
	JMP     DRIVER	       ;NOTHING HIT: CONTINUE
ZDOPLAYS:
	JMP     DOPLAY


***************************************
** ROUTINES USED BY THE DISPATCHERS. **
***************************************

* ROUTINE TO PUT TITLE ON
ONTITLE:
	LDX     #9		 ;PUT UP THE FIRST 10 ICONS
	LDY     #9
TITLELOP:
	JSR     DOICON	       ;PUT UP ICON Y IN SLOT X
	DEY
	DEX
	BPL     TITLELOP

	LDA     #$0E	         ;CHANGE COLOR FOR NAME
	STA     SOFTCOLR+9
	LDA     #$07
	STA     SOFTCOLR+11
;         LDA     #$75	         ;BACKGROUND BARS WILL BE CYCLED
;         STA     SOFTCOLR+10

	RTS

** MENU SELECT ROUTINES **

* CHECK THE PAUSE BUTTON: HANG OUT HERE IF PRESSED, AND PERFORM PAUSE STUFF
SEEPAUZ:
	LDA     SWCHBITS	     ;CHECK PAUSE BUTTON
	AND     #$08
	BEQ     PAUZRTS

	;WE NOW PAUSE FOR STATION IDENTIFICATION...
DOPAUZ:
	LDA     #PAUZST	      ;SHUT OFF TUNER ETC.
	STA     GAMSTATE
	LDA     #0
	STA     AUDV0
	STA     AUDV1
	STA     DTIMER	       ;RESET TIMER FOR VIDEO OUT
	STA     DTIMER+1

PAUZLOOP:
	BIT     MSTAT	        ;SYNCH
	BMI     PAUZLOOP	     ; WAIT 'TILL ON SCREEN
;         BIT     MSTAT	        ; PROTECT AGAINST FLAKEY MSTAT
;         BMI     PAUZLOOP
ZPOSLOOP:
	BIT     MSTAT
	BPL     ZPOSLOOP	     ; WAIT 'TILL OFF SCREEN (IN VBLANK)
;         BIT     MSTAT
;         BPL     ZPOSLOOP

	INC     DTIMER+1	     ;BUMP TIMER
	BNE     ZZNOINC7
	INC     DTIMER
	BMI     VIDOFF	       ;TURN VIDEO OFF WHEN CLOCK ROLLS AROUND
ZZNOINC7:
	JSR     CKBUTS	       ;CHECK PAUSE BUTTON
	AND     #$08
	BEQ     PAUZCKJY

	;PAUSE MODE IS OVER
	LDA     #PLAYST
	STA     GAMSTATE	     ;RESTORE TUNER

	LDA     #$40	         ;TURN ON DMA
	STA     CTRL

PAUZRTS:
	RTS

PAUZCKJY:
	LDA     SWCHA
	EOR     #$FF
	BNE     VIDON	        ;TURN VIDEO ON WHEN JOYSTICK OR
	LDA     INPT4	        ; EITHER PLAYER'S BUTTONS ARE HIT.
	AND     INPT5	        ; (AND HI BITS, ACTIVE LO)
	BPL     VIDON
	JSR     SEEBUTS	      ;CHECK FOR SELECT & RESET
	BCC     PAUZLOOP	     ;BCC = JMP


VIDOFF:
	LDA     #$60	         ; 60 = STOP DMA
	BNE     VIDSTOR	      ; BNE = JMP

VIDON:
	LDA     #$40	         ; 40 = START DMA
VIDSTOR:
	STA     CTRL
	BNE     DOPAUZ	       ; BNE = JMP

* CHECK BUTTONS (PAUSE, RESET, SELECT) SAVING STATE FOR DEBOUNCING.
*         SETS ONES IN EACH BIT OF SWCHBITS ON POSITIVE TRANSITIONS.
CKBUTS:
	LDX     SWCHB
	TXA
	EOR     SWCHBVAL	     ;GET ALL BITS WHICH HAVE CHANGED
	AND     SWCHBVAL
	STA     SWCHBITS	     ;SAVE OLD VALUES OF CHANGED BITS
	STX     SWCHBVAL	     ;SAVE NEW VALUES OF ALL BITS
	RTS

* CHECK JOYSTICK/BUTTONS ETC. FOR CHANGE OF STATE
SEEJOY:
	LDA     STARTBUT	     ;CHECK FIRE BUTTON, NOT SET IN AUTOST
				 ;NEEDED TO PREVENT GOING FROM AUTOST
	BPL     DOPLAY
	LDA     SWCHA	        ;CHECK JOYSTICK MOTION
	AND     #$F0
	EOR     #$F0
	BNE     DOMENU
SEEBUTS:
	LDA     SWCHBITS	     ;CHECK SELECT AND RESET BUTTONS
	LSR
	BCS     DOPLAY
	LSR
	BCS     DOMENU
	RTS

	;ENTER HSC STATE
DOHSC:
	LDA     #0		 ;LOWEST GAME OPTION FOR HSC
	STA     TEMP

	LDA     #HSCST
	JMP     NEWDRVR

	;ENTER MENU STATE
DOMENU:
	LDA     #SELDLY	      ;DEBOUNCE SELECTER
	STA     SELCNT

	LDA     #0		 ;CLEAR MENLEFT
	STA     MENLEFT
	STA     MENLEFT2
	STA     MENLEFTC

	LDA     #MENUST	      ;JUMP INTO MENU STATE
	JMP     NEWDRVR

	;ENTER PLAY STATE
DOPLAY:
	JSR     INITSCOR
	JSR     INITPLAY
	JSR     DOSCORE

	LDA     #PLAYST	      ;GOTO PLAY STATE NOW
	JMP     NEWDRVR

	;ENTER TITLE PAGE STATE
DOTITLE:
	LDA     #TITLEST
	JMP     NEWDRVR

	;ENTER AUTOPLAY STATE
DOAUTO:
	LDA     #0		 ;CLEAR MENLEFT
	STA     MENLEFT
	STA     MENLEFT2
	STA     MENLEFTC

	JSR     DOSCORE

	JSR     INITPLAY	     ;INITIALIZE FOR GAMEPLAY
	LDA     #AUTOST	      ;BUT ITS AUTOPLAY
	JMP     NEWDRVR

SELCHK:
	LDA     SWCHA	        ;P1 JSTICK
	AND     #$F0
	EOR     #$F0
	BNE     SELJOY
	LDA     SWCHB	        ;SELECT BUTTON
	AND     #$02
	BEQ     SELBUT
	LDA     #0
	STA     SELCNT
	RTS

SELBUT:
	DEC     SELCNT
	BPL     SELRTS
	LDX     #SELDLY
	STX     SELCNT

	JSR     INCDIFF
	BNE     SELRTS	       ;INC WORKED OK
	LDA     #MINDIFF	     ;INC HAD NO EFFECT, WRAP AROUND
	STA     DIFF
	JSR     INCMODE
	BNE     SELRTS	       ;INC WORKED OK
	LDA     #MINMODE
	STA     MODE
	BNE     SELCHNG	      ;MINMODE = $FF HERE, SO BNE = JMP

SELJOY:
	DEC     SELCNT
	BPL     SELRTS
	LDX     #SELDLY
	STX     SELCNT

	ASL
	BCS     INCDIFF
	ASL
	BCS     DECDIFF
	ASL
	BCS     DECMODE
* FALL THROUGH TO...
INCMODE:
	LDX     MODE	         ;INCREMENT GAMEPLAY MODE
	CPX     #1		 ;HACK: WE STOP AT 1
	BEQ     SELRTS
	INX		        ;BIGGER HACK: PUSH X INTO RANGE.
	LDA     ZHACKMOD+2,X	 ;BIGGEST HACK: TABLE LOOKUP NEXT MODE.
	STA     MODE
	BPL     SELCHNG

INCDIFF:
	LDA     DIFF	         ;INCREMENT INITIAL GAME DIFFICULTY
	CMP     #MAXDIFF
	BEQ     SELRTS
	INC     DIFF
	BPL     SELCHNG

DECDIFF:
	LDA     DIFF	         ;DECREMENT DIFFICULTY
	CMP     #MINDIFF
	BEQ     SELRTS
	DEC     DIFF
	BPL     SELCHNG

DECMODE:
	LDX     MODE		;DECREMENT MODE
	CPX     #MINMODE
	BEQ     SELRTS
	LDA     ZHACKMOD,X
	STA     MODE

SELCHNG:
	LDA     #0		;HOLD DRIVER CLOCK AT ZERO
	STA     DTIMER
	STA     DTIMER+1
*
	JSR     HSCSUCK		;SUCK IN A NEW HIGH SCORE FOR THIS LVL
	LDA     #17		;JUST TO KNOCK OFF THE 'EQ' BIT
SELRTS:
	RTS

ZHACKMOD:
	.DC.B	$FF,2,0,2,17,1         ;TABLE OF "NEXT MODES" TO KLUDGE IN.

GO4IT:
	LDX     #8
	LDY     #LARGE+$80
ZSNARD:
	STY     STATUS,X
	LDA     PALTAB,X
	STA     PALS,X
	LDA     ELBOUND+2
	STA     ACYC,X
	DEX
	BPL     ZSNARD
STAY4IT:
	LDA     FRMCNT
	AND     #$03	         ;EVERY 4
	BNE     ZEATME
	LDA     FRMCNT
	PHA
	LSR
	STA     FRMCNT
	JSR     EXPLODE
	PLA
	STA     FRMCNT
ZEATME:
	JSR     WAITLOAD
	LDA     #114
	STA     YPOSH+9
	LDA     #BEAG&255
	STA     ACYC+9
	LDA     #$4A
	STA     PALS+9
	JSR     LOGOBARS
	JSR     CKJOY
	JSR     CKBUTS
	JSR     SEEJOY
	BCC     STAY4IT	      ;BCC = JMP


* NMI HANDLER: HANDLES NMI'S GENERATED EACH FRAME BY MARIA AT END OF VISIBLE.
NMI:
	PHA		        ;SAVE STATE
	TXA
	PHA
	TYA
	PHA

	CLD

	LDA     NMICTRL	      ;SEE IF WE ARE DOING HISCORE CART LOGO
	BEQ     NMIHNDL	      ; NO.  DO NORMAL HANDLER
	bne	NMIOVER		;br always  1-Sept-88 *** Dave ***
*	STA     CTRL	         ; YES. SET READ MODE BITS OF CTRL
	EOR     #$03	         ;      INVERT THE BITS
	STA     NMICTRL
	AND     #$03	         ;      IF <> 0 (ENTERING VBLANK)
	BNE     NMIINCFR	     ;        BUMP FRAME COUNT
	JSR     HSCSETRS	     ;SET UP HSC REGISTERS (REFRESH COLORS)
	JMP     NMIOVER

NMIHNDL:
	LDA     FRMCNT
	LSR
	BCC     NOLOAD	       ;EVERY OTHER FRAME, DON'T CALL LOADER
	JSR     LOADER
NOLOAD:
	JSR     TUNER	        ;DO TUNES
NMIINCFR:
	INC     FRMCNT	       ;BUMP FRAME COUNT
	JSR     REFRESH	      ;REFRESH OUR COLORS

NMIOVER:
	PLA		        ;RESTORE STATE
	TAY
	PLA
	TAX
	PLA
IRQ:
	RTI		        ;VECTOR IRQ'S TO THIS LABEL