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Cosmic Defender.asm
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*******************
* COSMIC DEFENDER *
* BY *
* PHILLIP ROEY *
*******************
;
; OPERATING SYSTEM EQUATES
;
AUDCTL = $D208
SKCTL = $D20F
AUDF1 = $D200
AUDC1 = $D201
AUDF2 = $D202
AUDC2 = $D203
AUDF3 = $D204
AUDC3 = $D205
AUDF4 = $D206
AUDC4 = $D207
ATRACT = $4D
VERTI = $0200
DMACTL = $022F
DLST = $0230
GRACTL = $D01D
GPRIOR = $026F
PMBASE = $D407
COLPM0 = 704
COLPM1 = 705
HCOLPM0 = $D012
HCOLPM1 = $D013
HCOLPM2 = $D014
HCOLPM3 = $D015
COLP0 = 708
COLP1 = 709
COLP2 = 710
COLP3 = 711
COLBK = 712
HCOLP0 = $D016
HCOLP1 = $D017
HCOLP3 = $D019
CONSOL = $D01F
KEY = $02FC
HPOSP0 = $D000
STICK = $D300
TRIG0 = $D010
TIMER3 = $021C
TIMER4 = $021E
TIMER5 = $0220
TIMERF3 = $022A
TIMERF4 = $022C
TIMERF5 = $022E
NMIEN = $D40E
SETVBV = $E45C
XITVBV = $E462
SIOINI = $E465
HSCROL = $D404
WSYNC = $D40A
CHBAS = 756
SIZEM = $D00C
M0PF = $D000
M0PL = $D008
P0PF = $D004
P0PL = $D00C
HITCLR = $D01E
CHORG = $E000
RANDOM = $D20A
;
; PAGE ZERO EQUATES
;
*= $80
;
KILLU .DS 1 COLLISION
KILLIT .DS 1 FLAGS
KILLPL .DS 1 DITTO
OVER .DS 1 GAMEOVER?
FRAME .DS 1 COUNTER
PAUSE .DS 1 PAUSE FLAG
SNDF1 .DS 1 MISSLE SND
SND1 .DS 1 LOCATIONS
OXM0 .DS 1 MISSLE X
OYM0 .DS 1 MISSLE Y
XPY .DS 1 EXPLOSION Y
XPIMAGE .DS 1 EXP. IMAGE#
EXPTIME .DS 1 EXP. TIMER
TEMPLO .DS 1
TEMPHI .DS 1
SCRTEMP .DS 1
EXPLODE .DS 1 EXP. SOUND CNTR
TEMP .DS 1
TEMP2 .DS 1
NONEW1 .DS 1 SCROLL FLAG
XPLON .DS 1 EXP. FLAG
ABX .DS 1 SCREEN POS. LSB
ABY .DS 1 SCREEN POS. MSB
FX .DS 1
FY .DS 1
OX .DS 1 PLAYER X
OY .DS 1 PLAYER Y
MSL0 .DS 1 MISSLE FLG
CSHIFT .DS 1 DLI COLOR
DSHIFT .DS 1 SHIFT USE
TITLF .DS 1 TITLE SCRN FLAG
ROCKSPD .DS 11
ROCKPOS .DS 11 NASTY X LOC
RIMAGE .DS 11
COLOR2 .DS 11 COLORS OF
COLOR3 .DS 11 NASTIES
ADR .DS 2
DLINE .DS 1 NASTY COUNTER
;
; MISCELLANEOUS EQUATES
;
;
SCRN = $3000 SCREEN MEM.
PLAYER = $00 PMG MEMORY
;
*= $2000 ORIGIN
;
; INITIALIZATION OF GAME
;
START CLD
LDY # <MAIN POINT TO
LDX # >MAIN VBI ROUTINE
LDA #7
JSR SETVBV
LDA #$3E ENABLE PMG
STA DMACTL
LDA #$03
STA GRACTL
LDA #34
STA GPRIOR
LDA #5 SET MISSLE
STA SIZEM SIZE
LDA #100
STA COLP0 SET
LDA #$26 PLAYFIELD
STA COLP1 AND P/M
LDA #$38 COLORS
STA COLP2
LDA #$D4
STA COLP3
LDA #0
STA COLBK
LDA #170
STA COLPM0
LDA #$36
STA COLPM1
LDA # >PLAYER POINT TO
STA PMBASE P/M AREA
;
; MAKE 3 COPIES OF CHAR SET
;
LDY #0
COPY LDA CHORG,Y
STA PLAYER+$0800,Y
STA PLAYER+$0C00,Y
STA PLAYER+$1000,Y
LDA CHORG+256,Y
STA PLAYER+$0900,Y
STA PLAYER+$0D00,Y
STA PLAYER+$1100,Y
DEY
BNE COPY
;
; INSTALL CUSTOM CHARACTERS
;
LDY #119
INST LDA CHSET,Y
STA PLAYER+$0808,Y
LDA CHSET2,Y
STA PLAYER+$0C08,Y
LDA CHSET3,Y
STA PLAYER+$1008,Y
DEY
BPL INST
LDA # >PLAYER+$0800 POINT TO
STA CHBAS NEW CHAR. SET
;
; EACH NEW GAME STARTS HERE
;
BEGIN JSR PLRINT CLEAR P/M
JSR SNDINT KILL SOUND
JSR CLRSCRN CLR SCREEN
JSR VARINT INITIALIZE VARIABLES
JSR TITLE DISPLAY TITLES
JSR GRID ADD FFIELDS
JSR ROCKS AND ROCKS
JSR ROCKINT AND NASTIES
;
; MAIN GAME LOOP
;
MLOOP JSR COLDET CHECK FOR COLLISIONS
LDA CONSOL ABORT GAME?
CMP #3 (OPTION)
BNE MLOOP NO,LOOP
BEQ BEGIN YES,RESTART
;
; INITIALIZE SOUND CHANNELS
;
SNDINT JSR SIOINI
LDA #0
STA EXPLODE
LDY #7
STA AUDCTL
SN1 STA AUDF1,Y
DEY
BPL SN1
RTS
;
; ADD ROCKS TO SCREEN
;
ROCKS LDA LEVEL GET NUMBER
SEC OF ROCKS,
SBC #17 AND PUT IN
TAY X REG
LDA #0
STA ADR
LDA NUMROCK,Y
STA TEMP AND TEMP
TAX
R1 LDA RANDOM GET A VALID
CMP #250 RANDOM
BCS R1 LOCATION
TAY
R2 LDA RANDOM
AND #$3E
CMP #40
BCS R2
ADC #1 CHECK IF IT
JSR EMPTY IS EMPTY
BNE R1 NEXT!
LDX TEMP GET # OF ROCKS FOR
R3 LDA RANDOM 2ND PAGE OF SCRN MEM
CMP #48 GET A VALID
BCC R3 LOCATION
CMP #255
BEQ R3
TAY
R4 LDA RANDOM
AND #$3E
CMP #40
BCS R4
JSR EMPTY LOOK FOR AN EMPTY SEAT.
BNE R3 NEXT!
RTS
;
EMPTY CLC CHECK TO MAKE
ADC # >SCRN SURE THE SPACE
STA ADR+1 FOR ALL FOUR
LDA (ADR),Y PARTS IS VACANT
INY
ORA (ADR),Y
INC ADR+1
INC ADR+1
ORA (ADR),Y
DEY
ORA (ADR),Y
BNE RX NO VACANCY! EXIT
DEC ADR+1 POKE 4
DEC ADR+1 PART ROCK
LDA #1 INTO
STA (ADR),Y SCREEN
LDA #2 MEMORY
INY IN LIVING
STA (ADR),Y COLOR...
INC ADR+1
INC ADR+1
LDA #4
STA (ADR),Y
LDA #3
DEY
STA (ADR),Y
LDA # >SCRN
STA ADR+1
DEX DEC COUNTER
RX RTS
;
NUMROCK .BYTE 40,60,70,100,125,70,100,80,100
;
; CHECK FOR COLLISIONS
;
COLDET LDA M0PF HAS MISSLE HIT?
BEQ C1 NO,CONT...
STA KILLIT YES,SET FLG
C1 LDA M0PL HIT NASTY?
AND #$FC
BEQ C2 NO,CONT...
STA KILLPL YES,SET FLG
C2 LDA P0PF HIT WALL OR ROCK?
BNE DIE YES,SET FLAG
LDA P0PL DID WE RUN
AND #$FD INTO NASTY?
BEQ NODIE NO. EXIT
DIE STA KILLU
STA HITCLR
NODIE RTS
;
; CLEAR OUT SCROLLING PORTION OF SCREEN
;
CLRSCRN LDA #42+>SCRN 21 LINES *
STA ADR+1 2 PAGES + SCRN ADDR
LDX #0
STX ADR
LDY #0
CL1 TXA LOOP UNTIL
STA (ADR),Y WE'VE GOT
INY LOTS OF
BNE CL1 NOTHING
DEC ADR+1
LDA # >SCRN-1
CMP ADR+1
BNE CL1
RTS
;
; ZERO OUT P/M MEMORY
;
PLRINT LDA #0
TAY
PL1 STA PLAYER+$0300,Y
STA PLAYER+$0400,Y
STA PLAYER+$0500,Y
STA PLAYER+$0600,Y
STA PLAYER+$0700,Y
INY
BNE PL1
RTS
;
; REINITIALIZE GAME VARIABLES
;
VARINT LDA #0
STA PAUSE
STA KILLU
STA KILLIT
STA KILLPL
STA FX
STA FY
STA XPY
STA XPIMAGE
STA ABX
STA NONEW1
LDA # >SCRN
STA ABY
LDA #19
STA LIVES
STA OVER
LDA #$54 LOAD MEMORY SCAN
STA ML2
STA HITCLR
LDA #50
STA OX
LDA #100
STA OY
STA FRAME
RTS
;
; PLAYER BUYS CEMENT OVERSHOES
;
BITEIT LDA XPLON ALREADY BITING IT?
BNE BT1 YES,CONT...
STA SND1 KILL SOUND
STA XPIMAGE
STA HPOSP0+1 EXPLOSION
LDA #1 SET DEATH
STA XPLON FLAG
JSR SNDINT KILL REST OF SOUND
JSR MISEND AND MISSLE
LDA #100 SET TIMER
STA FRAME
LDA #20
STA AUDCTL MAKE DEATH
LDA #200 TYPE NOISES
STA AUDF4
LDA #135
STA AUDC3
STA AUDC4
BT1 LDA RANDOM FLASH
AND #6 SHIP
STA HCOLPM0 IN A NICE
STA HCOLPM1 GREY
LDA RANDOM PALLOR.
STA AUDF1 MORE NOISE
LDA RANDOM
STA AUDF2
LDA RANDOM
AND #$DF
STA AUDC1
STA AUDC2
DEC FRAME DONE KILLING?
BNE DEDEND NO.
JSR SNDINT KILL NOISE
LDA #50 REST SHIP
STA OX LOCATION
STA HITCLR
LDA #100
STA OY
LDA #0
STA XPLON CLEAR FLAGS
STA KILLU
DEC LIVES ZAP A LIFE
LDA LIVES ANY LEFT?
CMP #16
BEQ GMOVER NO? THE BIG SLEEP!
LDA #0 YES,RESET
STA ABX TO START
LDA # >SCRN OF SCREEN
STA ABY
STA HITCLR
JSR SCREEN CLEAN UP
JSR PLRINT SCREEN AND
JSR ROCKINT NASTIES
DEDEND JMP XITVBV
;
GMOVER JSR PLRINT CLEAN UP
JSR SNDINT SCREEN +
LDA #0 SOUND
STA KILLU AND
LDA #1 SET GAME
STA HITCLR OVER
STA OVER FLAG
LDA # <BLANK PUT GAME
STA ML1+1 OVER
STA ML3+1 INTO THE
LDA # >BLANK MIDDLE OF
STA ML1+2 THE SCREEN
STA ML3+2
LDA # <MESSAGE
STA ML2+1
LDA # >MESSAGE
STA ML2+2
LDA #$46
STA ML2
LDA #255
STA TIMERF5 HANG
STA TIMER5 AROUND
GM1 LDA TIMERF5 AWHILE
BNE GM1 THEN
JMP BEGIN ALL OVER
;
; VERTICAL BLANK INTERRUPT
; THIS IS WHERE ALL THE ACTION IS!
;
MAIN LDA #0
STA DLINE POINT TO
LDA OVER IS GAME ASLEEP?
BNE ENDVB YES,BYE...
STA ATRACT NO ATTRACT MODE
LDA KILLPL HIT NASTY?
BEQ MA2 NO,CONT..
JSR XPINIT YES,KILL
JSR KILLPLR IT
MA2 LDA KILLU HIT US?
BEQ MA1 NO,CONT...
JMP BITEIT YES,SUICIDE
MA1 LDA KEY SPACEBAR
CMP #$21 PRESSED
BNE NOKEY NO,BYE
LDA #255 YES TOGGLE
STA KEY PAUSE
LDA PAUSE FLAG
EOR #255
STA PAUSE
NOKEY LDA PAUSE FLAG SET?
BNE ENDVB YES,BYE...
JSR ANIMATE ROTATE CHAR SETS
JSR ATTACK MOVE NASTYS
JSR RSTICK READ JOYSTICK
JSR MOVE MOVE SHIP
JSR MISL AND MISSLES
JSR SOUND BOOM
JSR XPLODE FIREWORKS
JSR SCROLL SCROLL SCREEN
JSR SCREEN UPDATE DISP. LIST
ENDVB LDA TITLF TITLES?
BEQ EN1 NO,BYE...
LDA # <TDLI
STA VERTI
LDA # >TDLI
STA VERTI+1
EN1 JMP XITVBV
;
; READ JOYSTICK
;
RSTICK LDA STICK GET STICK
LDX OY CHECK STICK FOR
LSR A MOVEMENT IN A
BCS RS1 DIRECTION AND
CPX #32 CHECK IF WE ARE
BEQ RS1 AT OUR LIMITS IN
DEC OY THAT DIRECTION
RS1 LSR A
BCS RS2
CPX #190
BEQ RS2
INC OY
RS2 LDX OX
LSR A
BCS RS3
CPX #50
BEQ RS3
DEC OX
RS3 LSR A
BCS RS4
CPX #100
BEQ RS4
INC OX
RS4 RTS
;
; MOVE PLAYER0 AND MISSLE1 (YOUR SHIP)
;
MOVE LDX OX
STX HPOSP0
INX
INX
STX HPOSP0+5
LDY OY
LDX #8
MO0 LDA SHAPE,X
STA PLAYER+$0400,Y
LDA PLAYER+$0300,Y
AND #$F3
STA PLAYER+$0300,Y
INY
DEX
BPL MO0
LDY OY
LDA PLAYER+$0303,Y
ORA #$0C
STA PLAYER+$0303,Y
LDA PLAYER+$0304,Y
ORA #$04
STA PLAYER+$0304,Y
LDA PLAYER+$0305,Y
ORA #$0C
STA PLAYER+$0305,Y
RTS
;
; SHIP SHAPE (ARGH!)
;
SHAPE .BYTE 0,$C0,$70,0,$73,0,$70,$C0,0
;
; MOVE MISSLE AND MISSLE SOUND
;
MISL LDA MSL0 ACTIVE?
BNE MSMOV YES,MOVE IT
LDA TRIG0 TRIGGER PRESSED?
BNE MSLEND NO,BYE...
LDA #1 SET FLAG
STA MSL0
LDY OY GET Y COORD
LDA #3 PUT MISSLE ON SCREEN
STA PLAYER+$0304,Y
STY OYM0 STORE Y
LDA #$25 INITIALIZE
STA AUDC1 MISSLE
LDA #50 SOUND
STA SNDF1
LDA OX CALCULATE
ADC #6 INITIAL X
STA OXM0 COORD
MSMOV INC OXM0 MOVE MISSLE
INC OXM0 RIGHT
LDA OXM0
STA HPOSP0+4
INC SNDF1 DECREASE
INC SNDF1 FREQUENCY
LDA SNDF1
STA AUDF1
LDA #205 MISSLE AT EDGE?
CMP OXM0
BCC MISEND YES,KILL MISSLE
LDA KILLIT DID MISSLE HIT?
BEQ MSLEND NO,BYE...
JSR LOCATE YES,BUT WHAT&WHERE
JSR ERASE ZAP IT
MISEND LDA #0 MISSLE DEAD
STA AUDC1 SO KILL SOUND
STA MSL0 CLEAR FLAG
STA KILLIT
LDY OYM0 ERASE MISSLE
LDA PLAYER+$0304,Y
AND #$FC
STA PLAYER+$0304,Y
MSLEND RTS
;
; SCROLL SCREEN
;
SCROLL LDA TIMERF3 TIME YET?
ORA NONEW1 OR AT END OF LEVEL?
BNE M2 THEN DON'T SCROLL
LDA LEVEL GET SCROLL
SEC SPEED
SBC #17 AND DROP
TAY IT IN TIMER
LDA SPEED,Y 3 AND RESET
STA TIMER3 FLAG
STA TIMERF3
LDY FX SCROLLED WHOLE
DEY CHARACTER?
BPL M15 NO,CONT...
INC ABX YES, UPDATE SCREEN ADD.
BNE M14 WHOLE PAGE DONE?
INC ABY YES, BUMP SCREEN PAGE
M14 LDY #3 RESET
M15 STY FX SCROLL CNTR
M2 LDX FX
STX HSCROL
RTS
;
; UPDATE SCREEN MEMORY IN DL
;
SCREEN LDY # >SCRN+$0200 ARE WE AT
LDA ABY THE END OF
CPY ABY 2ND PAGE OF SCREEN?
BNE S11 NO,CONT..
DEC NONEW1 YES,DELAY TILL NEW LEVEL
BNE SXIT BYE...
JSR LEVELUP SET UP NEW LEVEL
LDA # >SCRN RESET TO SCRN START
S11 PHA
LDX #20 # OF LINES TO BE SCROLLED
LDY #6 OFFSET IN DL
S0 LDA ABX GET LSB AND
STA DSP,Y STORE IN DL
INY
PLA GET MSB AND
STA DSP,Y STORE IN DL
CLC ADD TWO
ADC #2 PAGES
PHA AND HIDE IT ON STACK TILL NEXT
INY LOOP
INY INC DL POINTER
DEX DONE?
BPL S0 NO,LOOP..
PLA YES, CLEAR STACK
SXIT RTS
;
SPEED .BYTE 3,3,2,2,2,2,2,1,1
;
; SCORE ROUTINE:ENTRY CONDITION
; XREG: SCORE DIGIT TO CHANGE
; YREG: AMOUNT TO ADD TO DIGIT
;
SCOREIT INC SCORE,X GET DIGIT
LDA SCORE,X AND BUMP IT
CMP #26 DIGIT>9?
BEQ BIGSCR YES. FIX IT
SCR DEY NO. ARE WE
BEQ SCREND DONE? YES.
BNE SCOREIT NO. LOOP
BIGSCR LDA #16 DIGIT=0
STA SCORE,X STORE IT
STA SCRTEMP SCORE CARRY FLAG
BNE SCR LOOP...
;
SCREND LDA SCRTEMP FLAG SET?
BEQ SC1 NO.
TXA LAST DIGIT?
BEQ SC1 YES.
DEX SET XREG
LDY #1 AND YREG
LDA #0 CLEAR FLAG
STA SCRTEMP AND START
BEQ SCOREIT ALL OVER
SC1 JMP HIGHSC CHECK FOR HIGH SCORE
;
; FIND OUT WHERE WE HIT
;
LOCATE LDA OYM0 GET Y COORD
SEC AND CONVERT
SBC #29 TO IRG4
LSR A SCREEN
LSR A COORDINATES
AND #$FE ADD THE
CLC START OF
ADC DSP+7 SCREEN MEM.
STA TEMPHI SHAKE WELL AND VIOLA! THE MSB
LDA FX GET LSB OF
ASL A SCREEN
CLC ADD THE MISSLES
ADC OXM0 X COORD
SEC CONVERT
SBC #39 TO IRG4
LSR A COORDINATES
LSR A ADD SCROLL
CLC
ADC ABX AND WE GET
STA TEMPLO THE LSB
BCC LOC1 OVER BORDER THEN
INC TEMPHI BUMP MSB
LOC1 RTS
;
; FIND OUT WHAT WE HIT
;
ERASE LDA TEMPLO GET SCREEN
STA ADR MEMORY AND
LDA TEMPHI SEARCH TILL
STA ADR+1 WE FIND A
STA HITCLR NONZERO
LDY #0 CHARACTER
LDA (ADR),Y (A VICTIM!)
BNE GOTIT
INY
LDA (ADR),Y
BNE GOTIT
INY
LDA (ADR),Y
BEQ LOC1
GOTIT CMP #1 IF CHAR IS
BEQ ERASE4 1-4,ITS A
CMP #2 ROCK.
BNE GOT1 SET TO TOP
DEC ADR RIGHT CHAR
JMP ERASE4 OF ROCK,
GOT1 CMP #3 THEN JUMP
BEQ GOT2 TO ERASE4
CMP #4
BNE GOT4
DEC ADR
GOT2 DEC ADR+1
DEC ADR+1
JMP ERASE4
GOT4 CMP #10 GENERATOR?
BNE GOT5 NO,CONT..
LDA #13 YES,KILL IT
STA (ADR),Y SET TO TOP
INC ADR+1 OF FIELD.
INC ADR+1
JMP ERASE2V ERASE IT!
GOT5 CMP #9 LOWER GENERATOR?
BNE LOC1 NO,BYE..
LDA #13 YES,KILL IT
STA (ADR),Y SET TO TOP
DEC ADR+1 OF FORCE
DEC ADR+1 FIELD.
DEC ADR+1
DEC ADR+1
JMP ERASE2V ERASE IT.
;
ERASE4 LDA #0 ERASE THE
STA (ADR),Y FOUR PART
INC ADR+1 ROCK BY
INC ADR+1 STORING A
STA (ADR),Y BLANK IN
INY EACH OF
STA (ADR),Y THE FOUR
DEC ADR+1 FORMER
DEC ADR+1 POSITIONS
STA (ADR),Y
LDX #3 SET SCORE
LDY #5 TO 50 PTS.
BNE ER2
;
ERASE2V LDA #0 STORE A
STA (ADR),Y BLANK CHAR
INC ADR+1 IN THE 2
INC ADR+1 FORCE FIELD
STA (ADR),Y POSITIONS
LDX #2 SET SCORE
LDY #2 TO 200 PTS.
ER2 STA KILLIT CLR COLLISION FLG
JSR SCOREIT
LDA #25 SET BOOM
STA EXPLODE COUNTER
JMP XPINIT FIREWORKS
;
; BOOM!
;
SOUND LDA EXPLODE FLAG SET?
BEQ SNDEND NO,BYE...
LDA TIMERF4 TIME YET?
BNE SNDEND NO,BYE...
DEC EXPLODE SET TO NEXT
LDA EXPLODE TONE+CONTRL
STA TIMERF4 RESET FLAG
BEQ SNDEND ANY LEFT? NO,BYE
TAY YES,GET
LDA EXPSND,Y THE NEXT
STA AUDF2 TONE + CTL
LDA RANDOM AND PUT'EM
ORA #$C0 IN (THE)
STA AUDF3 POKEY
LDA EXPTONE,Y
ORA #$40
STA AUDC2
STA AUDC3
LDA #2
STA TIMER4
SNDEND RTS
;
EXPSND .BYTE $F5,$F4,$F3,$F2,$F2
.BYTE $F0,$F2,$F5,$E9,$E0
.BYTE $EF,$F0,$F1,$F2,$F3
.BYTE $F4,$F5,$F4,$F1,$F5
.BYTE $F2,$F3,$F4,$F5,$F5
EXPTONE .BYTE 0,0,1,2,3,4,5,5,6,6
.BYTE 7,7,8,8,9,9,9,10,10,10
;
; NEXT LEVEL,PLEASE....
;
LEVELUP INC LEVEL BUMP LEVEL
LDA LEVEL LVL>9?
CMP #26
BNE LV2 NO,CONT...
LDA #20 YES,BACK TO
STA LEVEL LEVEL FOUR
LV2 LDA #$40 DISABLE INTERRUPTS
STA NMIEN AND TELL COMPUTER
PHP TO STAY PUT
SEI TILL NOTIFIED!
JSR CLRSCRN CLEAR SCRN
LDA #0 RESET TO
STA ABX SCRN START
STA MSL0 KILL MISSLE
JSR SNDINT AND SOUND
LDA # >SCRN PAGE 1 OF
STA ABY SCREEN
JSR SCREEN UPDATE DL
STA HITCLR CLEAR COLLISIONS
JSR GRID ADD GRIDS
JSR ROCKS AND ROCKS
LDA #0 RESET AND
LDX #10 ADD NASTIES
LV1 STA RIMAGE,X
DEX
BPL LV1
JSR ROCKINT
INC LIVES ADD AN EXTRA LIFE
PLP AND BACK TO
LDA #$C0 THE REAL
STA NMIEN WORLD....
RTS
;
; ROTATE CHARACTER SETS
;
ANIMATE LDA TIMERF5 TIME YET?
BNE AN3
LDA #4 RESET TIMER
STA TIMER5 AND FLAG
STA TIMERF5
LDA CHBAS
CMP # >PLAYER+$1000 3RD SET?
BEQ AN2 OOPS..
CLC NO,ADD 1K
ADC # >1024 TO CHBAS
BNE AN1 JMP ALWAYS
AN2 LDA # >PLAYER+$0800 RESET TO
AN1 STA CHBAS 1ST CHAR
AN3 RTS SET AND BYE
;
; HIGH SCORE?!?!?!
;
HIGHSC LDY #0 CHECK SCORE
HI1 LDA SCORE,Y FROM MS TO
CMP HIGH,Y LS DIGIT
BEQ HI3 EQUAL LOOP
BCC HSCOREND LOWER,CONT
BCS NEWHIGH REPLACE HIGH SCORE
HI3 INY
CPY #4
BNE HI1 LOOP....
NEWHIGH LDY #0 COPY
NH1 LDA SCORE,Y SCORE INTO
STA HIGH,Y HIGH SCORE
INY
CPY #4
BNE NH1 LOOP...
HSCOREND RTS
;
; ADD FORCE FIELD GRIDS
;
GRID LDA LEVEL GET SPACE
SEC BETWEEN
SBC #17 GRIDS FOR LEVEL
TAX
LDA GATES,X AND THROW
STA TEMP IN TEMP
LDY #0 THEN GET
LDA # >SCRN OFFSET AND
STA TEMP2 ADD IT TO
LDA OFFSET,X START OF
STA ADR SCREEN MEM.
GR1 LDA TEMP2 POKE THE
STA ADR+1 3 GRID
LDX #7 CHARACTERS
GR2 LDA #5 INTO
STA (ADR),Y MEMORY
INC ADR+1
INC ADR+1
LDA #6
STA (ADR),Y
INC ADR+1
INC ADR+1
LDA #7
STA (ADR),Y
INC ADR+1
INC ADR+1
DEX
BNE GR2
GR3 LDA RANDOM FIND A
AND #$1F VALID GATE
CMP #20 LOCATION
BCS GR3
CMP #5
BCC GR3
DEC ADR AND ADD THE
ASL A FORCE FIELD
CLC AND
ADC TEMP2 GENERATORS
STA ADR+1
LDA #8
STA (ADR),Y
DEC ADR+1
DEC ADR+1
LDA #9
STA (ADR),Y
DEC ADR+1
DEC ADR+1
LDA #140 FORCEFIELD
STA (ADR),Y
INY
LDA #0
STA (ADR),Y
DEC ADR+1
DEC ADR+1
STA (ADR),Y
DEY
LDA #139 FORCEFIELD
STA (ADR),Y
DEC ADR+1
DEC ADR+1
LDA #10
STA (ADR),Y
DEC ADR+1
DEC ADR+1
LDA #8
STA (ADR),Y
LDA ADR ADD SPACE
ADC TEMP AND SCREEN
STA ADR LOCATION
BCC GR1 BUMP MSB
INC TEMP2 IF
LDA TEMP2 NECESSARY
CMP # >SCRN+$0100 OUT OF ROOM?
BEQ GR1 NO,LOOP..
RTS
;
GATES .BYTE 255,150,60,30,30,60,60,90,70
OFFSET .BYTE 255,200,100,75,50,50,50,200,100
;
; MAIN GAME DLI
;
DLI PHA SAVE XREG
TXA AND A REG
PHA
LDX DLINE INC NASTY
INC DLINE
LDA ROCKPOS,X GET LOCATION
STA HPOSP0+3 AND STORE IN PLR2
STA HPOSP0+2 AND PLR3
LDA COLOR2,X PUT COLOR
STA HCOLPM2 DIRECTLY
LDA COLOR3,X INTO
STA HCOLPM3 HARDWARE REGISTERS
CPX #10 ANY LEFT?
BNE DL1 YES,LOOP..
LDA # <DLI2 NO,POINT
STA VERTI TO NEXT
LDA # >DLI2 DLI
STA VERTI+1
DL1 PLA RESTORE A
TAX AND X
PLA
RTI
;
DLI2 PHA
LDA #$F8 POKE SCORE
STA HCOLP0 COLORS
LDA #$98 DIRECTLY
STA HCOLP1 INTO
LDA #38 HARDWARE
STA HCOLP3 REGISTERS
LDA # <DLI POINT TO
STA VERTI MAIN
LDA # >DLI DLI
STA VERTI+1
PLA
RTI
;
; ATTACTING NASTIES.....
;
ATTACK LDX #0
STX DLINE
AT3 LDA ROCKSPD,X NASTY ACTIVE?
BEQ AT1 NO,GIVE IT LIFE!
LDA ROCKPOS,X YES MOVE
SEC IT
SBC ROCKSPD,X LEFT
BNE AT2 STILL ON SCREEN?
STA ROCKSPD,X NO, RESET POSITION
LDA #254 AND SPEED
AT2 STA ROCKPOS,X