; Defender for the Atari 2600 VCS ; ; Copyright 1982 Atari ; Written by Bob Polaro ; ; Reverse-Engineered by Nick Bensema & Manuel Polik ; ; Compiles with DASM ; ; History ; 24.02.1997 - Initial Release by Nick Bensema ; 18.10.2.1K - Continued by Manuel Polik ; 08.11.2.1K - Radar display finished ; 08.11.2.1K - Update released include vcs.h ; RAM variables: radarColor = $90 ; Color used for P1 in radar bcdGameVariant = $9B ; Current game variant in BCD Format(1-20) frameCounter = $A3 ; is incremented once every frame radar1VerPos = $AA ; vertical position of radar dot radar2VerPos = $AC ; vertical position of radar dot enemyWave = $D2 ; Current wave of enemies gameColors = $E8 ; table of the colors used in the game ; -$EE CITYGFX = $D4 JOYSTICK = $B3 ; Begin source processor 6502 ORG $F000 START: SEI CLD ; Clear all memory LDX #$FF TXS LDA #$00 LF007: STA WSYNC,X DEX BNE LF007 LDX #$FF STX $98 ;Load $98 and bcdGameVariant STX bcdGameVariant ;with #$FF JSR LFD3B JSR LFD1C STA $A2 JSR LFD17 LF01D: JSR LF08C LDA $CB BNE LF037 LDA $B4 BNE LF02E JSR LF0F0 JSR LF1D6 LF02E: JSR LF227 JSR LF2E8 JSR LF33C LF037: JSR LF3EA JSR LF551 JSR LF5FF JSR LF628 JSR LF66E JSR LF45B JSR LF4A2 JMP LF6C7 LF04F: LDA $CB BEQ LF062 INY STY $E6 DEC $CB LDA $CB BNE LF084 JSR LFDC3 JSR LFCE3 LF062: JSR LF8AB JSR LF969 JSR LF9A2 JSR LF9FB JSR LFA4F LDA $91 BNE LF07B JSR LFADD ;These two executed only JSR LFB37 ;if $91 equals zero LF07B: JSR LFB90 JSR LFC0C JSR LFC43 LF084: LDA INTIM BNE LF084 JMP LF01D ; Do vertical blanking LF08C: LDA #$FF STA WSYNC STA VSYNC STA VBLANK STA WSYNC STA WSYNC STA WSYNC STA WSYNC ; Set timer LDA #$36 STA TIM64T LDY #$00 STY PF0 STY VSYNC LDX #$7F STX VBLANK LDY $A2 LDA.wy $00C2,Y STA $C0 ; Display value for $C2 LDA.wy $00C4,Y STA $C1 ; Display value for $C4 ; I keep seeing stuff like this. ; It smells of random number generation. LDA $98 ASL EOR $98 ASL ASL ROL $98 LDA $CB BEQ LF0CD LDA #$00 STA $BD STA $BF JSR LFCAC ; This little routine grabs the appropriate ; joystick readings and shifts them to a common ; location so that it needn't be considered further. LF0CD: LDA SWCHA LDY $A2 ;A2 seems to be player number. AND.wy PLYRJOY,Y ;Y= 0: 0xF0 1: 0x0F STA JOYSTICK ;AND mask for joytick CPY #$01 BNE LF0E1 ASL ASL ASL ASL STA JOYSTICK LF0E1: LDX $8D BNE LF0E7 STX $91 LF0E7: CMP #$F0 BEQ LF0EF LDA #$78 STA $8D LF0EF: RTS LF0F0: JSR LFC7B LDA $CD BMI LF13A ;Skip if less than zero. ;ON $CD goto LF16E, LF149, LF158 CMP #$01 BEQ LF16E CMP #$02 BEQ LF149 CMP #$03 BEQ LF158 LDX $BB ; if ( $80 [ $BB ] & 0xF0 )== 0 LDA $80,X AND #$F0 BNE LRTS1 ; and ( $80 [ $BB ] & 0x0F )== 4 LDA $80,X AND #$0F CMP #$04 BNE LRTS1 ; and radar1VerPos & 0x80 == 0 LDA radar1VerPos BMI LRTS1 ; and $CE & 0x80 == 0 LDA $CE BMI LRTS1 ; and $A8 == $A9 LDA $A8 CMP $A9 BNE LRTS1 ; then $AF = $C6 = $CD = 0xFF LDA #$FF STA $CD STA $C6 STA $AF ; $C7 = (radar2VerPos - 1) * 16 LDA radar2VerPos SEC SBC #$01 ASL ASL ASL ASL STA $C7 ; $CA = $CE ;and if I'm right, $B9 = $BB. LDA $CE STA $CA STX $B9 LF13A: LDA frameCounter AND $93 BNE LRTS1 LDA $C7 CMP #$17 BCC LF166 DEC $C7 LRTS1: RTS LF149: CMP $AF ;Branched here if $CD = 2 BCS LF1B8 ;Branch if radar2VerPos > $AF LDA frameCounter AND #$03 BNE LRTS1 ;RTS if frameCounter has bits 0 or 1. DEC $AF DEC $C7 RTS LF158: LDA $AD ; Branched here if $CD = 3 CMP #$1E BNE LRTS1 ;RTS if $AD != #$1E. STA $8A ;$8A = $AD LDA #$05 STA $99 BNE LF1C9 ; Always branch LF166: INC $AF ;Branched here if $C7 < 0x17 LDA $AF CMP #$0E BCC LRTS1 ;Branch if $AF < $0E LF16E: LDA $C7 ; Branched here if $CD = 1 LDY #$01 STY $CD ; CMP #$87 BCS LF188 LDA frameCounter AND $93 BNE LRTS1 INC $C7 LDA $C7 SEC SBC #$0C STA $AF RTS ;Branch here is $C7 == 0x87 LF188: LDX $B9 LDA #$05 STA $80,X LF18E: LDY $CA LDA $91 BNE LF1C9 LDX $A2 LDA #$31 STA $8A LDA $CF,X ORA LFF12,Y STA $CF,X CMP #$FF BNE LF1C9 STA $CB LDX #$07 LF1A9: LDA $80,X AND #$0F CMP #$04 BNE LF1B3 INC $80,X LF1B3: DEX BPL LF1A9 BMI LF1C9 LF1B8: LDA $BA CMP #$32 BEQ LF18E JSR LFD2F LDA #$05 STA $9A LDA #$02 STA $99 LF1C9: LDA #$64 STA $CA STA $B9 LDA #$00 STA $CD STA $AF RTS LF1D6: JSR LFC7B LDY $B8 LDX LFF06,Y LDA frameCounter AND $93 BNE LF208 LDA $89 BNE LF208 CPY #$05 BEQ LF1F0 CPX #$00 BNE LF208 LF1F0: INC $E3 ;if $AD < $B0 LDA $B0 CMP $AD BCC LF1FC ;then DEC $E3 DEC $E3 LF1FC: INC $E0,X LDA $A5 CMP $A6 BCS LF208 DEC $E0,X DEC $E0,X LF208: INC $E4 LDA frameCounter AND #$07 BNE LRTS2 DEC $C8 DEC $AE DEC $E2 LDA $8B BPL LF21E INC $C8 INC $C8 LF21E: LDA $98 BMI LRTS2 INC $E2 INC $E2 LRTS2: RTS LF227: LDA $91 BEQ LF230 LDA #$01 STA $CC RTS LF230: LDX #$08 LDA $B4 BNE LRTS2 LF236: LDA LFE8E,X CMP JOYSTICK BEQ LF240 DEX BNE LF236 LF240: LDA LFE97,X STA $93 LDA LFEA0,X TAX CMP $CC BEQ LF25F LDA frameCounter AND #$0F BNE LF261 LDA #$FF STA $B5 CPX #$00 BEQ LF25F LDA #$00 STA $E6 LF25F: STX $CC LF261: LDA $CD CMP #$03 BNE LF26F LDA #$82 CMP $AD BCS LF26F STA $AD LF26F: LDA $AD CMP #$19 BNE LF27B LDA frameCounter AND #$1F BNE LF2BB LF27B: LDY #$00 LDX $A2 LDA LFEE6,X AND SWCHB BEQ LF288 INY LF288: STY $94 ; if frameCounter shares bits with $94 LDA frameCounter AND $94 ;Could have used BIT here too. BNE LF297 ; then $AD += $93 LDA $AD CLC ADC $93 STA $AD LF297: LDA $AD CMP #radar1VerPos BCC LF2B5 LDA #$AA STA $AD LDA #$00 STA $B1 STA $E6 LDA $88 BEQ LF2B5 LDA #$3B STA $CB LDA $98 STA $C8 STA $AE LF2B5: LDA $AD BNE LF2BB INC $AD ; if $CD == 3 LF2BB: LDA $CD CMP #$03 BNE LF2E7 ; and $CA == $CE LDA $CA CMP $CE BNE LF2E7 ; then $C7 = $AD - 0x0F ; $AF = $C7 = $AD - 0x0f LDA $AD SEC SBC #$0F STA $C7 STA $AF ;If $8B = 5 then X=1 else X=5 LDX #$05 CPX $8B BEQ LF2D8 LDX #$01 ; $93 = X LF2D8: STX $93 ; $A4 = $A5 + $93 LDA $A5 CLC ADC $93 STA $A4 ; $C6 = $A4 / 2 + 0x58 LSR CLC ADC #$58 STA $C6 LF2E7: RTS LF2E8: LDA $CC STA $94 CMP #$01 BNE LF2F4 LDX #$05 STX $8B LF2F4: CMP #$FF BNE LF2FC LDA #$FB STA $8B LF2FC: LDA $8B LDX #$00 ; If $89 == 5 STX $89 CMP #$05 BNE LF321 ; then go until RTS. STX REFP0 LDA $B4 BNE LRTS3 LDA $A5 CMP #$1F BCC LRTS3 LDA frameCounter AND #$01 BNE LF31A DEC $A5 LF31A: LDA #$01 STA $89 STA $94 RTS ; ; Steer the ship, I think. ; LF321: LDY #$FF STY REFP0 ;Yup, that'll rvs the ship. ; if $B4 == 0 LDA $B4 BNE LRTS3 ; and $A5 < 0x82 LDA $A5 CMP #$82 BCS LRTS3 ; and frameCounter & 1 LDA frameCounter AND #$01 BNE LF337 ; then... INC $A5 LF337: STY $89 STY $94 LRTS3: RTS LF33C: LDA $B4 BNE LRTS3 LDA $8B STA $95 LDA $89 BEQ LF362 LDX #$05 CPX $95 BNE LF350 LDX #$FF LF350: STX $95 LDA #$00 CMP $B6 BEQ LF362 CMP $CC BEQ LF370 CMP $B5 BEQ LF362 STA $94 LF362: LDA $94 BEQ LF370 LDA $B6 CMP #$30 BEQ LF38C INC $B6 BNE LF38C LF370: LDA $B6 BEQ LRTS6 DEC $B6 LDA $B6 BNE LF37C STA $B5 LF37C: LDA $94 BNE LF38C LDX #$01 LDA $95 CMP #$05 BEQ LF38A LDX #$FF LF38A: STX $94 LF38C: LDA $B6 BEQ LRTS6 SED CLC ADC #$0D LSR LSR LSR LSR CLD TAX LDA frameCounter AND LFEB5,X BNE LRTS6 LDA $94 BMI LF3C9 DEC $C9 DEC $C9 DEC $C8 LDA $CD BMI LF3B1 DEC $C6 LF3B1: LDX #$03 LF3B3: LSR CITYGFX+8,X ; 0->[ DC ] -. ROL CITYGFX+4,X ; ,- [ D8 ]<-' ROR CITYGFX,X ; `->[D4]---. LDA CITYGFX,X ; ,---------' AND #$08 ; | BEQ LF3C5 ; | LDA CITYGFX+8,X ; | ORA #$80 ; `->[ DC ] -. STA CITYGFX+8,X LF3C5: DEX BPL LF3B3 LRTS6: RTS LF3C9: INC $C9 INC $C9 INC $C8 LDA $CD BMI LF3D5 INC $C6 LF3D5: LDX #$03 ; This routine performs a 20-bit rotate LF3D7: CLC ROL CITYGFX,X ; ,- [D4] <- 0 ROR CITYGFX+4,X ; `->[D8 ] -. ROL CITYGFX+8,X ; ,- [DC ]<-' BCC LF3E6 ; `-----------. LDA CITYGFX,X ; | ORA #$10 ; Start at bit 4 | STA CITYGFX,X ; [D4] <---' LF3E6: DEX ;Repeat for all four lines of city gfx. BPL LF3D7 RTS LF3EA: LDA $91 BEQ LF3F6 LDA $8D BEQ LF3F6 LDA $3C;INPT4 BPL LF3FC ; if RESET pressed LF3F6: LDA SWCHB ROR BCS LF40C ; then.... LF3FC: LDA bcdGameVariant BPL LF404 INC bcdGameVariant INC bcdGameVariant LF404: JSR LFD3B JSR LFD1C ; $8d = 0x78, $91 = 0x80 BEQ LF444 ; if SELECT not pressed LF40C: ROR BCC LF415 ; then... LDX #$01 STX $E7 BNE LF444 LF415: JSR LFD17 ; $91 = 0xFF JSR LFDE3 DEC $E7 BPL LF444 LDA #$2D STA $E7 LDA bcdGameVariant BPL LF429 INC bcdGameVariant LF429: LDA bcdGameVariant SED ; BCD on CLC ; ADC #$01 ; STA $9B ; Switch to next game variant LDX #$78 ; STX $8D ; LDX #$00 ; STX frameCounter ; Reset frame counter STX $A2 ; CMP #$21 ; Reached variant *21*? BCC StoreNewVariant ; N: Accept new variant LDA #$01 ; Y: Start over with variant *1* STA bcdGameVariant ; Store new variant StoreNewVariant: CLD LF444: LDA #$10 STA NUSIZ0 ; Single-width players, STA NUSIZ1 ; quad-width missiles. LDX gameColors STX COLUBK LDX #$05 ; Ball 1 clock wide LDA frameCounter AND #$0F BNE LF458 LDX #$25 ; Ball 4 clocks wide LF458: STX CTRLPF ; Reflect PLF, over players RTS LF45B: LDA $8D BNE LF463 LDA #$FF STA $91 ;could have done JSR LFD17 ??? LF463: LDA frameCounter BNE LF474 INC $8C LDA $91 BNE LF474 DEC $8D BPL LF474 JSR LFD17 ;$91 = 0xFF LF474: LDA SWCHB LDY #$F7 ; If B&W, X=0x0F. If Color, X=0xFF. LDX #$0F AND #$08 ;COLOR/B&W BEQ LF481 LDX #$FF LF481: LDA $91 BMI LF487 LDY #$FF LF487: AND $8C STA $95 STX $96 STY $97 LDX #$06 LF491: LDA colortable,X EOR $95 AND $96 AND $97 STA gameColors,X DEX BPL LF491 STA CXCLR RTS LF4A2: LDX #$00 LDY #$00 STX AUDV0 LDA $91 BNE LF503 LDA $CB CMP #$97 BEQ LF4F8 BCC LF4C5 ; for Y = 7 to 0 step -1 LDY #$07 ; X = $98 & 7 LF4B6: LDA $98 AND #$07 TAX ; gameColors [Y] = gameColors [X] LDA gameColors,X STA.wy $00E8,Y ; next Y DEY BPL LF4B6 ; goto LF4FA BMI LF4FA LF4C5: LDA $B4 BNE LF4FC LDA $CB CMP #$3C BCS LF508 LDA $CD BPL LF4E6 LDA $AF CMP #$04 BCS LF4E6 LDX #$05 LDA $98 AND #$37 TAY LDA #$0E STA AUDV0 BNE LF503 LF4E6: LDA $8A BEQ LF520 DEC $8A CMP #$20 BCS LF4FA CMP #$1F BNE LF517 STX $8A BEQ LF503 LF4F8: STX $CB ; End skipped code LF4FA: LDA $98 LF4FC: AND #$3F TAY LF4FF: LDX #$08 LF501: STX AUDV0 LF503: STX AUDC0 STY AUDF0 RTS LF508: LDA frameCounter AND #$2F TAY LDX #$01 LDA #$0A STA AUDV0 LDA $D1 BEQ LF503 LF517: LDA frameCounter AND #$22 TAY LDX #$0E BNE LF501 LF520: LDA $AD CMP #$AA BNE LF52A LDA $CB BNE LF4FA LF52A: LDA $E5 BNE LF4FA LDA $CB BNE LF540 LDA JOYSTICK CMP #$F0 BEQ LF540 LDY #$30 LDX #$08 LDA #$03 STA AUDV0 LF540: LDA $E6 BEQ LF549 ROL ROL TAY BNE LF4FF LF549: LDA $B2 CMP #$38 BEQ LF4FA BNE LF503 LF551: LDA $C0 BEQ LF55D LDA $8D BEQ LF55D LDA $91 BNE LF5C8 LF55D: LDY $A2 LDA $9A BEQ LF582 TAX LF564: LDA $9D CLC ADC LFFDB,Y STA $9D DEX BNE LF564 STX $9A AND LFFD9,Y CMP LFFD5,Y BNE LF582 INC $99 LDA $9D AND.wy PLYRJOY,Y STA $9D LF582: LDA $99 BEQ LF5FE ;was LF5FE, assembler hated it. DEC $99 LDX #$02 LF58A: LDA $9C,X CLC ADC LFFDB,Y STA $9C,X AND LFFD9,Y CMP LFFD7,Y BNE LF5A1 LDA $9C,X AND LFFDF,Y STA $9C,X LF5A1: AND LFFD9,Y CMP LFFD5,Y BNE LF5FE LDA $9C,X AND PLYRJOY,Y STA $9C,X INX CPX #$04 BNE LF5B8 JSR LFD25 LF5B8: CPX #$06 BNE LF58A DEX LF5BD: LDA $9C,X AND LFFE1,Y STA $9C,X DEX BPL LF5BD LRTS9: RTS LF5C8: LDX #$0A STX $9D STX $9C LDY #$04 LF5D0: INX STX $9C,Y DEY BPL LF5D0 LDA bcdGameVariant BMI LF5FE LDA $C0 BEQ LF5FE JSR LFE09 STA $9D LDA bcdGameVariant LDX #$01 CMP #$11 BCC LF5EC INX LF5EC: STX $9C AND #$0F STA $A0 ; IF bcdGameVariant & 0xF0 LDA bcdGameVariant AND #$F0 BEQ LF5FE ; then $A1 = bcdGameVariant >> 4 LSR LSR LSR LSR STA $A1 LF5FE: RTS LF5FF: LDA $A5 STA $95 LDA $B1 CMP #$60 BNE LF610 ;$A5 -= $8B LDA $A5 SEC SBC $8B STA $A5 LF610: LDA frameCounter AND #$1F BEQ LRTS7 LDA $E6 BEQ LRTS7 STA $A5 JSR LFD34 LDA #$6B STA $B1 LDA #$1F ;player quad width. missile 8 pixels STA NUSIZ0 LRTS7: RTS LF628: LDA $D1 BEQ LRTS4 LDA $CB CMP #$01 BEQ LRTS4 LDA #$64 STA $B0 LDA #$5D STA $AD LDX #$46 LDA frameCounter AND #$01 BNE LF644 LDX #$4E LF644: STX $A5 STX $A6 LDA $EC STA $8E LDA gameColors STA $8F LDA #$52 STA $B1 LDA enemyWave CPX #$4E BEQ LF665 LSR LSR LSR LSR BNE LF665 LDA #$85 STA $B2 RTS LF665: AND #$0F TAX LDA DIGIND,X STA $B2 LRTS4: RTS ; if $B0 > 128 LF66E: LDA #$80 CMP $B0 BCS LF676 ; then $B0 = 128 STA $B0 LF676: LDX #$04 LDA $A4 BEQ LF68A STA $A7 ; if $CA==$CE then $AF=$AB LDY #$FF LDA $CA CMP $CE BNE LF688 LDY $AF LF688: STY $AB ; ; The divide-by-15 routine uses a simple technique: ; subtract 15 until you run out of 15s. This is ; such a time-consuming task that if the number ; strays from a certain range, the routine could ; take a variable number of scanlines, causing the ; entire picture beneath it to shift as objects ; move. The following lines of code circumvent this ; problem by subtracting the first 75 all at once. ; LF68A: LDY #$00 LDA $A5,X ;$A5 is an array of X positions ; if A > 82 then A-=75 : Y=5 CMP #$52 BCC LF696 SBC #$4B LDY #$05 LF696: CPX #$02 ;a CLC would have sufficed. ADC #$02 ; Do (Y++; A-=15) while A>14 LF69A: INY ; +2 } SBC #$0F ; +2 } * up to 10, -1 BCS LF69A ; +3 } ; A = -A - 8 EOR #$FF ; SBC #$06 ; ; Move low bits to where HMove will see it. ASL ; Get a head-start STA WSYNC ;BEGIN COUNT ASL ; (0) +2 ASL ; (2) +2 ASL ; (4) +2 STA HMP0,X ; (6) +4 Fine-tuning register ; DEY-BPL to get exact distance. LF6AB: DEY ; }(10) BPL LF6AB ; } + Y*5 +4 STA RESP0,X ; *14+5Y* +4 DEX BPL LF68A ;Do players 1 and 0 ; Now to fine-tune the players. STA WSYNC ;COUNT STA HMOVE ; (0) +3 LDY #$05 ; (3) +2 LF6B9: DEY ; }(5) BPL LF6B9 ; } +29 STA HMCLR ; *34* Clear horizontal motion STA WSYNC STA HMOVE ;I don't know why a seocnd hmove? LDA $95 STA $A5 RTS ; Take this time to convert BCD score into ; 0xFF5F+(digit*8) LF6C7: LDY #$00 LDX #$00 LF6CB: LDA $9C,X STX $93 LDX $A2 BEQ LF6D7 LSR LSR LSR LSR LF6D7: AND #$0F LDX $93 STA $94 ASL ASL ASL SEC SBC $94 CLC ADC #$5F STA.wy $00EF,Y LDA #$FF STA.wy $00F0,Y INY INY INX CPX #$06 BNE LF6CB ; Wait for timer to wink out LF6F5: LDA INTIM BNE LF6F5 ; Start main display Screen STA WSYNC ; Finish current line STA VBLANK ; Stop blanking INC frameCounter ; A new frame! LDA radarColor ; A-> P1 objects color in radar STA COLUP1 ; Set color of P1 objects LDA enemyWave ; A-> current enemy wave AND #$03 ; Lowest two bits of wave... TAX ; LDA gameColors+3,X ; ...select radar frame color STA WSYNC ; Finish current line STA COLUPF ; Set radar frame color LDA #$FF ; Draw Top of radar... STA PF2 ; LDA #$01 ; STA PF1 ; ...with the playfield ; Here the actual radar is drawn. Each radarline is two scannlines tall ; The radar shows only two object dots per frame LDY #$0B ; Do 11 radarlines NextRadarLine LDX #$00 ; Assume no radar dot this line STA WSYNC ; Finish current line LDA radarfocus,Y ; A-> C0 v 00 STA PF2 ; Draw focus on top/bottom of radar CPY radar1VerPos ; Show radar dot this line? BNE NoRadarDot ; N: Show nothing DEX ; Y: Show dot NoRadarDot STX ENABL ; En/Disable first dot STA WSYNC ; Finish current line LDX #$00 ; Assume no radar dot this line CPY radar2VerPos ; Show radar dot this line? BNE NoRadarDot2 ; N: Show nothing DEX ; Y: Show dot NoRadarDot2 STX ENAM1 ; En/Disable second dot DEY ; All lines done? BPL NextRadarLine ; N: Do next line STA WSYNC ; Finish current line INY ; Y-> 00 STY ENAM0 ; Prevent bleeding of radar dots... STY ENABL ; ...in case they are still enabled. DEY ; Y-> FF STY PF0 ; STY PF1 ; STY PF2 ; Draw playfield line accross screen LDY #$0F LDX $A2 LDA $CF,X LDX $E9 CMP #$FF BNE LF755 LDY #$00 LDX gameColors LF755: STY $97 STX $96 LDA $8F STA COLUP0 LDA $8E STA COLUP1 LDA #$F0 STA CTRLPF LDY #$84 STA WSYNC ; Clear playfield LDA #$00 STA PF0 STA PF1 STA PF2 ; Beginning of display loop. ; So that you see how tight code has to be, ; I am showing worst possible cycle counts. LF771: LDA #$00 ;(45)+2 (Retroactive branch) CPY $B0 ;(47)+3 BCS LF780 ;(50)+2 LDX $B2 ;(52)+3 LDA GFXDATA,X ;(55)+4 BEQ LF780 ;(59)+2 DEC $B2 ;(61)+5 LF780: CPY $AD ;(66)+3 LDX $B1 ;(70)+3 == *73* CYCLES! STA WSYNC ;BEGIN COUNT (longest-case) STA GRP1 ;*0* +3 BCS LF795 ;(3) +2 If no branches taken LDA SHIPGFX,X ;(5) +4 CMP #$F0 ;(9) +2 BEQ LF795 ;(11)+2 STA GRP0 ;(13)+3 DEC $B1 ;(16)+5 LF795: LDX #$01 ;(21)+2 TYA ;(23)+2 SBC $AB ;(25)+3 AND $92 ;(28)+3 BNE LF79F ;(31)+2 INX ;(33)+2 LF79F: STX ENAM0 ;*35*+3 DEY ;(37)+2 CPY $97 ;(39)+3 BNE LF771 ;(42)+3 (Must take branch to continue) LDA $96 STA COLUPF LDX #$00 STX GRP0 ; Clear ship graphics. ; This display loop does not include the ship, which is ; why the ship is not visible in the cityscape, which we're ; about to draw now. ; X = Y/4 LF7AE: TYA LSR LSR STA WSYNC TAX ; Copy appropriate graphics into playfield. LDA CITYGFX,X STA PF0 LDA CITYGFX+4,X STA PF1 LDA CITYGFX+8,X STA PF2 ; $93 = Y/4 STX $93 LDX #$01 TYA SBC $AB AND $92 BNE LF7CC INX LF7CC: STX ENAM0 LDX $93 DEY BPL LF7AE STA WSYNC LDA #$00 STY PF0 STY PF1 STY PF2 LDX #$01 STX CTRLPF LDY $EE STA WSYNC STY COLUBK STA ENAM0 ;Disable missile 0. STA GRP1 STY COLUP1 STA PF0 STA PF1 STA PF2 STA REFP0 ; Set both players to triple LDA #$03 STA NUSIZ0 STA NUSIZ1 LDY #$06 STX VDELP0 STX VDELP1 STY $93 STY WSYNC LF805: DEY BPL LF805 NOP STA RESP0 STA RESP1 LDA #$F0 STA HMP0 STA WSYNC STA HMOVE LDY #$FE LDA gameColors STA COLUPF STA WSYNC STY PF2 LDX $EC STX COLUP0 STX COLUP1 LF825: LDY $93 ; (61) +3 LDA ($F9),Y ; p0 p1 (64) +5 STA GRP0 ; F9 (69) +3 STA WSYNC ; Cycle count begins LDA ($F7),Y ; (0) +5 STA GRP1 ; F7 (5) +3 LDA ($F5),Y ; (8) +5 STA GRP0 ; F5 (13) +3 LDA ($F3),Y ; (16) +5 STA $94 ; (21) +3 LDA ($F1),Y ; (24) +5 TAX ; (29) +2 LDA ($EF),Y ; (31) +5 TAY ; (36) +2 LDA $94 ; (38) +3 STA GRP1 ; F3 (41) +3 STX GRP0 ; F1 (44) +3 STY GRP1 ; EF (47) +3 STA GRP0 ; F3 (50) +3 DEC $93 ; (53) +5 BPL LF825 ; Branch taken, so (58) +3 ; End six-digit loop LDA #$00 STA VDELP0 ;Clear vertical delays STA VDELP1 STA GRP0 ;Clear players STA GRP1 STA HMP0 ;Clear missiles. STA WSYNC ; Cycle count: STA PF2 ;Clear PF2 [0] LDA $EA ; [3] STA COLUP0 ; [6] STA COLUP1 ; [9] LDY #$08 ; [12] STA RESP0 ; *14* LF867: DEY ;When 8 (17), when 0 (57) BNE LF867 ;At end of loop, (59) STA RESP1 ; (61) ; End result: player 0 is at 0, player 1 is at 120. INY ; Y = 1 STA WSYNC ; The following code amounts to this: ; for Y= 1 to 0 step -1 ; X=$C0 [Y] ; Value for repeat register is indexed from LFEDE ; If number is 0 then do not display that icon. ; next Y LF86F: LDX #$03 LDA.wy $C0,Y CMP #$03 BCS LF879 TAX ;X = $00C0,Y LF879: LDA LFEDE,X STA.wy NUSIZ0,Y ;NUSIZ registar for player Y LDA LFEE2,X STA.wy $96,Y ;AND mask, to be or not to be. DEY BPL LF86F ; Repeat for both players. ; LDX #$0B ;X is separate so that the programmer ;can be a lazy girly-man and index from ;SHIPGFX instead of SHIPGFX+6. LDY #$05 LF88C: STA WSYNC LDA SHIPGFX,X ;Get ship graphics AND $96 ; Only display if $C0 > 0 STA GRP0 LDA BOMBGFX,Y ;Get bomb graphics AND $97 ; Only display if $C1 > 0 STA GRP1 DEX DEY BPL LF88C ; Go until Y runs out. ; Set timer LDA #$26 STA TIM64T ; Reset stack pointer (is it ever used?) LDX #$FF TXS JMP LF04F LF8AB: INC $BB LDA $BB AND #$07 STA $BB TAX JSR LFCA0 ; Y = A = $80 [X] AND 0x0F STA $93 INY LDA $80,X AND #$F0 BEQ LF8C2 LDY #$00 LF8C2: LDA $00E8,Y STA $90 LDY $93 LDA $CD BEQ LF8D6 CPX $B9 BNE LF8D6 LDA $C6 JMP LF8D9 LF8D6: JSR LFCB5 LF8D9: LSR LSR CLC ADC #$2F STA $A8 LDA $CD BEQ LF8ED CPX $B9 BNE LF8ED LDA $C7 JMP LF8F0 LF8ED: JSR LFCCA LF8F0: LSR LSR LSR LSR CLC ADC #$02 STA radar2VerPos LDY $A2 LDA #$FF STA radar1VerPos CMP.wy $00CF,Y BEQ LF949 INC $CE LDA $CE CMP #$05 BCC LF910 LDA #$00 STA $CE LF910: TAX LDA.wy $00CF,Y AND LFF12,X BNE LF949 LDA $C9 CLC ADC TIMES40,X LSR LSR CLC ADC #$30 STA $A9 LDA #$01 STA radar1VerPos LDA $CD BEQ LF949 LDA $CA CMP $CE BNE LF949 LDA $CD BMI LF949 LDA $C7 LSR LSR LSR LSR STA radar1VerPos LDA $C6 LSR LSR CLC ADC #$30 STA $A9 LF949: LDA frameCounter AND #$0F BNE LF968 LDA #$FF STA $CE LDA $AD LSR LSR LSR LSR STA radar1VerPos LDA $A5 LSR CLC ADC #$58 LSR LSR CLC ADC #$2F STA $A9 LF968: RTS LF969: LDA #$00 STA $A4 LDY $A2 LDA $00CF,Y CMP #$FF BEQ LF9A1 AND LFF12,X BNE LF9A1 LDA $C9 CLC ADC TIMES40,X CPX $CA BNE LF98D LDY $CD BPL LF98B STA $C6 LF98B: LDA $C6 LF98D: CMP #$59 BCC LF9A1 CMP #$A8 BCS LF9A1 SEC SBC #$58 STA $94 CLC ADC $94 ADC #$02 STA $A4 LF9A1: RTS LF9A2: LDY #$07 STY $94 LDA $A6 STA $95 LDA $B7 STA $96 LDA $B0 STA $97 LF9B2: INC $B7 LDA $B7 AND #$07 STA $B7 TAX LDA $80,X BMI LF9D3 AND #$0F TAY JSR LFCB5 CPX $B9 BNE LF9CB LDA $C6 LF9CB: CMP #$59 BCC LF9D3 CMP #$A5 BCC LF9E0 LF9D3: DEC $94 BPL LF9B2 LDA #$FF STA $B7 LDA #$00 STA $A6 RTS LF9E0: JSR LFCCA CPX $B9 BNE LF9E9 LDA $C7 LF9E9: STA $B0 JSR LFCB5 CPX $B9 BNE LF9F4 LDA $C6 LF9F4: SEC SBC #$58 ASL STA $A6 RTS LF9FB: JSR LFDEE LDX $B7 BMI LFA4E STY $B8 INY LDA $00E8,Y STA $8E DEY LDA TIMES8,Y STA $B2 LDA $CD CMP #$03 BNE LFA24 LDA #$25 CMP enemyWave BNE LFA24 CMP $AD BCC LFA24 LDA #$AE STA $B2 LFA24: LDA $80,X AND #$10 BEQ LFA4E LDA #$38 STA $B2 CPX $B9 BNE LFA34 STA $B9 LFA34: JSR LFCA0 LDA #$80 STA $80,X CPY #$02 BNE LFA4E LDA $E5 BNE LFA4E INY STY $80,X STA $B2 LDA $80 BPL LFA4E STY $80 LFA4E: RTS LFA4F: LDA $91 BNE LFABF LDA $B4 BNE LFA90 STA $93 LDA $E6 BNE LFA4E LDA $30 AND #$40 ; M0 - P0 BEQ LFA7E LDX $92 CPX #$FC BNE LFA7C STA $B9 LDX $CD CPX #$02 BNE LFA7C INC $CD LDX #$05 STX $99 JSR LFD2F LDA #$00 ;Clear collision LFA7C: STA $93 LFA7E: LDA $37 BPL LFA84 ;Branch if players don't collide STA $93 ;Mark collision LFA84: LDA $93 BEQ LFA90 LDA #$00 STA $B6 LDA #$1E STA $B4 LFA90: LDY $B4 BEQ LRTS5 LDA frameCounter AND #$03 BNE LFA9C DEC $B4 LFA9C: JSR LFD34 CPY #$05 BCS LRTS5 LDA LFE89,Y STA $B1 LDA $B4 BNE LRTS5 JSR LF1C9 LDA #$32 STA $CB JSR LFCAC LDX $A2 DEC $C2,X BNE LFABF JSR LFCEB LFABF: LDA $C2 ;Any lives left, player 1? BNE LRTS5 LDA bcdGameVariant CMP #$11 BCC LFAD9 LDA $C3 ;Any lives left, player 2? BNE LRTS5 LDA frameCounter AND #$1F BNE LFAD9 LDA $A2 EOR #$01 STA $A2 LFAD9: JSR LFD17 LRTS5: RTS ; ; Notice that LDA is used here in order to test bit 7. ; Combat, which predates Defender by four years, uses ; BIT. ; ; This routine is only executed when $91 equals zero. ; LFADD: LDX $96 LDA $B2 CMP #$38 BEQ LFB36 LDA $80,X BMI LFAED LDA $37 ;Collision between players & missiles BMI LFB02 LFAED: LDA $E5 BEQ LFB36 LDA $99 BNE LFB36 LDX $B7 BPL LFB02 LDX $A2 DEC $C4,X LDA #$00 STA $E5 RTS LFB02: JSR LFCA0 LDA #$00 STA $E6 LDA LFEFA,Y STA $9A LDA LFF00,Y STA $99 ; Set bit 4 across $80 field. LDA $80,X ORA #$10 STA $80,X CPX $B9 BNE LFB36 LDA $CD BPL LFB28 LDA $AF BPL LFB28 INC $CD RTS LFB28: LDA #$02 STA $CD STA $BA LDA #$32 CMP $C7 BCS LFB36 STA $BA LFB36: RTS ; ; This routine is called only when $91 equals zero. ; LFB37: LDA $B4 BNE LFB8F LDX $A2 LDA $3C,X BPL LFB4A LDA #$00 STA $88 LFB45: LDA $E6 BNE LFB69 RTS LFB4A: LDA $88 BNE LFB45 JSR LFD1C DEC $88 LDA #$14 CMP $AD BCS LFB83 LDA $A5 SEC SBC #$02 STA $E6 LDX $8B BPL LFB69 SEC SBC #$17 STA $E6 LFB69: LDX #$07 LDA $8B BPL LFB71 LDX #$F9 LFB71: TXA CLC ADC $E6 TAX CMP #$82 BCS LFB7E CMP #$00 BCS LFB80 LFB7E: LDX #$00 LFB80: STX $E6 RTS ; if ($C1 != 0 && $B7 != 0xFF) ; $E5 = 0xFF ; LFB83: LDA $C1 BEQ LFB8F LDA #$FF CMP $B7 BEQ LFB8F STA $E5 LFB8F: RTS LFB90: LDX #$A0 LDY #$00 LDA #$FC STA $92 LDA $A4 BNE LFC07 LDA $BF BNE LFBD2 LDA $B7 BMI LFC07 LDY $B8 CPY #$02 BEQ LFC07 LDX #$01 LDA $B0 STA $BC CMP $AD BCC LFBB6 LDX #$FF LFBB6: STX $BE LDA $8A BNE LFBBE INC $8A ;$8A = 1 LFBBE: LDA $A6 STA $BD CMP $A5 BCC LFBC8 LDX #$FE LFBC8: STX $BF CPY #$00 BNE LFBD2 LDA #$F0 STA $BF ; Branched here if $BF is zero. LFBD2: LDX $BC LDY $BD CMP #$F0 BNE LFBE2 LDA frameCounter AND #$5A BEQ LFBFD BNE LFC03 LFBE2: TXA CLC ADC $BE STA $BC CMP #$0F BCC LFBFD TAX LDA $BD CLC ADC $BF STA $BD TAY LDA $B4 BNE LFBFD CPY #$A0 BCC LFC03 LFBFD: LDY #$00 STY $BF LDX #$A0 LFC03: LDA #$FE STA $92 ;Branched here if $A4 or $B7 is zero. LFC07: STX $AB STY $A7 RTS ; for X=7 to 0 step -1 LFC0C: LDX #$07 LFC0E: LDA $80,X BPL LFC42 DEX BPL LFC0E LDA #$00 TAY CLC ADC $9A ADC $99 ADC $B4 BNE LFC42 LDX $A2 LDA $CF,X LDX #$07 LFC27: ROR BCS LFC2B INY LFC2B: DEX BPL LFC27 STY $99 LDA #$96 STA $CB STA $D1 STA $B9 LDA $E5 BEQ LFC42 LDX $A2 DEC $C4,X INC $E5 LFC42: RTS LFC43: LDA $D3 BEQ LFC7A LDA $98 AND #$07 TAX CPX $B9 BEQ LFC7A LDA $80,X BPL LFC7A LDY $A2 LDA $00CF,Y CMP #$FF BNE LFC61 LDY #$05 BNE LFC6B LFC61: LDY #$04 LDA frameCounter AND #$1F BNE LFC6B LDY #$01 LFC6B: JSR LFCB5 CMP #$59 BCC LFC76 CMP #$A8 BCC LFC7A LFC76: STY $80,X DEC $D3 LFC7A: RTS LFC7B: JSR LFCA6 LDA LFEC4,X STA $93 CPX #$00 BEQ LFC9F LDX enemyWave STY $97 LDY #$01 CPX #$07 BCC LFC92 DEY LFC92: DEX BEQ LFC9D CPY $93 BEQ LFC9D LSR $93 BNE LFC92 LFC9D: LDY $97 LFC9F: RTS LFCA0: LDA $80,X AND #$0F TAY RTS LFCA6: LDA bcdGameVariant AND #$0F TAX RTS ; ; Clear radar1VerPos, $AB, and radar2VerPos with #$A0. ; LFCAC: LDA #$A0 STA $AB STA radar2VerPos STA radar1VerPos RTS ; ; IF LFF06[Y] = 3 ; LFCB5: STX $93 ; X= LFF06 [Y] LDX LFF06,Y LDA #$00 ;if X <> 3 CPX #$03 BEQ LFCC2 ; then A=$E0 [X] LDA $E0,X ; A += $C8 + $93 * 40 LFCC2: LDX $93 ADC $C8 ADC TIMES40,X RTS ; ;If LFF0C[Y] = 3 ; A = ( $AE + $93 *40 ) / 2 + 24 ;Else ; A = ( $E3[X] + $AE + $93 *40 ) / 2 + 24 ; LFCCA: STX $93 LDX LFF0C,Y LDA #$00 CPX #$03 BEQ LFCD7 LDA $E3,X LFCD7: LDX $93 ADC $AE ADC TIMES40,X LSR CLC ADC #$18 LFCE2: RTS LFCE3: LDA $D1 BEQ LFCE2 LDA #$00 STA $D1 LFCEB: LDA bcdGameVariant CMP #$11 BCC LFD09 LDA $A2 EOR #$01 TAX LDA $C2,X BEQ LFD09 STX $A2 CPX #$01 BNE LFD09 ; Decrease enemyWave by one, in decimal. SED LDA enemyWave SEC SBC #$01 STA enemyWave CLD LFD09: JMP LFD73 ; Executed when enemyWave is a multiple of 5 ; (in decimal mode). bcdGameVariant is initialized ; to $FF on power-up. LFD0C: JSR LFCA6 ; X = bcdGameVariant AND 0x0F LDA LFECD,X STA $CF STA $D0 RTS LFD17: LDA #$FF STA $91 RTS ; Result of this is stored in $A2. LFD1C: LDA #$78 STA $8D LDA #$00 STA $91 RTS ; I have a hunch that this is the "extra man" ; routine. If so, $C4 and $C2 represent a ; player's extra lives and smart bomb supply. LFD25: STX $93 LDX $A2 INC $C4,X INC $C2,X LDX $93 LFD2F: LDA #$1E ;Called when $BA != 0x32 STA $8A RTS ; $8F = gameColors [$BB] LFD34: LDX $BB LDA gameColors,X STA $8F RTS ; This is the first subroutine ever called in this ; program. ; ; The fact that certain locations are cleared ; here implies that this is called more than once. LFD3B: LDA #$00 STA $A2 STA $D1 STA $CD STA $A4 STA $9A STA $99 STA $B4 STA REFP0 ;Aim ship to the right. LDA #$96 STA $CB JSR LFDE3 JSR LFE09 JSR LFD0C LDA LFEE8,X STA enemyWave ; Copy in city graphics. ; I don't know why it uses four-byte chunks. ; It could just copy all twelve bytes in a row. LDX #$03 LFD61: LDA ROMCITY,X STA CITYGFX,X LDA ROMCITY+4,X STA CITYGFX+4,X LDA ROMCITY+8,X STA CITYGFX+8,X DEX BPL LFD61 LFD73: LDA $98 ;This byte is set to $FF on powerup. STA $C9 STA $E3 STA $E4 STA $AE ; This seems to set up indexes. LDA #$00 STA $B6 STA $BD STA $BF STA $CD LDA #$FE STA $92 STA $B9 STA $CA LDA enemyWave AND #$0F BEQ LFD99 CMP #$05 BNE LFD9C LFD99: JSR LFD0C ;Executed if low nybble ;is 0 or 5. ; Add 1 in decimal. LFD9C: SED LDA enemyWave CLC ADC #$01 STA enemyWave CLD LDA #$0F STA $D3 LDX #$07 LFDAB: LDA LFF18,X STA $80,X LDY $A2 ;Y is initialized during ;each iteration, needlessly. ;I expected better. LDA $00CF,Y CMP #$FF BNE LFDBD LDA #$05 STA $80,X LFDBD: DEX BPL LFDAB JSR LFDEE LFDC3: LDA #$32 STA $AD LDA #$1E STA $A5 JSR LFCAC ;Load radar1VerPos, $AB, and radar2VerPos with 0xA0 STA $C8 STA $AB LDA #$05 STA $8B LDA #$00 ;Again with LDA #$00.... ;I'm sure they could have ;consolidated this into an earlier ;section of code. STA $E0 STA $E1 STA $E2 STA $CC STA $E6 RTS ;Clear $C2 through $C5 with $03 LFDE3: LDA #$03 STA $C2 STA $C3 STA $C4 STA $C5 RTS ; Some relatively simple function whose purpose ; I shall discover shortly. ;if $B4 == 0 ;and ( frameCounter & 7 ) == 0 ;then $B1 = 0x60; $8F = $EE ;else $B1 = 0x10; $8F = $EA LFDEE: LDA #$10 STA $B1 LDA $EA STA $8F LDA $B4 BNE LFE08 LDA frameCounter AND #$07 BNE LFE08 LDA #$60 STA $B1 LDA $EE STA $8F LFE08: RTS ; I presume this routine hides the score ; display in order to select a level. ; ; $9C = $9D = 0 ; $9E = $9F = $A0 = $A1 = #$AA LFE09: LDA #$00 STA $9C STA $9D LDA #$AA STA $9E STA $9F STA $A0 STA $A1 RTS SHIPGFX: .byte $F0 ; |XXXX | $FE1A .byte $00 ; | | $FE1B .byte $00 ; | | $FE1C .byte $00 ; | | $FE1D .byte $00 ; | | $FE1E .byte $00 ; | | $FE1F .byte $00 ; | | $FE20 .byte $38 ; | XXX | $FE21 .byte $7F ; | XXXXXXX| $FE22 Exhaust .byte $7C ; | XXXXX | $FE23 .byte $70 ; | XXX | $FE24 .byte $20 ; | X | $FE25 .byte $00 ; | | $FE26 .byte $00 ; | | $FE27 .byte $00 ; | | $FE28 .byte $00 ; | | $FE29 .byte $00 ; | | $FE2A .byte $F0 ; |XXXX | $FE2B .byte $00 ; | | $FE2C .byte $00 ; | | $FE2D .byte $00 ; | | $FE2E .byte $04 ; | X | $FE2F .byte $08 ; | X | $FE30 .byte $44 ; | X X | $FE31 .byte $28 ; | X X | $FE32 Exploding ship .byte $26 ; | X XX | $FE33 .byte $1C ; | XXX | $FE34 .byte $28 ; | X X | $FE35 .byte $04 ; | X | $FE36 .byte $20 ; | X | $FE37 .byte $00 ; | | $FE38 .byte $00 ; | | $FE39 .byte $00 ; | | $FE3A .byte $F0 ; |XXXX | $FE3B .byte $00 ; | | $FE3C .byte $00 ; | | $FE3D .byte $08 ; | X | $FE3E .byte $00 ; | | $FE3F .byte $42 ; | X X | $FE40 .byte $20 ; | X | $FE41 .byte $04 ; | X | $FE42 .byte $41 ; | X X| $FE43 .byte $10 ; | X | $FE44 .byte $42 ; | X X | $FE45 .byte $08 ; | X | $FE46 .byte $40 ; | X | $FE47 .byte $02 ; | X | $FE48 .byte $20 ; | X | $FE49 .byte $00 ; | | $FE4A .byte $F0 ; |XXXX | $FE4B .byte $00 ; | | $FE4C .byte $10 ; | X | $FE4D .byte $02 ; | X | $FE4E .byte $40 ; | X | $FE4F .byte $00 ; | | $FE50 .byte $41 ; | X X| $FE51 .byte $00 ; | | $FE52 .byte $20 ; | X | $FE53 .byte $02 ; | X | $FE54 .byte $00 ; | | $FE55 .byte $40 ; | X | $FE56 .byte $04 ; | X | $FE57 .byte $00 ; | | $FE58 .byte $40 ; | X | $FE59 .byte $12 ; | X X | $FE5A .byte $F0 ; |XXXX | $FE5B .byte $00 ; | | $FE5C .byte $01 ; | X| $FE5D .byte $40 ; | X | $FE5E .byte $00 ; | | $FE5F .byte $00 ; | | $FE60 .byte $00 ; | | $FE61 .byte $00 ; | | $FE62 .byte $00 ; | | $FE63 .byte $01 ; | X| $FE64 .byte $00 ; | | $FE65 .byte $00 ; | | $FE66 .byte $00 ; | | $FE67 .byte $40 ; | X | $FE68 .byte $00 ; | | $FE69 .byte $21 ; | X X| $FE6A .byte $F0 ; |XXXX | $FE6B .byte $FF ; |XXXXXXXX| $FE6C .byte $00 ; | | $FE6D .byte $00 ; | | $FE6E .byte $F0 ; |XXXX | $FE6F .byte $00 ; | | $FE70 .byte $7C ; | XXXXX | $FE71 Exhaust .byte $FE ; |XXXXXXX | $FE72 .byte $3C ; | XXXX | $FE73 .byte $3C ; | XXXX | $FE74 .byte $FE ; |XXXXXXX | $FE75 .byte $7C ; | XXXXX | $FE76 .byte $00 ; | | $FE77 .byte $00 ; | | $FE78 .byte $00 ; | | $FE79 .byte $00 ; | | $FE7A .byte $F0 ; |XXXX | $FE7B .byte $00 ; | | $FE7C .byte $FE ; |XXXXXXX | $FE7D .byte $7F ; | XXXXXXX| $FE7E .byte $00 ; | | $FE7F .byte $00 ; | | $FE80 .byte $00 ; | | $FE81 .byte $00 ; | | $FE82 ; Bomb graphics BOMBGFX: .byte $00 ; | | $FE83 .byte $00 ; | | $FE84 .byte $00 ; | | $FE85 .byte $5C ; | X XXX | $FE86 .byte $3E ; | XXXXX | $FE87 .byte $5C ; | X XXX | $FE88 LFE89: .byte $00,$50,$40,$30,$20 LFE8E: .byte $F0,$E0,$D0,$70,$B0,$60,$50,$90,$A0 LFE97: .byte $00,$01,$FF,$00,$00,$01,$FF,$FF,$01 LFEA0: .byte $00,$00,$00,$01,$FF,$01,$01,$FF,$FF ; PF2 values that create the radar body with focus in the middle radarfocus: .byte $C0,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$C0 LFEB5: .byte $FF,$07,$03,$01,$01 ; Index values for digits 0 through 9 DIGIND: .byte $3F,$46,$4D,$54,$5B,$62,$69,$70,$77,$7E LFEC4: .byte $0F,$07,$03,$07,$07,$03,$07,$07,$03 ;Indexed by (bcdGameVariant AND 0x0F) LFECD: .byte $07,$07,$07,$FF,$07,$07,$FF,$07 .byte $07,$FF,$07,$07,$07,$07,$07,$07 .byte $07 ;Extra byte. Will investigate. ; Copied to NUSIZ registers LFEDE: .byte $F0,$F0,$F1,$F3 ; Copied to $96 and $97. LFEE2: .byte $00,$FF,$FF,$FF ; 0x40 << X LFEE6: .byte $40,$80 LFEE8: .byte $00,$00,$00,$00,$02,$02,$02,$04,$04,$04 ; 0x28 * X or 40 * x TIMES40: .byte $00,$28,$50,$78,$9B,$AF,$64,$5A ; Some wacky indexing happens here. LFEFA: .byte $05,$00,$00,$00,$05,$05 LFF00: .byte $02,$02,$0A,$05,$01,$01 LFF06: .byte $03,$00,$02,$00,$02,$01 LFF0C: .byte $01,$00,$03,$00,$03,$00 ; 0x80 >> X LFF12: .byte $80,$40,$20,$10,$08,$04 ;These eight bytes are copied into $80, ;with some exceptions. LFF18: .byte $00,$02,$02,$04,$04,$04,$04,$80 ; (X+1) * 8 table TIMES8: .byte $08,$10,$18,$20,$28,$30 ; Graphics are stored here. GFXDATA: .byte $00 ; | | $FF26 ; Minelayer .byte $00 ; | | $FF27 .byte $00 ; | | $FF28 .byte $00 ; | | $FF29 .byte $00 ; | | $FF2A .byte $F8 ; |XXXXX | $FF2B .byte $D8 ; |XX XX | $FF2C .byte $D8 ; |XX XX | $FF2D .byte $F8 ; |XXXXX | $FF2E .byte $00 ; | | $FF2F ; Baiter .byte $00 ; | | $FF30 .byte $00 ; | | $FF31 .byte $00 ; | | $FF32 .byte $00 ; | | $FF33 .byte $7E ; | XXXXXX | $FF34 .byte $E7 ; |XXX XXX| $FF35 .byte $7E ; | XXXXXX | $FF36 .byte $00 ; | | $FF37 ; Thing that splits into swarmers .byte $10 ; | X | $FF38 .byte $54 ; | X X X | $FF39 .byte $38 ; | XXX | $FF3A .byte $FE ; |XXXXXXX | $FF3B .byte $38 ; | XXX | $FF3C .byte $54 ; | X X X | $FF3D .byte $10 ; | X | $FF3E .byte $00 ; | | $FF3F ; Swarmer .byte $42 ; | X X | $FF40 .byte $E7 ; |XXX XXX| $FF41 .byte $42 ; | X X | $FF42 .byte $04 ; | X | $FF43 .byte $4E ; | X XXX | $FF44 .byte $E4 ; |XXX X | $FF45 .byte $40 ; | X | $FF46 .byte $00 ; | | $FF47 ; Lander .byte $FF ; |XXXXXXXX| $FF48 .byte $7E ; | XXXXXX | $FF49 .byte $24 ; | X X | $FF4A .byte $18 ; | XX | $FF4B .byte $3C ; | XXXX | $FF4C .byte $3C ; | XXXX | $FF4D .byte $18 ; | XX | $FF4E .byte $00 ; | | $FF4F ; Mutant .byte $C3 ; |XX XX| $FF50 .byte $3C ; | XXXX | $FF51 .byte $24 ; | X X | $FF52 .byte $18 ; | XX | $FF53 .byte $3C ; | XXXX | $FF54 .byte $3C ; | XXXX | $FF55 .byte $44 ; | X X | $FF56 .byte $00 ; | | $FF57 .byte $10 ; | X | $FF58 .byte $20 ; | X | $FF59 .byte $40 ; | X | $FF5A .byte $14 ; | X X | $FF5B .byte $28 ; | X X | $FF5C .byte $54 ; | X X X | $FF5D .byte $20 ; | X | $FF5E ; 0 .byte $7E ; | XXXXXX | $FF5F .byte $72 ; | XXX X | $FF60 .byte $72 ; | XXX X | $FF61 .byte $72 ; | XXX X | $FF62 .byte $72 ; | XXX X | $FF63 .byte $72 ; | XXX X | $FF64 .byte $7E ; | XXXXXX | $FF65 ; 1 .byte $1C ; | XXX | $FF66 .byte $1C ; | XXX | $FF67 .byte $1C ; | XXX | $FF68 .byte $1C ; | XXX | $FF69 .byte $1C ; | XXX | $FF6A .byte $1C ; | XXX | $FF6B .byte $3C ; | XXXX | $FF6C ; 2 .byte $7E ; | XXXXXX | $FF6D .byte $40 ; | X | $FF6E .byte $7E ; | XXXXXX | $FF6F .byte $0E ; | XXX | $FF70 .byte $0E ; | XXX | $FF71 .byte $4E ; | X XXX | $FF72 .byte $7E ; | XXXXXX | $FF73 ; 3 .byte $7E ; | XXXXXX | $FF74 .byte $4E ; | X XXX | $FF75 .byte $0E ; | XXX | $FF76 .byte $1C ; | XXX | $FF77 .byte $0E ; | XXX | $FF78 .byte $4E ; | X XXX | $FF79 .byte $7E ; | XXXXXX | $FF7A ; 4 .byte $1C ; | XXX | $FF7B .byte $1C ; | XXX | $FF7C .byte $7E ; | XXXXXX | $FF7D .byte $5C ; | X XXX | $FF7E .byte $5C ; | X XXX | $FF7F .byte $5C ; | X XXX | $FF80 .byte $7C ; | XXXXX | $FF81 ; 5 .byte $7E ; | XXXXXX | $FF82 .byte $4E ; | X XXX | $FF83 .byte $0E ; | XXX | $FF84 .byte $7E ; | XXXXXX | $FF85 .byte $40 ; | X | $FF86 .byte $4E ; | X XXX | $FF87 .byte $7E ; | XXXXXX | $FF88 ; 6 .byte $7E ; | XXXXXX | $FF89 .byte $4E ; | X XXX | $FF8A .byte $4E ; | X XXX | $FF8B .byte $7E ; | XXXXXX | $FF8C .byte $40 ; | X | $FF8D .byte $4E ; | X XXX | $FF8E .byte $7E ; | XXXXXX | $FF8F ; 7 .byte $0E ; | XXX | $FF90 .byte $0E ; | XXX | $FF91 .byte $0E ; | XXX | $FF92 .byte $0E ; | XXX | $FF93 .byte $0E ; | XXX | $FF94 .byte $4E ; | X XXX | $FF95 .byte $7E ; | XXXXXX | $FF96 ; 8 .byte $7E ; | XXXXXX | $FF97 .byte $4E ; | X XXX | $FF98 .byte $4E ; | X XXX | $FF99 .byte $7E ; | XXXXXX | $FF9A .byte $72 ; | XXX X | $FF9B .byte $72 ; | XXX X | $FF9C .byte $7E ; | XXXXXX | $FF9D ; 9 .byte $7E ; | XXXXXX | $FF9E .byte $72 ; | XXX X | $FF9F .byte $02 ; | X | $FFA0 .byte $7E ; | XXXXXX | $FFA1 .byte $72 ; | XXX X | $FFA2 .byte $72 ; | XXX X | $FFA3 .byte $7E ; | XXXXXX | $FFA4 ; Space .byte $00 ; | | $FFA5 .byte $00 ; | | $FFA6 .byte $00 ; | | $FFA7 .byte $00 ; | | $FFA8 .byte $00 ; | | $FFA9 .byte $00 ; | | $FFAA .byte $00 ; | | $FFAB ; (C) 1981 Atari .byte $79 ; | XXXX X| $FFAC .byte $85 ; |X X X| $FFAD .byte $B5 ; |X XX X X| $FFAE .byte $A5 ; |X X X X| $FFAF .byte $B5 ; |X XX X X| $FFB0 .byte $85 ; |X X X| $FFB1 .byte $79 ; | XXXX X| $FFB2 .byte $17 ; | X XXX| $FFB3 .byte $15 ; | X X X| $FFB4 .byte $15 ; | X X X| $FFB5 .byte $77 ; | XXX XXX| $FFB6 .byte $55 ; | X X X X| $FFB7 .byte $55 ; | X X X X| $FFB8 .byte $77 ; | XXX XXX| $FFB9 .byte $41 ; | X X| $FFBA .byte $41 ; | X X| $FFBB .byte $41 ; | X X| $FFBC .byte $41 ; | X X| $FFBD .byte $41 ; | X X| $FFBE .byte $41 ; | X X| $FFBF .byte $40 ; | X | $FFC0 .byte $49 ; | X X X| $FFC1 .byte $49 ; | X X X| $FFC2 .byte $49 ; | X X X| $FFC3 .byte $C9 ; |XX X X| $FFC4 .byte $49 ; | X X X| $FFC5 .byte $49 ; | X X X| $FFC6 .byte $BE ; |X XXXXX | $FFC7 .byte $55 ; | X X X X| $FFC8 .byte $55 ; | X X X X| $FFC9 .byte $55 ; | X X X X| $FFCA .byte $D9 ; |XX XX X| $FFCB .byte $55 ; | X X X X| $FFCC .byte $55 ; | X X X X| $FFCD .byte $99 ; |X XX X| $FFCE ; Author's initials .byte $00 ; | | $FFCF .byte $C4 ; |XX X | $FFD0 .byte $A4 ; |X X X | $FFD1 .byte $C6 ; |XX XX | $FFD2 .byte $A5 ; |X X X X| $FFD3 .byte $C6 ; |XX XX | $FFD4 LFFD5: .byte $0A,$A0 LFFD7: .byte $0B,$B0 LFFD9: .byte $0F,$F0 LFFDB: .byte $01,$10 PLYRJOY: .byte $F0,$0F LFFDF: .byte $F1,$1F LFFE1: .byte $FA,$AF ; City graphics in ROM. ; Arrangement is a bit tricky to explain. ROMCITY: .byte $E0,$60,$40,$40 ;...1 .... .11. .... ..1. .byte $7B,$79,$59,$10 ;.1.1 1..1 .11. .11. ..1. .byte $CE,$C6,$C6,$C0 ;.111 1..1 .11. .11. .11. ;.111 1.11 .11. .111 .111 ; Remember that PF1 is reversed. colortable: .byte $00,$88,$8F,$FF,$1D,$1A,$37,$00 .byte $00,$00,$00,$00,$00 .word START .word START