›;SET VERTICAL BLANK VECTOR›SETVBV  EQU    $E45C›;VERTICAL BLANK TEXT VECTOR›XITVBV  EQU    $E462›;›;  --------------------------------›;   ZERO PAGE REGISTERS VARIABLES›;  --------------------------------›;›     ORG   $CB›VAR1  DB    0›VAR2  DB    0›VAR3  DB    0›ADD1  DS    2›ADD2  DS    2›;›;›;›;  --------------------------------›;   PROGRAM STORAGE LOCATIONS›;  --------------------------------›;›     ORG   $600›PVERT    DB   0,0,0,0›MVERT    DB   0,0,0,0›POLDVERT DB   0,0,0,0›MOLDVERT DB   0,0,0,0›;›;›;PLAYER TABLE ADDRESS TABLE›PLAYER›         DB   0,0›         DB   0,0›         DB   0,0›         DB   0,0›;›;MISSILE TABLE ADDRESS TABLE›MISSILE›         DB   0,0›;›;ON/OFF SWITCH›SWITCH   DB   0›;›;PLAYER IMAGE ADDRESS TABLE›IMAGE›         DW   IMAGES0›         DW   IMAGE1›         DW   IMAGE2›         DW   IMAGE3›;›;IMAGE DEFINITION TABLE›;›; IMAGES›IMAGE0   DB   0,0,0,0,0›         DB   0,0,0,0,0›IMAGE1   DB   0,0,0,0,0›         DB   0,0,0,0,0›IMAGE2   DB   0,0,0,0,0›         DB   0,0,0,0,0›IMAGE3   DB   0,0,0,0,0›         DB   0,0,0,0,0›;›;PLAYER SIZE TABLE›PSIZE    DB   0,0,0,0›;  -------------------------------›;   INITIALIZE THE PM ROUTINE›;  -------------------------------›;›; THIS IS THE BASIC ENTRY POINT›         PLA›;›; SETUP THE VERTICAL BLANK INTERUPT›; JUMP VECTOR›         LDX  #HIGH VB›         LDY  #LOW VB›         LDA  #7›         JSR  SETVBV›         RTS›;›;  -------------------------------›;   VERTICAL BLANK ROUTINE  (PM)›;  -------------------------------›;›VB›      LDA  SWITCH ;CHECK IF THE SWITCH IS ON›      BNE  VB1    ;IF NOT THEN JUST RETURN›      JSR  MPLOT  ;CALL THE MISSILE PLOT ROUTINE›      JSR  PPLOT  ;CALL THE PLAYER PLOT ROUTINE›VB1   JMP  XITVBV›;›;›; THIS IS THE ROUTINE TO PLOT THE›; PLAYERS›PPLOT:›      LDA  #3  ;SET THE PLAYER COUNT›      STA  VAR1 ; AND SAVE IT IN VAR1›PPLOT0:›      LDX  VAR1 ;GET THE CURRENT PLAYER NUMBER›      LDA PVERT,X ;GET THE NEW Y›      COOR›      STA  VAR3 ; AND SAVE IT IN VAR3›      LDY  POLDVERT,X ;GET THE OLD Y COOR›      STA  POLDVERT,X ;STORE THE NEW Y COOR AS THE OLD›      LDA  PSIZE,X ;GET THE SIZE OF THE CURRENT PLAYER›      STA  VAR2   ; AND STORE IT IN VAR2›      TXA       ;MULTIPLY THE PLAYER NUMBER›      ASL  A    ; BY 2›      TAX›      LDA  PLAYER,X  ;MOVE THE ADDRESS OF THE PLAYER›      STA  ADD1  ; TO THE TEMPORARY REGISTER (ADD1)›      LDA  PLAYER+1,X›      STA  ADD1+1›      LDA  IMAGE,X  ;MOVE THE ADDRESS OF THE IMAGE›      STA  ADD2  ; TO THE TEMPORARY REGISTER (ADD2)›      LDA  IMAGE+1,X›      STA  ADD2+1›; THIS SECTION OF CODE IS USED›;TO ERASE THE PLAYER FROM HIS›;OLD POSITION›      LDX  VAR2   ;LOAD X WITH THE SIZE OF THE PLAYER›      LDA  #0›PPLOT1›      STA  (ADD1),Y ;STORE ZERO›      DEY          ;DECREMENT THE BYTE POSITION COUNTER›      CPY  #$FF›      BEQ  PPLOT2  ;IF EQUAL WE'VE HIT THE TOP OF THE PLAYER›      DEX          ;DECREMENT THE SIZE COUNTER›      BPL  PPLOT1  ;IF STILL POSITIVE ZERO THE NEXT BYTE›;›;THIS PART OF THE CODE IS USED TO›;PLOT THE PLAYER 'N HIS NEW LOCATION›PPLOT2›      LDY  VAR2  ;GET THE IMAGE OFF›      SET›      LDA  (ADD2),Y  ;GET THE NEXT IMAGE BYTE›      LDY  VAR3   ;GET THE PLAYER TABLE OFFSET›      STA  (ADD1),Y  ;PUT THE IMAGE BYTE IN THE PLAYER TABLE›      DEY      ;DECREMENT THE PLAYER TABLE OFFSET›      STY  VAR3   ;STORE THE NEW PLAYER TABLE OFFSET›      CPY  #$FF   ;IF THE NEXT BYTE WOULD BE OFF THE END›               ;OF THE PLAYER THEN EXIT THE PLOT LOOP›      BEQ  PPLOT3›      DEC  VAR2   ;DECREMENT THE IMAGE OFFSET›      BPL  PPLOT2  ;IF WE HAVE NOT REACHED THE END THEN›                  ;LOOP AGAIN TO PLOT ANOTHER IMAGE BYTE›PPLOT3›      DEC  VAR1   ;DECREMENT THE PLAYER COUNT›      BPL  PPLOT0  ;IF THERE IS STILL ANOTHER PLAYER THEN›                  ;LOOP AGAIN TO PLOT THE NEXT PLAYER›      RTS›;›;›MPLOT›      LDX  #3  ;LOAD X WITH THE MISSILE COUNT›      LDA  MISSILE   ;PLACE THE ADDRESS OF THE MISSILE TABLE›                   ;IN THE TEMPORARY ADDRESS REGISTER›      STA  ADD1›      LDA  MISSILE+1›      STA  ADD1+1›MPLOT0›      LDY  MOLDVERT,X ;GET THE OLD MISSILE LOCATION›      LDA  OFFTABLE,X ;TURN THE OLD IMAGE OFF›      AND  (ADD1),Y›      STA  (ADD1),Y›      LDY  MVERT,X  ;GET THE NEW MISSILE LOCATION›      LDA  ONTABLE,X  ;TURN THE NEW MISSILE IMAGE ON›      ORA  (ADD1),Y›      STA  (ADD1),Y›      TYA             ;MOVE THE NEW LOCATION TO THE OLD›                      ;MISSILE LOCATION TABLE FOR NEXT TIME›      STA  MOLDVERT,X›      DEX             ;DECREMENT THE MISSILE COUNTER›      BPL  MPLOT0     ;IF THERE IS STILL ANOTHER MISSILE›                   ;THEN LOOP TO PLOT THE NEXT MISSILE›      RTS›;›ONTABLE  DB $01,$0C,$20,$C0›OFFTABLE DB $FC,$F2,$CF,$2F›;›;›;  --------------------------------›;   DUMMY ROUTINE   (IGNORE)›;  --------------------------------›;›START›      JMP   ($0A)›      END   START›