*       =       $c000

SetCursor  =  $E50C     ;x=numero riga, y=numero colonna
PrintString = $AB1E     ;A con il Byte Basso e il registro Y con il Byte Alto dell’indirizzo
ZP      =       $fb
ZP2=ZP+1

        lda     #$18
        sta     ZP2
        ldx     #0

mainloop
        ldy     #0
        jsr     SetCursor
        jsr     PrintRow
        inx
        dec     ZP2
        bne     mainloop
        jmp     WaitForSpace

PrintRow
        stx     ZP
        lda     #<Balls
        ldy     #>Balls
        jsr     PrintString
        ldx     ZP
        rts

;==============================================================================
; Wait for Space bar to be pressed
;==============================================================================

WaitForSpace
        lda     #$7f    ;%01111111 - only row 7 KB matrix
        sta     $dc00
        lda     $dc01
        and     #$10    ;mask %00010000
        bne     WaitForSpace

        rts
Balls
        text "QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ"
        byte 0