hwork.asm

;*******************************************************************************
;*                                                                             *
;*   long branch never - Episode 03 Homework                                   *
;*   https://www.youtube.com/watch?v=6DldT2rH63c                               *
;*                                                                             *
;*   Jason Pittman                                                             *
;*                                                                             *
;*******************************************************************************

            org     $4000

Start       lda     #$20            ; Load char ' ' into A register
            ldx     #$400           ; point X-register beginning of video space
Loop        sta     ,x+             ; put value A-register on screen, increment
            cmpx    #$600           ; are we at end of video screen?
            bne     Loop            ; no? go back to do more

            ldx     #Line1
            ldy     #$424
            bsr     WriteDark       ; use bsr to return from WriteDark?

            ldx     #Line2          ; write another line
            ldy     #$444
            bsr     WriteDark
            
            ldx     #Line3
            ldy     #$465
            bsr     WriteDark
            
            ldx     #Line4
            ldy     #$4a8
            bsr     WriteDark

            bra     Footer
            
WriteDark   lda     ,x+
            cmpa    #64
            lbeq    Done
            blt     Skip            ; if char is > 64, subtract 64 to make black BG
            suba    #64             ; TODO: dont subtract if > end of char set so
                                    ; it doesn't foul up those block character things

Skip        sta     ,y+
            bra     WriteDark
            
            lda     #$FF            ; Load char ' ' into A register
Footer      
            sta     $501
            sta     $505
            sta     $508
            sta     $509
            sta     $50d
            sta     $50e
            sta     $511
            sta     $512
            sta     $515
            sta     $517
            sta     $518
            sta     $519
            sta     $51a
            sta     $51b
            sta     $51e
            
            sta     $521
            sta     $525
            sta     $527
            sta     $52a
            sta     $52c
            sta     $52f
            sta     $531
            sta     $533
            sta     $535
            sta     $537
            sta     $53b
            sta     $53e
            
            sta     $541
            sta     $545
            sta     $547
            sta     $54a
            sta     $54c
            sta     $54f
            sta     $551
            sta     $554
            sta     $555
            sta     $557
            sta     $55e
            
            sta     $561
            sta     $563
            sta     $565
            sta     $567
            sta     $568
            sta     $569
            sta     $56a
            sta     $56c
            sta     $56f
            sta     $571
            sta     $575
            sta     $577
            sta     $57a
            sta     $57b
            sta     $57c
            sta     $57e
            
            sta     $581
            sta     $583
            sta     $585
            sta     $587
            sta     $589
            sta     $58c
            sta     $58f
            sta     $591
            sta     $595
            sta     $597
            sta     $59b
            
            sta     $5a2
            sta     $5a4
            sta     $5a7
            sta     $5aa
            sta     $5ad
            sta     $5ae
            sta     $5b1
            sta     $5b5
            sta     $5b7
            sta     $5b8
            sta     $5b9
            sta     $5ba
            sta     $5bb
            sta     $5be
            
            deca
            lbra     Footer         ; had to change bra to lbra to prevent 
                                    ; Byte overflow     ¯\_(ツ)_/¯

Line1       fcc     'YOU WOULD THINK THAT YOU@'
Line2       fcc     "WOULD JUST TYPE '72' AND@"
Line3       fcc     'YOU WOULD BE ALL SET.@'
Line4       fcc     'YOU WOULD BE...@'

Done        
            rts

            End     Start