program scrolly;
uses
  c64_vic;

const
  SCREEN0_ADDRESS = 1024;
  SCREEN_WIDTH    = 40;
  row             = 15;

  scroll_text : String = 'this is a simple scroller demo written in pascal and compiled using pas6502 into 6502 assembly code.  as you can see, you don''t need pure assembly to do simple effects like this.                                       ';

  logo : array[0..1000 - 1] of Byte = (
  32,224,224,224,224,32,224,224,224,224,32,224,224,224,32,224,224,224,224,224,32,224,224,224,224,224,32,224,224,224,224,224,32,96,224,224,224,96,32,32,
  32,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,32,224,224,224,224,224,224,224,224,224,224,224,32,32,
  32,224,224,32,224,224,224,224,32,224,224,224,224,32,32,224,224,32,32,32,32,224,224,32,32,32,32,224,224,32,96,224,224,32,224,32,32,224,224,96,
  32,224,224,224,224,224,224,224,224,224,224,224,224,224,32,224,224,224,224,224,32,224,224,224,224,224,32,224,224,32,96,224,224,96,224,224,224,224,224,96,
  32,224,224,224,224,224,224,224,224,224,224,96,96,224,224,224,224,224,224,224,224,32,224,224,224,224,224,224,224,32,32,224,224,224,224,224,224,224,224,96,
  32,224,224,32,32,96,224,224,96,224,224,32,96,224,224,224,224,32,32,224,224,32,32,32,96,224,224,224,224,32,32,224,224,224,224,32,32,32,32,96,
  32,224,224,32,32,96,224,224,96,224,224,32,32,224,224,224,224,32,32,224,224,32,32,32,96,224,224,224,224,32,32,224,224,224,224,32,32,32,32,32,
  32,224,224,32,32,96,224,224,32,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,224,32,32,
  32,96,224,32,32,96,32,224,32,32,224,32,224,224,224,32,224,224,224,224,224,32,224,224,224,224,224,32,224,224,224,224,224,32,224,224,224,224,224,32,
  32,32,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,96,
  32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,
  32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,
  32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,
  67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,
  32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,
  32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,
  32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,
  67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,67,
  32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,
  32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,
  32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,
  32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,
  32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,
  32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,
  32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32
  );

  logo_colours : array[0..1000 - 1] of Byte = (
  14,10,10,10,10,14,10,10,10,10,14,10,10,10,14,1,1,1,1,1,14,1,1,1,1,1,14,1,1,1,1,1,14,1,1,1,1,1,14,14,
  14,10,0,0,10,0,10,0,0,10,0,10,0,0,0,1,0,0,0,0,0,1,0,0,0,1,14,1,0,0,1,1,0,1,0,0,0,1,14,14,
  14,10,0,14,10,0,10,0,14,10,0,10,0,14,14,1,0,14,14,14,14,1,0,14,14,14,14,1,0,14,1,1,0,14,0,14,14,1,0,10,
  14,10,10,10,10,0,10,10,10,10,0,10,10,10,14,1,1,1,1,1,14,1,1,1,1,1,14,1,0,14,1,1,0,1,1,1,1,1,0,10,
  14,10,0,0,0,0,10,0,0,10,0,10,0,10,0,1,0,0,0,1,0,14,0,0,0,1,0,1,0,14,14,1,0,1,0,0,0,0,0,10,
  14,10,0,14,14,0,10,0,0,10,0,14,0,10,0,1,0,14,14,1,0,14,14,14,1,1,0,1,0,14,14,1,0,1,0,14,14,14,14,10,
  14,10,0,14,14,10,10,0,0,10,0,14,14,10,0,1,0,14,14,1,0,14,14,14,1,1,0,1,0,14,14,1,0,1,0,14,14,14,14,14,
  14,10,0,14,14,10,10,0,14,10,0,10,10,10,0,1,1,1,1,1,0,1,1,1,1,1,0,1,1,1,1,1,0,1,1,1,1,1,14,14,
  14,10,0,14,14,10,14,0,14,14,0,14,0,0,0,14,0,0,0,0,0,14,0,0,0,0,0,14,0,0,0,0,0,14,0,0,0,0,0,14,
  14,14,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
  14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,
  14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,
  14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,
  10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
  14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,
  14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,
  14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,
  10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
  14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,
  14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,
  14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,
  14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,
  14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,
  14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,
  14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14
);

var
  i              : Byte;
  screen         : Byte absolute SCREEN0_ADDRESS;
  color          : Byte absolute $d800;
  letter_index   : Byte;

procedure stabilize(x : byte); assembler;
asm
!:
burn:
  dex
  bne burn
end;

procedure initScreen;
begin
  for i := 0 to 250 do begin
    screen[i+000] := logo[i+000];
    screen[i+250] := logo[i+250];
    screen[i+500] := logo[i+500];
    screen[i+750] := logo[i+750];
    color[i+000] := logo_colours[i+000];
    color[i+250] := logo_colours[i+250];
    color[i+500] := logo_colours[i+500];
    color[i+750] := logo_colours[i+750];
  end;

  vic.bg_color0 := medium_grey;
  vic.border    := light_grey;
end;

procedure hardscroll;
var
  i : Byte;
begin
  for i := 0 to SCREEN_WIDTH - 1 do begin
    screen[SCREEN_WIDTH*row+i] := screen[SCREEN_WIDTH*row + 1+i];
    color[SCREEN_WIDTH*row+i]  := color[SCREEN_WIDTH*row + 1+i];
  end;

  screen[SCREEN_WIDTH * row + 39] := scroll_text[letter_index];
  color[SCREEN_WIDTH * row + 39] := vic.border;

  letter_index := letter_index + 1;
  if letter_index > length(scroll_text) then letter_index := 1;
end;

procedure mainLoop;
var
  scroll : Byte;
begin
  scroll := 7;

  while true do begin
    vic_waitForRaster(row * 8 - 1 + 50);
    stabilize(8);
    vic_38_columns();
    vic_set_scroll(scroll and 7,3);

    vic_waitForRaster(row * 8 + 7 + 50);

    stabilize(23);
    vic_40_columns();
    vic_set_scroll(0,3);
    if scroll = 0 then begin
      scroll := 7;
      hardscroll();
    end else begin
      scroll := scroll - 1;
    end;
  end;
end;

begin
  letter_index := 1;
  disable_irq;
  initScreen;

  mainLoop;
end.