matrix falling code sim

matrix.pas

program matrix;

uses
  graph,
  SysUtils;

const
  colnum = 15;
var
  GrDriver, GrMode, GrError: smallint;
  randomChars: ansistring;
  headPlace: array [0..1000] of integer;
  counter, counter2, curRand, curCol: integer;
  charx, chary, maxx, maxy, charlen, charheight: integer;
begin
  randomize();
  // graph init
  GrDriver := Detect;
  InitGraph(GrDriver, GrMode, '');
  GrError := GraphResult;
  if GrError <> GrOK then
  begin
    Writeln('Zª_Ù”  Òì_ § ÒØ”Р£ì ä_”_.');
    Writeln(GraphErrorMsg(GrError));
    Halt;
  end;
  maxx := getmaxx;
  maxy := getmaxy;

  //text style
  SetTextStyle(smallFont, 0, 2);
  SetTextJustify(righttext, bottomText);

  //pallete
  SetRGBPalette(1, 255, 255, 255);
  SetRGBPalette(2, 150, 255, 150);
  SetRGBPalette(3, 100, 205, 100);
  SetRGBPalette(4, 0, 100, 0);
  SetRGBPalette(5, 0, 100, 0);
  SetRGBPalette(6, 0, 100, 0);
  SetRGBPalette(7, 0, 100, 0);
  SetRGBPalette(8, 0, 100, 0);
  SetRGBPalette(9, 0, 100, 0);
  SetRGBPalette(10, 0, 100, 0);
  SetRGBPalette(11, 0, 100, 0);
  SetRGBPalette(12, 0, 50, 0);
  SetRGBPalette(13, 0, 25, 0);
  SetRGBPalette(14, 0, 0, 0);
  SetRGBPalette(15, 0, 0, 0);

  charlen := (TextWidth('A'));
  charheight := (TextHeight('A'));
  charx := round(maxx / charlen);
  chary := round(maxy / charheight);

  setlength(randomchars,charx*chary);

  randomchars := '';
  for counter := 1 to charx * chary do
    randomchars := randomchars + chr(random(94) + 32);

  for counter := 1 to charx do
    headPlace[counter] := 0;

  headPlace[0] := 1;

  while True do
  begin
    if random(20) = 1 then
      curRand := random(charx) + 1
    else
      currand := 0;
    if headplace[currand] = 0 then
      headplace[currand] := 1;
    for counter := 1 to charx do
    begin
      counter2 := headplace[counter];
      curCol := 1;
      if (random(10) = 1) then
      begin
        while (counter2 > 0) and (curcol < colnum) do
        begin
          setcolor(curCol);
          if (counter2<=chary) then
          outtextxy(counter * charlen, counter2 * charheight,
            randomchars[counter * counter2]);
          Inc(curcol);
          Dec(counter2);
        end;
        if headplace[counter] > 0 then
          Inc(headplace[counter]);
        if headplace[counter] - colnum > chary then
          headplace[counter] := 0;
      end;
    end;
  end;

  writeln(randomchars);
  readln;
end.