uses GraphABC; 

procedure RLine(x, y, x1, y1: real):=Line(Round(x), Round(y), Round(x1), Round(y1));

procedure Draw(x, y, l: real);
begin
  var xp := x + l;
  var xm := x - l;
  var yp := y + l;
  var ym := y - l;
  
  RLine(x, y, xp, y);
  RLine(x, y, xm, y);
  RLine(xp, y, xp, ym);
  RLine(xp, y, xp, yp);
  RLine(xm, y, xm, ym);
  RLine(xm, y, xm, yp);
  
  if l > 10 then
  begin
    l := l / 2; 
    Draw(xp, ym, l); 
    Draw(xp, yp, l); 
    Draw(xm, ym, l); 
    Draw(xm, yp, l); 
  end; 
end;

begin
  LockDrawing();
  Draw(Window.Width / 2, Window.Height / 2, 100);
  Redraw();
end.