File:Чёртова лестница.png

uses GraphABC; 

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

function Distance(x, y, x1, y1: real):= Sqrt(Sqr(x1 - x) + Sqr(y1 - y)); 

procedure Draw(x, y, x1, y1: real);
begin
  var dx := (x1 - x) / 3;
  var my := (y1 + y) / 2; 
  
  RLine(x + dx, my, x + 2 * dx, my);
  var x2 := x + 2 * dx;
  
  if Distance(x, y, x1, y1) < 10 then 
  begin
    RLine(x, y, x + dx, my); 
    RLine(x2, my, x1, y1); 
  end 
  else 
  begin
    Draw(x, y, x + dx, my); 
    Draw(x2, my, x1, y1); 
  end; 
end;

begin
  SetWindowIsFixedSize(true);
  
  var W := Window.Width; 
  var H := Window.Height;
  
  SetSmoothingOff();
  
  LockDrawing();
  Draw(0, H, W, 0); 
  FloodFill(W - 1, H - 1, clBlack);
  Redraw();
end.