unit Unit1;

{$mode objfpc}{$H+}

interface

uses

  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, ExtCtrls;

type

  { TForm1 }

  TForm1 = class(TForm)

    Timer1: TTimer;

    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);

    procedure FormPaint(Sender: TObject);

    procedure Timer1Timer(Sender: TObject);

  private

    { private declarations }

  public

    { public declarations }

  end;

const

  maxLen = 50;

var

  Form1: TForm1;

  pos: integer = 0;

  len: integer = 0;

  px: array[0..maxLen] of integer;

  py: array[0..maxLen] of integer;

implementation

{$R *.lfm}

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,

  Y: Integer);

begin

  pos := pos + 1;

  len := len + 1;

  if pos >= maxLen then pos := 0;

  if len > maxLen then len := maxLen;

  px[pos] := x;

  py[pos] := y;

end;

procedure TForm1.Timer1Timer(Sender: TObject);

begin

  Refresh;

  len := len - 1;

  if len < 0 then len := 0;

end;

procedure TForm1.FormPaint(Sender: TObject);

var

  i, p: Integer;

begin

  Canvas.MoveTo(px[pos], py[pos]);

  for i := 0 to len-1 do begin

    p := (maxLen + pos - i) mod maxLen;

    Canvas.Pen.Width := len - i;

    Canvas.LineTo(px[p], py[p]);

  end;

end;

end.