procedure TForm1.Button1Click(Sender: TObject);
begin
  button1.Visible:=False;
  button1.Enabled:=False;
  button2.Enabled:=True;
  button2.Visible:=True;
  button3.Enabled:=False;
  button3.Visible:=True;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  button1.Visible:=True;
  button1.Enabled:=False;
  button2.Enabled:=False;
  button2.Visible:=False;
  button3.Enabled:=True;
  button3.Visible:=True;
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
  button1.Visible:=True;
  button1.Enabled:=True;
  button2.Enabled:=False;
  button2.Visible:=True;
  button3.Enabled:=False;
  button3.Visible:=False;
end;