private void Rekursionen_MouseDown(object sender, MouseEventArgs e)
        {
            if (m_tbhohe.Text.Length > 0 && m_tbbreite.Text.Length > 0)
            {
                lange = int.Parse(m_tbhohe.Text);
                breite = int.Parse(m_tbbreite.Text);
            }

            m_mitte = new Point(e.X, e.Y);

            m_graph.DrawLine(m_rec, m_mitte.X - 2, m_mitte.Y - 2, m_mitte.X + 2, m_mitte.Y + 2);
            m_graph.DrawLine(m_rec, m_mitte.X - 2, m_mitte.Y + 2, m_mitte.X + 2, m_mitte.Y - 2);
            Muster(m_mitte, lange, breite);
        }

        private void Muster(Point p, int a, int b)
        {
            m_graph.DrawRectangle(m_rec, p.X - a/2, p.Y - b/2 , a, b);
            Point mittelinks = new Point(p.X - a / 2, p.Y);
            Point mitterechts = new Point(p.X + a / 2, p.Y);
            m_graph.DrawEllipse(m_pell, mittelinks.X - a / 4, mittelinks.Y - a / 4, a / 2, a / 2);
            m_graph.DrawEllipse(m_pell, mitterechts.X - a / 4, mitterechts.Y - a / 4, a / 2, a / 2);
            m_graph.FillEllipse(m_bell, mittelinks.X - a / 4, mittelinks.Y - a / 4, a / 2, a / 2);
            m_graph.FillEllipse(m_bell, mitterechts.X - a / 4, mitterechts.Y - a / 4, a / 2, a / 2);

            if (b >= 10 || a >= 10)
            {
                Thread.Sleep(100);
                Muster(mittelinks, a /2, b/2);
                Muster(mitterechts, a/2, b/2);
            }
        }