protected override void OnRenderFrame(FrameEventArgs e)
        {
            GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);
            GL.Enable(EnableCap.Blend);

            GL.BlendFunc(BlendingFactorSrc.One, BlendingFactorDest.DstAlpha);
            GL.MatrixMode(MatrixMode.Modelview);
            GL.LoadIdentity();

            g2d.BeginRender();

            // g2d.Graphics.FillEllipse(new SolidBrush(Color.Red), 400, 700, 50, 50);
            // g2d.Graphics.DrawPolygon(new Pen(Color.Green, 4), new Point[]
            // {
            //     new Point(400, 100), new Point(450, 200),
            //     new Point(300, 400), new Point(150, 150)
            // });
            FactoryScreen.Draw();


            g2d.EndRender();

            SwapBuffers();
        }