protected override void OnRenderFrame(FrameEventArgs e)
        {
            base.OnRenderFrame(e);

            GL.MatrixMode(All.Projection);
            GL.LoadIdentity();
            GL.Ortho(-1.0f, 1.0f, -1.5f, 1.5f, -1.0f, 1.0f);
            GL.MatrixMode(All.Modelview);
            GL.Rotate(3.0f, 0.0f, 0.0f, 1.0f);

            GL.ClearColor(0.5f, 0.5f, 0.5f, 1.0f);
            GL.Clear((uint)All.ColorBufferBit);

            GL.VertexPointer(2, All.Float, 0, square_vertices);
            GL.EnableClientState(All.VertexArray);
            GL.ColorPointer(4, All.UnsignedByte, 0, square_colors);
            GL.EnableClientState(All.ColorArray);

            GL.DrawArrays(All.TriangleStrip, 0, 4);

            SwapBuffers();
        }

        float[] square_vertices = {
            -0.5f, -0.5f,
            0.5f, -0.5f,
            -0.5f, 0.5f,
            0.5f, 0.5f,
        };

        byte[] square_colors = {
            255, 255,   0, 255,
            0,   255, 255, 255,
            0,     0,    0,  0,
            255,   0,  255, 255,
        };