Hi,
I would like to obtain, if possible, a gray gradient like in the image. My
code uses Metapost but maybe this is possible with Metafun.
Thanks.
Fabrice

 \starttext
          \startMPcode
            u=1.2cm;
            interim ahangle := 30;

            z0=(0,0);
            z1=(3u,0);
            z2=(3u,4u);
            z3=(0,4u);
            z4=(0.8u,4u);
            z5=(2.2u,4u);

            path rectangle;
            rectangle=z0--z1--z2--z3--cycle;

            picture X;
            X = image(
            drawoptions(withpen pencircle scaled 1.25 withcolor
\MPcolor{orange});
            draw (left--right) scaled 2;
            draw (down--up) scaled 2;
            drawoptions();
            );

            fill z0--z4--z3--cycle withcolor .5[red,green];
            fill z1--z5--z2--cycle withcolor .5[red,green];
            fill z0--z4--z5--z1--cycle withcolor 0.625white;
            draw z0--z4--z3--cycle;
            draw z1--z5--z2--cycle;
            draw rectangle;

            path a[];
            a1 = subpath (0, 1) of rectangle shifted 10 down;
            a2 = subpath (3, 4) of rectangle shifted 10 left;
            a3 = subpath (2.26, 2.76) of rectangle shifted 13 up;

            drawdblarrow a1; label.bot("$30$", point 1/2 of a1);
            drawdblarrow a2; label.lft("$x+20$", point 1/2 of a2);
            drawdblarrow a3; label.top("$x$", point 1/2 of a3);

            draw X shifted z0;
            draw X shifted z1;
            draw X shifted z2;
            draw X shifted z3;
            draw X shifted z4;
            draw X shifted z5;

            label.ulft("B",z3);
            label.urt("C",z2);
            label.lrt("D",z1);
            label.llft("A",z0);
            label.top("E",z4);
            label.top("F",z5);
          \stopMPcode

 \stoptext