u = 2cm;

color c[];
c1 := (0,0.6,0.8);
c2 := (0.8,0.6,0);

vardef cercles (expr x,y,c)  =
    for i:=1 upto 4: 
        draw fullcircle  scaled ((2+i)*u) shifted (x,y) 
             withpen pencircle scaled .15u withcolor c;
    endfor;
enddef;


path ecran;
ecran := (0,0) .. (4u,-0.9u) .. (8u,0) .. 
         (8.9u,4u) .. (8u,8u) .. (4u,8.9u) .. 
         (0,8u) .. (-0.9u,4u) .. cycle;

picture sauvegarde;

beginfig(1);

    cercles(0,0,c2);
    cercles(0,8u,c2);
    cercles(8u,8u,c2);
    cercles(8u,0,c2);

    clip currentpicture to ecran;
    sauvegarde := currentpicture;
    currentpicture := nullpicture;

    cercles(0,0,c1);
    cercles(0,8u,c1);
    cercles(8u,8u,c1);
    cercles(8u,0,c1);

    draw sauvegarde;

endfig;

beginfig(2);

    cercles(0,0,c2);
    cercles(0,8u,c2);
    cercles(8u,8u,c2);
    cercles(8u,0,c2);

    clip currentpicture to ecran;

endfig;

end