box A;
box B [mbottom=A@m40%];
box C [mbottom=A@m20%];
box D [mbottom=A@m0%];
rightof A box E [mtop=A@m60%];
box F [mtop=A@m80%];
box G [mtop=A@m100%];

arrows use draw_before=A;
(A, A@mtop)..(D,);
(A, A@mbottom)..(D,);
