box A;
box B [bottom=A@40%];
box C [bottom=A@20%];
box D [bottom=A@0%];
rightof A box E [top=A@60%];
box F [top=A@80%];
box G [top=A@100%];

arrows use draw_before=A;
(A, A@top)..(D,);
(A, A@bottom)..(D,);
