size(0,25cm); guide center=(0,1){W}..tension 0.8..(0,0){(1,-.5)}..tension 0.8..{W}(0,-1); draw((0,1)..(-1,0)..(0,-1)); filldraw(center{E}..{N}(1,0)..{W}cycle); unfill(circle((0,0.5),0.125)); fill(circle((0,-0.5),0.125));