D2. Take 4 black struts and put 2 black
struts on either side of the red strut, and
connect to the blue hubs at the top of the
dome.
D3. Take 4 blue struts and connect to the
two blue hubs at the top of the dome.
D4. Take 6 blue struts and connect them so
that they point to the center of the tunnel
dome.