Tree:   Stick . (Branch)+
Branch: Stick . (Branch)+ | Stick . Leaves
Stick:  <model of a stick>
Leaves: <model of leaves>

##</code><code>##

Fighter: Body . Wing . Wing . Engine+
Body:    Fuselage . Cockpit . Weapon+
Wings:   (Control Surface) . Weapon? | Weapon?
Engine:  Intake? . Thruster . Exhaust
...