    ntColour = const(.8),
    h = const(3/2 * sqrt(3)),
  
    line = { polyline((-1.5,0),(-.5,0),(0,-cos(30)),(.5,0),(1.5,0)) },
    
    r1 = scale(1/3) . translate(-1,0),
    r2 = translate(1.5,0) . scale(1/3) . rotate(-60) . translate(-.5,0),
    r3 = translate(-1.5,0) . scale(1/3) . rotate(60) . translate(.5,0),
    r4 = scale(1/3) . translate(1,0),
    refine = < r1, r2, r3, r4 >,
    
    t1 = translate(-1.5,0) . rotate(-60) . translate(0,-2 * cos(30)),
    t2 = translate(1.5,0) . rotate(60) . translate(0,-2 * cos(30)),
    t3 = rotate(180) . translate(0,cos(30)),
    t = <t1, t2, t3>,
    
    c1 = scale(1/3) . translate(0,4/3 * cos(30)),
    c2 = use(c1) . rotate(60),
    c3 = use(c1) . rotate(120),
    c4 = use(c1) . rotate(180),
    c5 = use(c1) . rotate(240),
    c6 = use(c1) . rotate(300),
    c7 = rotate(30) . scale(sqrt(3)/3),
    c = <c1, c2, c3, c4, c5, c6, c7>,
