{
 Star polygon tiling from cover of 
 "Tilings and Patterns: An Introduction"
 by Grunbaum & Shepard}

declare rad
rad:=1.5
declare side
side:=2*rad*sin(36)
declare perp
perp:=rad*cos(36)

sub bow(side)
declare ct
ct:=0
face(-90)
penDown
  loop
    forward(side)
    turn(72)
    ct:= ct+1
    exit if ct=5
  end loop
ct:=0
face(90)
  loop
    turn(72)
    forward(side)
    ct:= ct+1
    exit if ct=4
  end loop
end sub

sub vArrow(side)
declare ct
ct:=0
face(0)
penDown
  loop
    forward(side)
    turn(72)
    ct:= ct+1
    exit if ct=5
  end loop
ct:=0
face(180)
  loop
    turn(72)
    forward(side)
    ct:= ct+1
    exit if ct=4
  end loop
end sub

penUp
fork(6)
move((forkNumber-3)*(2*(rad+perp)+side),0)
fork(6)
move(0,(forkNumber-3)*(2*(rad+perp)+side))
fork(2)
move((forkNumber-1)*(rad+perp+side/2),(forkNumber-1)*(rad+perp+side/2))
bow(side)

penUp
move(-side/2,-rad-perp)
vArrow(side)