// examples from: http://www.joostrekveld.net/?page_id=117

X>F
F>F[+F]F[-F]

forward 8
angle 25.5
branch thickness 4
branch scaling .6

X>F
F>F[+F]F[-F][F]

forward 9
angle 20
branch thickness 3
branch scaling .75

X>F[+X][-X]FX
F>FF

forward 5
angle 25.5
branch thickness 2
branch scaling 0.8

X>F[+X]F[-X]+X
F>FF

forward 5
angle 20
branch thickness 2
branch scaling 0.75