from turtle import *
from random import random


penup()
speed(0)
left(90)
backward(300)
pendown()

def arbrec(n,l,th,c=0):
    if n == 0 :
        forward(l/3)
        backward(l/3)
    else :
        tr = (random() - .5)/2 #Angles modifies entre -25 % et 25 %
        tr1 = (random() - .5)/2
        lr = (random()-.25)*2/3 # Longueurs modifiees entre -17% et + 50%
        lr1 = (random()-0.25)*2/3
        pensize(5*n/(c+n))
        tup = (0.5,0.3+0.7*(c-n)/(c+n),0)
        pencolor(tup)
        forward(l/3)
        right(th)
        arbrec(n-1,2*l*(1+lr)/3,th*(1+tr),c+1)
        left(2*th)
        arbrec(n-1,2*l*(1+lr1)/3,th*(1+tr1),c+1)
        right(th)
        penup()
        backward(l/3)
        pendown()

arbrec(8,300,25,5)