import turtle
import random

def tree(n):
    
    
    if n >= 0:
        pen.pensize(n/10)
        angle = random.randint(0,30)
        length = random.randint(1,15)
        if n-length <= 12:
            pen.color("snow" or "lightcoral")
            pen.pensize(n/3)
        else:
            pen.color("sienna")
            pen.pensize(n/10)
        pen.forward(n)
        pen.right(angle)
        pen.down()
        tree(n-length)
        pen.up()
        pen.left(2*angle)
        pen.down()
        tree(n-length)
        pen.up()
        pen.right(angle)
        pen.backward(n)
pen = turtle.Turtle()
pen.speed(0)
pen.color('sienna')
# 画布大小
w = turtle.Screen()
w.bgcolor('wheat')      # wheat小麦

# 移动到起点
pen.left(90)
pen.up()
pen.backward(150)    # 后退
pen.down()
# pen.forward(100)
# pen.right(30)
# pen.forward(50)
# pen.up()
# pen.backward(50)
# pen.down()
# pen.left(60)
# pen.forward(50)
# pen.up()
# pen.backward(50)
# pen.right(30)
# pen.backward(100)
tree(60)



turtle.done()