from turtle import *
from random import *
from math import *
def tree(n,l):
pd()#下笔
#阴影效果
t = cos(radians(heading()+45))/8+0.25
pencolor(t,t,t)
pensize(n/3)
forward(l)#画树枝
if n>0:
b = random()*15+10 #右分支偏转角度
c = random()*15+10 #左分支偏转角度
d = l*(random()*0.25+0.7) #下一个分支的长度
#右转一定角度,画右分支
right(b)
tree(n-1,d)
#左转一定角度，画左分支
left(b+c)
tree(n-1,d)
#转回来
right(c)
else:
#画叶子
right(90)
n=cos(radians(heading()-45))/4+0.5
pencolor(n,n*0.8,n*0.8)
circle(3)
left(90)
#添加0.3倍的飘落叶子
if(random()>0.7):
pu()
#飘落
t = heading()
an = -40 +random()*40
setheading(an)
dis = int(800*random()*0.5 + 400*random()*0.3 + 200*random()*0.2)
forward(dis)
setheading(t)
#画叶子
pd()
right(90)
n = cos(radians(heading()-45))/4+0.5
pencolor(n*0.5+0.5,0.4+n*0.4,0.4+n*0.4)
circle(2)
left(90)
pu()
#返回
t=heading()
setheading(an)
backward(dis)
setheading(t)
pu()
backward(l)#退回
bgcolor(0.5,0.5,0.5)#背景色
ht()#隐藏turtle
speed(0)#速度 1-10渐进，0 最快
tracer(0,0)
pu()#抬笔
backward(100)
left(90)#左转90度
pu()#抬笔
backward(300)#后退300
tree(12,100)#递归7层
done()
