#2.8 DrawSquareHelix.py

#2.8 DrawSquareHelix.py
#coding = utf-8
import turtle
def DrawSquareHelix(lenth,gap):
	angle=[90,180,270,0]
	lenths=[lenth,lenth,lenth+gap,lenth+gap]
	for i in range(4):
		turtle.seth(angle[i])
		turtle.fd(lenths[i])

N=10
turtle.penup()
turtle.setup(1600,800,0,0)
turtle.fd(-400)
turtle.pendown()
for i in range(N):
	DrawSquareHelix(10+i*20,10)

turtle.penup()
turtle.seth(0)
turtle.fd(800)
turtle.seth(90)
turtle.fd(N*10)
turtle.pendown()

def DrawSquareHelixLittle(lenth,angle):
	changeangle=[0,90]
	for i in range(2):
		turtle.seth(angle+changeangle[i])
		turtle.fd(lenth)

angle=90
for i in range(20):
	DrawSquareHelixLittle(10+i*10,angle)
	angle+=180
turtle.done()