import turtle
a = turtle.Pen()
b = turtle.Pen()
c = turtle.Pen()
d = turtle.Pen()
b.left(90)
c.left(180)
d.left(270)
x = 20
y = 90

while True:
    x *= 2
    for i in (a, b, c, d):
        i.forward(x)
        i.right(y)