import turtle

wn = turtle.Screen()                # create window for turtle t1 to draw
wn.bgcolor("black")                 # set background color of the window

t1 = turtle.Turtle()
t1.shape("classic")

t1.color("yellow")
t1.width(3)

for i in range(20):
    t1.forward(i * 10)
    t1.right(90)

wn.mainloop()           # wait for user to close the window