import turtle

wm = turtle.Screen()
wm.bgcolor("lightgreen")

tom = turtle.Turtle()

tom.shape("turtle")    # "arrow", "turtle", "circle", "square", "triangle", "classic"
tom.stamp()            # leave an impression on the canvas
tom.penup()

for i in range(12):
    tom.forward(100)
    tom.pendown()
    tom.forward(30)
    tom.penup()
    tom.forward(20)
    tom.stamp()
    tom.penup()
    tom.back(150)
    tom.left(360/12)

wm.mainloop()