from graphics import *

def main():
    w = GraphWin("Target",800,600)
    w.setBackground("lightyellow")

    r = 200
    for i in range(10):
        C = Circle(Point(400,300),r-20*i)
        if i%2 == 1:
            C.setFill("white")
        else:
            C.setFill("black")
        C.draw(w)

    w.getMouse()
    w.close()

main()