function - create_circle

def main():
    radius = 20
    diameter = 2 * radius
    v_distance_between_ball_centers = 100
    bottom_ball_initial_y = 500
    x_ball_center = 250
    win = GraphWin('Animation', 600, 600, autoflush=False)

    c1_center = Point(x_ball_center, bottom_ball_initial_y)
    c1 = Circle(c1_center, radius)
    c1.setFill('blue')
    c1.draw(win)