This is the general framework for the bouncing ball idea (modeled after the DVD logo bouncing in a room and everyone waiting for it to hit the edge).
def main():
canvas = Canvas(CANVAS_WIDTH, CANVAS_HEIGHT, ‘DVD’)
dvd = canvas.create_oval(. . .)
change_x = 1 # start with these initial velocities
change_y = 1
while True:
canvas.move(dvd, change_x, change_y)
if # we hit the top or bottom:
change_y = -change_y
elif # we hit the left or right:
change_x = -change_x
canvas.update()
time.sleep(DELAY)