Python 3 / pygame / Создание игры Arkanoid⁠⁠

Нужна подсказка как сделать код отскакивания мячика

Вот код:

from tkinter import *

def roll():

global ball_y

global dy

global ball_x

global dx

global platform

ball_x = ball_x + dx

if ball_x > 700 or ball_x < 0:

dx = -dx

ball_y = ball_y + dy

if ball_y > 500 or ball_y < 0:

dy = -dy

canv.coords(ball, ball_x, ball_y, ball_x+100, ball_y+100,)

form.after(10,roll)

def pad_move(event):

global pad_x

pad_x = event.x

canv.coords(platform, pad_x-50, 500, pad_x+50, 530)

form = Tk()

form.title("Arkanoid TEST")

form.geometry("800x600")

canv = Canvas(form, width = 800, height = 600, bg="lightblue")

canv.pack()

ball_x=0

ball_y=0

dx = 5

dy = 5

ball = canv.create_oval(ball_x, ball_y, ball_x+100, ball_y+100, fill = "Black")

form.after(0,roll)

pad_x = 150

platform = canv.create_rectangle(pad_x, 500,pad_x+100, 530, fill = "Black")

form.bind("<Motion>", pad_move)

form.mainloop()