用python3写一个弹弹球的小游戏（图形用户界面：tkinter）

from tkinter import *
from tkinter import messagebox
import random
import time
from PIL import Image, ImageTk
import sys


class Game:
    def __init__(self):
        self.tk = Tk()
        self.times = 0
        sw = self.tk.winfo_screenwidth()
        sh = self.tk.winfo_screenheight()
        image = Image.open(r'02.jpg')
        background_image = ImageTk.PhotoImage(image)
        ww = background_image.width()
        wh = background_image.height()
        x = (sw-ww)/2
        y = (sh-wh)/2
        self.tk.geometry("%dx%d+%d+%d" % (ww, wh, x, y))
        self.tk.title('欢迎进入弹弹弹')
        background_label = Label(self.tk, image=background_image)
        background_label.place(x=0, y=0, relwidth=1, relheight=1)
        self.tk.resizable(False, False)
        self.tk.wm_attributes("-topmost", 1)  # at top
        btn1 = Button(self.tk, text=