Два падающих квадрата

import tkinter as tk
from tkinter import Canvas
import random
 
 
def isin(x: int, y: list):
    for i in y:
        if i == x:
            return True
        return False
 
 
def fall_1():
    b1 = random.randrange(0, 650, 50)
    figure_1 = canvas.create_rectangle(b1, 0, b1 + 100, 100, fill="red")
    canvas.move(figure_1, 0, 1)
    if isin(b1, forbid):
        if canvas.coords(figure_1)[1] != 450:
            root.after(2, fall_1)
    else:
        if canvas.coords(figure_1)[1] != 550:
            root.after(2, fall_1)
 
 
def fall():
    canvas.move(figure, 0, 1)
    if canvas.coords(figure)[1] != 550:
        root.after(2, fall)
    elif canvas.coords(figure) == 550:
         fall_1()
 
 
b = random.randrange(0, 650, 50)
forbid = []
for i in range(b - 100, b + 100):
    forbid.append(i)
 
root = tk.Tk()
root.title("Квадраты")
root.resizable(False, False)
root.geometry("1078x800")
canvas = Canvas(width=1079,
                height=650,
                bg="blue")
figure = canvas.create_rectangle(b, 0, b + 100, 100, fill="red")
fall()
canvas.grid()
root.mainloop()

    elif canvas.coords(figure)[1] == 550: