from tkinter import *
from random import *
import threading


root = Tk()
root.geometry('1000x750')
root.resizable(0, 0)
canvas = Canvas(width=1000, height=700, cursor='pencil')
canvas.pack()
canvas.create_oval(450, 350, 475, 375, width=5, fill='black')
canvas.update()
b1 = Button(root, text='Button')
b1.pack()

def random_move():
    x, y = randint(25, 50), randint(25, 50)
    h = 30
    z = 30

    while True:
        if x >= 900:
            break
        else:
            x += 1
        if y >= 900:
            break
        else:
            y += 1
        canvas.create_oval(x, y, h, z)


def start(event):
    b1.config(state='disabled')
    t1 = threading.Thread(target=random_move)
    t1.start()

b1.bind('<Button-1>', start)

root.mainloop()