Adding interaction based on the mouse button being pressed

my_first_game_mouse_down.py

import random

WIDTH = 600
HEIGHT = 400

alien = Actor('alien', midbottom=(100,200))

def draw():
    screen.fill((240, 6, 253))
    alien.draw()
    
def update():
    alien.left += 5
    if alien.left > WIDTH:
        alien.topright = 0, random.randint(25, 375)
        
def on_mouse_down(pos):
    if alien.collidepoint(pos):
        print("you hit me!")
    else:
        print("you missed me!")