Simple 'Space Invaders' with python 3 and Turtle

Very simple game based on Space Invaders using Python 3 and the Turtle module.
I am trying to make it as easy as possible to teach my kids.
Feel free to look at the code below.

# out the code for gif images for the player and enemies for the code to work with the built in shapes. (You need to add the gif files to the same directory.) See Line 25, 26, 60 and 101

My link to game with added shields:

I also played with the gif animation of the aliens:

See the youtube tutorial by Christian Thompson!!