Watch the video all the way through.
What do you see?
Watch it again as many times as you like. (You can pause it at any point.)
Describe what you notice.
How many vertical lines are there at the start?
How many vertical lines are there at the end?
Which lines 'fall into' others?
Focus on the starting image.
How would you add to the picture to continue the pattern?
What would happen if you could watch an animation using your new image at the start?