The down arrow doesn't respond because of the overlay page number. Only when clicking a little bit left of the overlay, it will work.

I can't help but giggle at the fact that AI written project doesn't seem to get its home page right.

It's a kind of crappy slide deck, not a proper home page. Even worse, the link drops you into the middle of the deck. (TBF, it wouldn't be so bad if you know that it's a slide deck when you load the page.)

Try using the arrow keys to navigate. It took me multiple tries to get it figured out.

Use up/down to navigate within a chapter/topic. Use left/right to switch between topics.