I don’t know if you have ever trained a parrot to talk, I haven’t, but my late grand father Pop Dyker had, and he gave me this tip.
“You put a cover over the cage so there’s nothing to look at and the little bugger has listen to you.”
When controlling your PowerPoint presentation the most important item is not your mouse, it is the ‘b’ key on your keyboard.
This blanks the screen “so there’s nothing to look”. It alters the lighting in the room. The whole ambiance of the room changes. Even ‘Facebook Freddie’ in the back row will look up (if only momentarily).
It’s a useful trick when you have a key point to emphasize.