If you google fling-ama-string, you'll get lots of you tube videos showing it in action. I have one for Muffs and Abby. They like it, but it's one of those toys I bring out every few months for a few days and then put back into storage, in part because I find they like it when they haven't seen it for a while, but then they get tired of it.
One word of advice...when it's attached to the door and turned on, make sure the door is closed. Using it on an open door could risk injury to the cats. Failing that, it could also risk injury to your door, or your walls.