You know what would make for a really cool demonstration? You know in a restaurant where some show-off manages to pull the tablecloth off the table without taking any of the dishes with it? That would make for a really cool demonstration. However, That is terribly impractical for a lecture setting, so instead we have this much smaller, automated version of that! Just pull the metal lever back and release it and it will knock the card aside without disturbing the ball at all.