Right now there’s a lot of interest in interactive magic tricks, where someone can follow along from their home, and the magic happens to them. There a principle that I was first introduced to in the trick Fingertip Mentalism from the book Nothing But Mystery by Jim Steinmeyer. Then I found the book Body Mentalism by Juan Pablo explains and explores the principle much more in depth.
Here’s a video I recently made using the principle:
Personally I like the idea of having people post a pic in the comments much more interactive than simply revealing where they are. Also I find a lot of humor in them posting their middle finger, but in my soul, I’m still a 12 year old boy.
Once you know how to do the math, it’s something that you can do anytime. What I like about it is the principle isn’t limited to “do as I do” type tricks. It’s handy to know things like this, it allows you to do some impromptu magic when you have nothing!