Several people have asked me how I made those videos in which I walk behind the screen and in front of the screen (See linked videos "April Fools: Math Class Shadow" and "2009 Halloween Math Class"). This video is a "how-to" video that describes the process. Here's the equipment a former student, Andrew Staver, and I used: a Panasonic miniDV camcorder (although the newer models would be better),
![How to Make Videos that Mix Live Action with Video - Brief Tutorial](https://cdn-ak-scissors.b.st-hatena.com/image/square/e586d30a7259cfd367ee4c4004324b214e6a6cca/height=288;version=1;width=512/https%3A%2F%2Fi.ytimg.com%2Fvi%2FixSCjigDeM8%2Fhqdefault.jpg)