"Yes I do. It's an interesting story. I was wondering the same thing myself one night when I was up. I never sleep, you see. So anyway I was up and I wanted to figure out how it worked, so I took it apart. At first all I saw was a bunch of lenses and stuff but then I remembered that when you play Duck Hunt, or other games, the whole screen changes color when you press the trigger. I figured it had to have something to do with color.
So anyway, basically what happens is that the gun sees a very small part of the screen, and it recieves color from it, which is why the Zapper won't work on a screen whose color or contrast levels are way off. The gun tells the nintendo what color it sees, and the nintendo then knows what you shot.
And they are pretty easy to put together, in fact, I might be able to whip you up a custom job if you want. I need something fun to do anyway, because once you figure out how something works, you really don't have an excuse to take it apart anymore, but if you want to build another one you HAVE to take it apart again, which is fun. So anyway, I wouldn't mind doing that for you, but it might take awhile as I have some other projects to do."
-Hyper-kinetic Engineering Student Jordan Cochran
found here