Excellent ... this was the motivation for my question. I'm actually planning one very similar. I currently have about 20 stages planned. The downside is there is no way (that I know of) to hide a cache on geocaching.com since many of the puzzles will be take-home.
Do you know if there is a way to hide caches until a password or decrypt code is given? Otherwise, I guess I'll have to simply supply the start and let them work it all out from there.
Very cool ... thanks for the pointer!