A rating seems harsh here as the goal is NOT to be an FM. But since it's listed as an FM (even with the demo designation) I feel I have to say not to bother with this unless you are an FM author and you need to see how to add a lantern to a patrolling guard. In this case, demo doesn't mean a part of a larger work, it simply means to demonstrate a single technique.

For entertainment purposes, you can fully enjoy all this "FM" has to offer in about 20 seconds. For FM authors, this was a nice treat to help figure out an approach that was not present in the original game. A moving light-source carried by a guard really changes the way you approach a game where the shadows are so important.

In terms of usefulness to the community, this is a 10! but in terms of playing a FM to get some Thiefiness in... this is a 0.