unique solution solving tool
I've seen some pieces on how to solve, but never anything on the usefulness of knowing that there's only one valid solution. It can resolve alternatives and at the least speed up solving.
That leads to another question: is it theoretically possible to construct a puzzle where this element is actually necessary? I've tried in a small way, without success, but that doesn't mean it can't be done.
If anyone's feeling philosophical, can that last question be answered?