I came here to say the same thing, and you'd already said it. I too love problems like this. A properly designed system like this one will account for every po

I came here to say the same thing, and you'd already said it. I too love problems like this. A properly designed system like this one will account for every possible oddball situation you can come up with -- and if it can't support an especially weird solution out-of-the-box, it will be easily extensible such that it can. Too many people code to the goal and don't try to model the underlying logical concepts.