> I had a guy last night who's rule was "two pieces make the letter T." > We eventually had to give, but that's probably more due to beer than difficulty or references to externals being dismissed. > > Bad rule or good? I was inclined to say it was outside reference (and did at the time); but I can imagine someone guessing "two pieces same-size touching, one of which exactly bisects the edge of the other one" and that would be so functionally equivalent to describing how to draw the letter T that the guy would have had to give the win. I would say bad for a few different reasons. I'm not sure that the forms you stated are really equivalent. For one thing, you don't have any requirement in the second form that the pieces are perpendicular. But even if you added that, I think there would be some flexibility in what constitutes a T; even things that are visibly not exactly perpendicular or not exactly bisecting might be considered a T. So there is subjectivity at work here. Second, rules that involve an exact position or orientation or any other non-integer quantity are often questionable, unless it is specifically something that is easy to reproduce and easy to distinguish. The only things that come to mind are upright and flat orientations and stacks/nests/trees. I would not consider "The points of all pieces must be in a vertical line" to be a good rule because of what could happen with a small upright inside a large upright. --Bill Barksdale