Finding difficult puzzles: "The best such puzzles are easy to explain, yet difficult to solve. Historically, they have been devised by trial and error. But earlier this year, Jim Lewis, an inventor based in Midland Park, New Jersey, set out to find the hardest possible “simple” puzzle, using a computer-based search.".
We got onto this subject yesterday at the sushiFest, talking about Suicide Chess and Bastard Tetris: both games which take an established, understood game environment and turn it on its head by a simple change of the rules/behaviour.