Arrange all 8 chess pieces of one set (no pawns) on a 5x6 board so no piece attacks another. Never mind that they're all the same color--it's "friendly fire". Be sure that the two bishops are on opposite-colored squares. There are 6 ways, not counting reflections and rotations.
Great puzzle! We have found three different solutions (over an equal number of weeks...). Now we're not sure if we have finished or not.
Say we have a solution on a board where the bottom right square is black. If we put exactly the same solution on a board with a white bottom right square, is that a new solution or simply a rotation? (This is the same as picking up the pieces in the first puzzle with a ten-pin-bowling-like set of pincers, and then spinning the board 180 degrees and dropping the pieces back down. Does this count as a rotation?)
What's a rotation?
