Here's a hard one I created:  a descriptive sudoku.  The solution is unique. In a Jigsaw sudoku, numbers 1-9 occur once in each row, column and irregular 9-square region.  One jigsaw sudoku has three non-touching 3x3 squares, each filled with the digits 1-9 in order, and each touching 2 or 3 of the other six *identically-shaped* regions. One 3x3 square is in the upper left corner, and another is high up on the right side.  The main diagonal has four 1's.  As a hint, the identical shape used in the six regions is a 2x4 rectangle with a square added to one corner. Ed Pegg Jr