I was puzzled about Sudoku, mentioned in a recent message. It's apparently well known on the puzzle circuit. Here's an example I swiped from last Monday's USA Today -- they've started running a daily puzzle. - 6 - | 3 - 8 | - 7 - - - - | - - - | - - - 4 3 - | 6 - 1 | - 9 5 ------+-------+------ - - 5 | - 4 - | 7 - - - - - | - 1 - | - - - - - 1 | - 2 - | 8 - - ------+-------+------ 9 2 - | 4 - 5 | - 3 6 - - - | - - - | - - - - 8 - | 7 - 9 | - 4 - In a completed sudoku, each row and column of the puzzle has one occurence of each digit from 1-9. (This makes it a Latin Square.) In addition, each of the nine marked 3x3 subsquares has (one of) each digit. The solver's job is to fill in the blanks in the puzzle. I think the one above would qualify as simple; I was able to complete it without much "advanced reasoning". Rich rcs@cs.arizona.edu