Su Doku (current version V3.55, April 2009)
The puzzle is displayed in an Excel spreadsheet. The puzzle can be cleared and a new one input manually and saved mid way for completion later.
There are optional different levels of highlighting possible, with a user choice of colour scheme.
1) Original or sure entered numbers can be highlighted to simplify back tracking in case of an error.
2) Any single number at a time can be highlighted to simplify solving the puzzle.
3) Optional prompting can highlight possible squares where a number can [or must] be safely input.
Optional prompting updates a separate table with "pencil marks" [possible numbers that can be input in the corresponding square].
Immediately obvious false inputs are signalled with an "Error" indication.
Download xls file (86k)