Any particular reason for this change? Just wondering.
Yes: my daughter (who is 6) has started doing the puzzles, and she found the
transition from 4x4 easy (addition only) to 4x4 medium (all four operators suddenly)
a bit hard
Get the 2nd edition of my Huge Killer Sudoku book at http://www.amazon.com/Huge-Killer-Sudok ... 148952987X
(replace .com with .co.uk, .de, .it, .fr, or .es to order from those countries)