Solving Sudoku Has Nothing to Do with Arithmetic

My mother and my older sister both play Sudoku, and I play now and then myself.

Once, while teaching my daughter to play, it suddenly struck me: solving Sudoku has nothing to do with addition, subtraction, multiplication or division. It is purely a matter of arrangement: nine different things, each appearing once in every row, every column and every box.

If it is only arrangement, it does not need to be numbers at all. We are just used to them.

In that case, the evolutions from Baby Guardian Battle could be used too.

Pictures Are Not as Familiar as Numbers

While making it, I found that pictures alone are simply not as familiar to us as numbers.

So I added a Mixed mode, where numbers and pictures appear together, an indirect and gradual way to get used to them.

To Build the Hints, I Studied Sudoku More Deeply

As I went on, I also found that Sudoku can be very simple or very deep, with all kinds of solving techniques:

Last cell　a box, row or column with one empty cell left: the answer is the missing number
Hidden Single　a number with only one place left in a box (or row, or column)
Naked Single　a cell whose row, column and box already show eight different numbers: the missing one is its answer
Pointing Pair　a number inside one box can only sit on the same row (or column), so the rest of that line is ruled out
Box–Line Reduction　a number on one row (or column) can only sit inside the same box, so the rest of that box is ruled out
Naked Pair　two cells left with the same two candidates, so no other cell in that area can use those two
X-Wing　a number confined to the same two columns on two rows, so the rest of those columns are ruled out

Most people only know the Hidden Single, and that is enough to get through easy puzzles. I used to be the same.

But harder puzzles need more advanced techniques.

So I thought I would add hints that teach, instead of ones that just hand you a number.

To build that feature, I had to study Sudoku much more deeply myself.

What I found is that using advanced techniques in picture mode really is hard. Number mode is simply more practical.

But on Easy, picture mode is a lot of fun. Once you are tired of numbers, it is a different kind of enjoyment.

When I gave it to my daughter, she was busy playing Baby Guardian Battle.

Maybe when she is a little older, she will be more interested in Sudoku.