To play this game you have to fill in the grid so that every row,
column, and 3x3 box contains the digits 1 through 9.

The following grid show you all the 3x3 box
(different shade of blue)

BASIC TECHNICS

The basic solving technics are : missing digit, space left, virtual digit, pairs, triples and quads.

1. Missing digit : Look at the digits already in the same line, column and 3x3 box of a cell and to
see if only one digit from 1 to 9 is missing. Example, if for a cell, you have digits 2,3,4 in the
same line; 4,5,6 in the same column; and 6,7,8,9 in the 3x3 box, you know that the missing digit
1 have to be there.

2. Space left : Take a look at a 3x3 box and search for the presence of a missing digit in the other
3x3 box. Based on the fact that a digit can't be twice in the same row and column, you can
eliminate places (cells) inside the 3x3 box for this missing digit. You may find by this technic
only one space (cell) left inside a 3x3 box for a missing digit.

3. Virtual digit : This technic is based on the virtual presence of a digit in some cells to allow
eliminate this possible digit in other cells. If digit 2 is possible only in two cells of a 3x3 box
and these two cells are also in the same line, then the digit 2 can't be in the other cells of this
line.

4. Pairs, Triples and Quads : This technic need to take a note of the possibilities for each cell.
When looking at the possibilities for cells of a line, a column or a 3x3 box, you may find a pair,
triple or quad of possibilities that allow you to reduce the possibilities. Examples : If only two
cells in a line have the possibilities 5 and 8, and if at least one of these cells have more
possibilities, then erase these extra possibilities because you find an hidden pair. If two cells in
a column have the same two (and only two) possibilities (no extra), these possibilities can't be
elsewhere in this column and this is called a naked pair. If three cells have a total of only 3
possibilities, whatever is the distribution of these 3 possibilities in these cells (can be something
like 1-2-3, 2-3 and 1-3; or 1-2, 2-3 and 1-3), you find out a naked triple and these possibilies
can't be in the other cells.

ADVANCED TECHNICS

X-Wing technic is based on the virtual presence of a digit in 4 cells that allow to eliminate its
possibility in other cells. In the example, you have two columns (in blue) with only two possible cells (in green) for the digit 3. These cells are also in the same two lines (in orange). This particular situation allow to eliminate the possibility of digit 3 in the two cells in red. The logic said that if 3 is finally present in one of these green cells, another 3 will be automatically at the opposite green cells and this particular situation reserve these four cells for the digit 3 in these lines.

XY-Wing technic is based on a small chain-reaction that doesn't allow a possible digit for a cell. First, find a cell with only 2 possibilities (7 and 9 in the example). Then check if choosing these possiblities give the same digit answer for two others cells (7 gives 3 in the same line, and 9 gives 3 in the same column). And if these two other cells are aligned with another cell that contains this digit in its possibilities (in red in the example), then you find a XY-Wing case. In example, because choosing 7 or 9 give the answer 3 in two cells aligned with the red cell, then 3 can't be the answer for this red cell.

FANTASY PUZZLES

The fantasy is the pattern for the given digits and the colors. The colors make puzzles looking cool, had no effect for the game. These pattern are generally symmetrical and may represent something like a logo, a profile, popular figure or something similar. The centered 3x3 box is colored yellow in most of the patterns to make it more easier to detect the presence of the 3x3 box in the grids.

A BIG Thanks to our friend Daniel Bienvenu for designing and donating these Videogame based Su-Doku Puzzles for all of our enjoyment :-)