Creating Sudoku

Figure 1.
The red-circled cell can take 1 only because 2-9 is already used by other cells of same horizontal group.

Figure 2.
The red-circled cell can take 1-9 but it must take 1 because other cells of same box group cannot take 1 and only the cell can take 1.

Figure 3.
The green-circled 1 is already fixed (see Figure 1). Now you can use it with other three Given 1s to fix red-circled cell's value to 1.

Figure 4-1.
The values of red-boxed three cells are not fixed because they can take 1-3 each other. The 'G' marked two cells are Blank Given and you have the right to decide the value of these two cells to the one of 1-3. But, not only that, you can decide NOT to use the one of 1-3 to the two Blank Givens and select the value from others later.

Figure 4-2.
If you decide not to use 1 to the values of two Blank Givens, You can fix the value of the red-circled cell to 1 because 4-9 are already used by others and 2 and 3 will be used by the two Blank Givens by your decision and only 1 is left for the cell.

Figure 4-3.
The same logic can be applied to 2 and 3 thus you can fix the value of the red-circled cell to any of 1-3 keeping the consistency. If you use calculation of Note menu, Green Note will indicate this (see Using Note section for details).

In creating Sudoku, you can decide the value and the attribute (Given or Answer) of all cells by yourself. But if you do it all at random, soon the consistency of the problem will be lost and you will fail to create. You must think the consistency of problem.

To keep the consistency of the problem, fix the value of each cells eliminating duplicate value of same groups (Figure 1.) and considering whether another cells of same groups can take the value (Figure 2). Note is very helpful for the work (Red Notes show these, see Using Note section for details).

In Figure 1 and 2, all non-circled cells are colored blue because their attribute is Given. If their attribute is Answer, there are no reason why the values of these cells are fixed. In creating Sudoku, this is very important. You can set any value to Given cell for creator's right unless it is not the same value of other cells of same groups (vertical, horizontal and box) but you cannot set any value to Answer cell without assuring the cell can take the value only. This is same as solving Sudoku in finding the only one consistent value.

To assure the consistency of Answer cell you can

• arrange Given cells (Figure 1 and 2).
• use already fixed Answer cells to fix other unfixed Answer cells (Figure 3).
• use Blank Given (see below & Figure 4).

What is Blank Given?
Blank Given is Given cell assigned no value yet and it is shown 'G'. It is used at Edit mode only and must be assigned the value before the finish of creating. But currently you can use it as Given assigned some value like a wildcard. It is useful to make more complicated problem or arrange all Givens first to create geometrically or symmetrically designed Sudoku.
To make the cell to Blank Given, turn Attribute Selector to Given for the selected cell and tap 'C' button to clear the value if any.

There are several patterns of creating sudoku. We have some examples in Tutorial 1 and Tutorial 2 pages.

Summary of tutorials