The objective of the game is to place numbers from 1 to 9 in each of the empty cells in a 9x9 grid, consisting of 3x3 sub-grids called regions.

The puzzle contains some initial clues, which are numbers inserted in some cells, in order to allow an induction or deduction of the numbers in cells that are empty. Each column, row and region can only have a number from 1 to 9 each.

The attraction of the game is that the rules are simple, however, the line of reasoning required to achieve the solution can be complex. Sudoku is recommended by some educators as an exercise in logical thinking. The level of difficulty can be selected to match the audience.

Resources:
Identifies repeated numbers in the row, column or region.
Highlights equal numbers in the game to aid identification.
Highlights cells related to the current position helping to identify possible duplication.
Automatically removes numbers that have already been defined in drafts.