Sudoku is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9×9 grid with digits so that
each column, each row, and each of the nine 3×3 subgrids that compose the grid (also called "boxes", "blocks", or "regions")
contains all of the digits from 1 to 9. The puzzle setter provides a partially completed grid, which for a well-posed puzzle
has a single solution.
Sudoku is mainly a CSP(Constraint satisfaction problem), central point in this game is how to generate a random board with a unique solution. Detailed design and instructions can be found in the reference below.
Here are the screenshots of games:
https://en.wikipedia.org/wiki/Sudoku
https://en.wikipedia.org/wiki/Constraint_satisfaction_problem
https://stackoverflow.com/questions/6924216/how-to-generate-sudoku-boards-with-unique-solutions