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 ("boxes") that compose the grid contain all of the digits from 1 to 9. The puzzle starts with a partially completed grid. All puzzles have one and only one solution.

The app includes plenty of 4x4 and 6x6 puzzles for beginners, and hundreds of 8x8 and 9x9 puzzles with varying degrees of difficulty for advanced users and expert solvers, along with the ability to validate progress.