A popular number-placement puzzle. A 9×9 grid is divided into nine 3×3 sub-grids (81 squares in total).  The grid already contains some digits. The objective is to fill free squares with digits (from 1 to 9) so that each column, each row, and each of the nine 3×3 sub-grids that compose the grid contains all the nine digits.  Use the navigation buttons on the remote to move along the grid. To place a digit, press a corresponding button on the remote (digital section). The button deletes a digit from a square.