A classic to work its neurons with 3 levels of difficulty and assistance for beginners. The grid consists of 81 squares divided into nine 3x3 boxes. These squares are called "regions". The grid must be completed with all the numbers 1 through 9, each to be used once (and only one) in each row, column and region.
Choose the level of difficulty using the knobs Easy, Medium or Hard. The stopwatch starts. Click on a box, then click a number to place it either on the blank button to delete the digit. The Help button allows to propose possible to place the numbers in the selected box. Solution button displays the solution.