The sudoku is an ancient Japanese puzzle

It consists of a 9 x 9 grid grouped in 3 x 3 boxes, and the objective is to fill every cell with a number between 1 and 9

Every cell's digit must be unique to its row, column and box.

To draw a number in a cell select it by clicking/tapping on the cell and then click/tap on the desired number.

The digit mode allows the user to write only one number on the cell, whereas the candidate mode is used to write multiple possibilities (candidates) for that cell.

Whenever there is an error on a cell all the conflicting cell's change color.

• D: change to digit (normal) mode
• C: change to candidate (small) mode
• 1-9: draw the number on the selected cell
• Del: remove digits from selected cell (within the current mode)