In the Sudoku game you have to fill a 9x9 board with numbers, but cannot use the same number twice in the same row, column and block.
Start a new game with your preferred difficulty setting. Select a cell and afterwards select the number you want to fill into it.
Win the game by filling the correct number in all empty cells. There's only one correct value for each cell.
You start the game with a limited number of lifes. You loose a life each time you fill a wrong number into a cell. Once all lifes are gone it's game over.