Sudoku is a logic-based puzzle, in which you have to place number to correct positions. The objective is to fill a 9x9 grid so that each column, each row, and each of the nine 3x3 boxes contains the digits from 1 to 9, only one time each (that is, exclusively). Good luck in solving Sudoku :)
A context menu should be shown when right-clicking or, on touch devices, long-pressing in the game. This menu especially allows to play in full screen and control the volume.