Sudoku is a good online game that trains the brain. The player is waiting for the simple rules of the free game: each of the nine blocks must contain numbers from 1 to 9. The complexity of the online puzzle is that each number can appear once in a row, or column without repetition or gaps. The goal of the player is to fill in the gaps with numbers from 1 to 9 to complete the puzzle. A free online game is automatically generated. There are 7 different backgrounds available for players to change in this free puzzle game.