Sudoku is an addictive number placement game. The user inputs numbers in the blank squares so that each column, row, and each of the 3x3 sub-grids have the numbers 1 through 9. There is usually just one solution, and sometimes it can be a brain-buster – but with enough thought and a cold energy drink on hand, even the hardest puzzle becomes solvable. So, sit back and enjoy a good Sudoku puzzle.