Sudoku Daily is a puzzle that uses numbers instead of words. It's a grid of 81 squares, divided into nine blocks of nine squares each. Some of the squares contain a digit. The goal is to fill in the empty squares so that the digits 1 through 9 appear just once in every row, column and individual block.
The aficionados of modern-day Sudoku are keen to point out that it is not a mathematical problem. Logic is what's required.