To solve the puzzle, every square in the grid has to contain a single number between 1 and 9 while adhering to the following three rules:

One	Two	Three
Every vertical column of 9 squares must contain each of the numbers from 1 to 9 once and only once	Every horizontal row of 9 squares must contain each of the numbers from 1 to 9 once and only once	Each of the 9 - 3 x 3 boxes must contain each of the numbers from 1 to 9 once and only once

A new game starts with a partially completed grid and the object of the game is to fill in the remaining squares using the rules above to guide you. The game is finished when all squares have the correct number in them.

To fill a square with a number, tap on the square to select it; you will see it is highlighted. Then tap on your number of choice from the row of number selection buttons located below the game board.