Sudoku

Sudoku is a puzzle game where you have to fill a grid made up of 3 x 3 squares with numbers. Each square has a further nine squares and the numbers 1-9 must be used to fill the whole grid. There are twenty grids to play and each grid has numbers already in them to start with. When placing a number, you must take into consideration that a row or column on the whole grid musn't contain the same number and one of the 3 x 3 squares must also not contain the same number. Any of the grids can be edited to create your own puzzles.