Infinite Sudoku description

The game has 4 levels of difficulty, automatically generate Sudoku. Sudoku is one of the most popular puzzle games of all time. Sudoku is a puzzle with a grid containing nine large blocks. Every Sudoku has a unique solution that can be reached logically. Enter numbers into the blank spaces so that each row, column and 3x3 box contains the numbers 1 to 9. The rules for solving Sudoku puzzles are very simple: each row, column and block must contain one of the numbers from 1 to 9. No number may appear more than once in any row, column, or block. When you've filled the entire grid, the puzzle is solved.