iNumberBoard app for iPhone and iPad

NumberBoard (called Sudoku) is a numbers puzzle that is very popular in the world.
In order to complete the puzzle, you must fill each cell with a number between 1 and 9, inclusive, such that no number is repeated in any row, column or 3x3 box.
In a solved sudoku, each row, column, and 3x3 box contains all the numbers 1 through 9.
In this version, there are 2 levels: Easy and Hard. With each level, players can try with different number patterns.
In order to win, players must have a clear strategy. If you enter the wrong number in a cell, the player can clear them away and fill others