Matrix Sudoku 2.26

Matrix Sudoku is a popular and Brain Training puzzle consisting of a grid of 9 by 9 numbers. Each grid number is in the range 1-9 which can only occur once in any row/column combination and the 3x3 square in which it resides. Sudoku is a Japanese word that means the numbers must be single, or the numbers must occur only once. The goal of Sudoku is to fill all the blank squares in the grid with the correct numbers. Matrix Sudoku also support the variant sudoku: Nonomino Sudoku, also known as geometric Sudoku. This variation most closely approximates regular Sudoku, but instead of nine 3x3 groups, it has nine groups in irregular nonomino shapes. Version 2.26 adds a new feature - Pencil mark.