SigmaDokuTM uses the same basic concept as a sudoku puzzle, but now there are two more kinds of clues to help you reach the final solution.  At the intersections of each 4-number square, you may find a sum given, which will help you figure out the four numbers surrounding that sum.  Also, there are shaded pairs or trios of square that indicate matching numbers.  With our new twist to the old classic sudoku puzzles, fewer number clues are needed to get you started, yet keep you challenged.