Among free sudoku games online there are number puzzles which provide additional challenge. This brain-teaser combines rules of the classic sudoku game and a Math puzzles. Not only you have to fill in the grid with numbers unique in their row and line, but also meet the condition of each segment separated by thick borders. For example, 3÷ means that the sum of all the numbers in the segment can be divided into 3. 2- means that their difference equals two. The settings allow users to adjust the difficulty level and the grid size, so that all fans of pen and paper games may choose a puzzle to match their skills. Moreover you may also solve daily sudoku puzzles free online. They are fun learning game for preschool children to develop logic skills and practice basic Math.