Fillomino & Sudoku : No one in the puzzle field has hatched as many new brainteasers as Nikoli, publishers of Japan's very first puzzle monthly. Now their blockbuster creation sudoku joins forces with a hot newcomer â fillomino. Like sudoku, fillomino has a simple set of rules that allow for endlessly fascinating possibilities. The challenge: fill a grid with clusters of numbers (2s in groups of 2, 3s in groups of 3, etc.) so that no group touches a group of the same size. America's millions of Sudoku fans will catch on instantly â and they'll be hooked.