Sashikaku (from Japanese, literally "square by difference") is a logic puzzle created by Nishiyama Yukari (Japan). A rectangular or square grid contains numbers in some cells. The aim is to divide the grid into rectangular and square regions such that each region contains exactly one number, and that number represents the difference of the width and height of the region.
Cross+A can solve puzzles from 3 x 3 to 30 x 30.