"Shikaku" is one of Nikoli's own original casse-tête, with simple rules and a unique feeling of solution. Until you get used to it, you'll tend to solve the casse-tête with guesswork, but the real charm lies in solving them with logic. Once you master the method of solving the casse-tête by gradually stretching squares from the numbers, you'll be able to enjoy "Shikaku" on an even deeper level.