Rectangles and Shikaku: one puzzle, two names
If you found this page hunting for the Rectangles puzzle from a newspaper app or puzzle collection, you're in the right place — Rectangles is the English publisher name for Shikaku, the rectangle-division puzzle Nikoli has printed in Japan since 1989. Some apps call it Divide by Box or Cellblocks; the rules never change.
Those rules in full: divide the whole grid into rectangles and squares so that every rectangle contains exactly one number, and that number equals the rectangle's area. A 4 can be a 1×4 strip, a 4×1 strip, or a 2×2 square. Pieces can't overlap, and no cell may be left over. Each puzzle has exactly one valid carving — finding it is the game.
Why the Rectangles format is worth your coffee break
Rectangles hits a rare balance: the rules take thirty seconds to learn, but the deduction runs genuinely deep. Because every number constrains shape as well as size, information compounds fast — a placed rectangle walls off its neighbors, a prime number can only stretch in a line, and a crowded corner may leave one clue a single legal home. On our harder boards you'll chain those observations several steps ahead.
Every board on this site is machine-verified to a single solution and graded easy, medium, or hard by a solver that mimics human technique — so you never need to guess, and a difficulty label actually means something. Start with the board above, then browse all sizes from 5×5 to 20×20 or make the daily puzzle a habit.