Shikaku

Shikaku (四角に切れ) (also anglicised as Divide by Box or Rectangles ) is a logic puzzle published by Nikoli.

History
The game was invented by Yoshiano Anpuku, a math student at the University of Kyoto, in 1989 and published by Japanese games magazine Nikoli under the name "Shikaku". The puzzle later spread to other publications and has been adapted into video games.

Rules
Shikaku is played on a rectangular grid. Some of the squares in the grid are numbered. The objective is to divide the grid into rectangular and square pieces such that each piece contains exactly one number, and that number represents the area of the rectangle.

Computational complexity
Determining whether a given instance of Shikaku has a valid solution has been proven to be NP-complete.