The History of Shikaku: Nikoli's \"Cut Into Squares\" Puzzle

Shikaku has the calm, timeless feel of a puzzle that has always existed, a grid quietly waiting to be sliced into tidy rectangles. In fact it is a modern invention with a clear inventor, a precise birth year, and a name that says exactly what you do. It comes from the same Japanese workshop that gave the world Sudoku, and its story is a neat reminder that some of the best puzzles started as a bright idea from an ordinary solver. Here is where Shikaku came from. When you are done, you can play one yourself.

Invented by a student in 1989

Unlike many puzzles whose origins are murky, Shikaku has a known creator. It was invented in 1989 by Yoshinao Anpuku, who was a university student in Kyoto at the time, and it was published by Nikoli, the legendary Japanese puzzle company. It is a lovely origin story: not a committee or a computer, but a student with a clever idea for cutting a grid into numbered rectangles.

Nikoli, of course, is no ordinary publisher. It is the company that took an obscure American puzzle, refined it, renamed it Sudoku, and set off a global craze. The same workshop is behind a whole family of beloved logic puzzles, including Kakuro, Nurikabe and Slitherlink, and Shikaku joined that catalogue as one of its most elegant entries.

What the name means

The Japanese name is wonderfully literal. Shikaku comes from the phrase 四角に切れ (shikaku ni kire), which means roughly "cut it into squares" (四角 means "square," and 切れ means "cut"). That is precisely the puzzle: you cut the grid into rectangular pieces, each sized by its number. Few puzzle names describe their puzzle so directly.

As the puzzle spread, it picked up other names, including Cellblocks (used by The Guardian newspaper), Divide by Box (Nikoli's English name), and the plain Rectangles. We cover that naming story in full in our piece on the puzzle's many names.

The elegance of two rules

Part of what makes Shikaku stand out, even among Nikoli's inventive catalogue, is its simplicity. Where Nurikabe and Hitori juggle four or more rules, Shikaku has essentially two: divide the whole grid into rectangles, and make each rectangle contain one number equal to its area. That is the entire rulebook.

That simplicity is deceptive, though. From two short rules comes a surprising amount of depth, because every number can often be made into a rectangle several different ways, and the puzzle is about working out which combination tiles the grid perfectly. "Easy to learn, hard to master" is the hallmark of a great Nikoli puzzle, and Shikaku is a textbook example.

A puzzle that travelled (and taught)

Shikaku turned out to travel exceptionally well. Built from numbers and shapes rather than language, it needs no translation, and it found enthusiastic audiences far beyond Japan, with an especially strong following in Germany and across Europe. Nikoli published more than a dozen books of Shikaku puzzles, and the puzzle's demand worldwide vastly outstrips any single English-speaking market.

It also earned a reputation as an unusually educational puzzle. Because every clue is really a factoring problem (a number's rectangle is its width times its height), Nikoli positioned Shikaku as a maths trainer that quietly teaches multiplication. We explore that angle in Shikaku for math. Few pastimes manage to be both a relaxing hobby and a genuine learning tool.

Where it stands today

Shikaku now sits comfortably in the canon of classic logic puzzles, alongside its Nikoli siblings. It is available on dedicated puzzle sites, in apps, and in puzzle books worldwide, in grid sizes from quick 5×5 starters to demanding 15×15 challenges, and it appears as a daily newspaper puzzle under names like Cellblocks. Not bad for an idea a Kyoto student had in 1989.

The next chapter of Shikaku's history is the one you write every time you slice a grid into rectangles. Play Shikaku now, or learn the rules if you are new to it.

Frequently asked questions

Who invented Shikaku?

Shikaku was invented in 1989 by Yoshinao Anpuku, then a university student in Kyoto, and published by Nikoli, the Japanese puzzle company famous for popularising Sudoku. It has a known individual creator, which is unusual among classic logic puzzles.

When was Shikaku created?

Shikaku was created in 1989 and published by Nikoli. That places it in the same modern era and from the same publisher that later brought Sudoku to worldwide attention.

What does "shikaku ni kire" mean?

四角に切れ (shikaku ni kire) is the puzzle's full Japanese name, meaning roughly "cut it into squares." It describes the goal directly: you cut, or divide, the grid into rectangular pieces, each sized to match its number.

Is Shikaku a Nikoli puzzle?

Yes. Shikaku is a Nikoli puzzle, invented in 1989 and published by the company. Nikoli is the same Japanese publisher that popularised Sudoku, Kakuro, Nurikabe and Slitherlink, and it is known for handcrafted puzzles with a single logical solution.