How to play Shikaku

Shikaku is a logic puzzle in which you divide the whole grid into rectangles. Each rectangle contains exactly one number, and that number tells you how many squares the rectangle covers. A single square counts as a rectangle too. Every square must belong to a rectangle, and each puzzle has exactly one solution that you can find without guessing.

A new two-star Shikaku in Vellara: a 6×6 grid with numbers scattered across empty squares

The Shikaku help screen in Vellara explaining how to divide the grid into rectangles with one number each

Shikaku rules

Divide the entire grid into rectangles (squares count as rectangles too).
Each rectangle contains exactly one number.
That number equals the number of squares in the rectangle.
Rectangles may not overlap, and every square in the grid must be used.
Each puzzle has exactly one solution.

How to solve a Shikaku

Work out which shapes fit

Every number can only become a few shapes. A 5 can only be a strip of 1×5 or 5×1, because 5 cannot be split into anything else. A 4 can be 1×4, 4×1 or 2×2; a 6 can be 1×6, 2×3, 3×2 or 6×1. Start with numbers that have few possible shapes, especially primes like 5 and 7, and those near an edge or corner.

Never two numbers in one rectangle

Each rectangle may contain only one number. So for every possible shape, check whether it would cover another number. If it does, rule it out. Often a number that looked like it had four options has only one left once you do this.

What is left often fills itself

Each rectangle you place takes squares out of play. After a few placements, the remaining empty areas often have only one way to be split up. Look at the squares nobody has claimed yet and ask which number could possibly reach them.

Playing Shikaku in Vellara

Shikaku is one of the puzzles in Vellara that are switched off by default. You will find it at the bottom of the main menu under More puzzles, and you can put it in the main menu yourself in Settings, under Puzzles in the menu.

To draw a rectangle, drag your finger from one corner to the opposite corner, or tap one corner square and then the opposite one. Tap a rectangle to remove it again. A rectangle that cannot be right gets a red border. Check shows how you are doing and Clear starts again. You can make the grid smaller or larger, or fit it to your screen.

There are five levels. The easiest is a 5×5 grid with small rectangles; the hardest is a 12×12 grid, the largest, where you sometimes need to think ahead. Every puzzle has exactly one solution and can be reasoned out completely.

A clock runs while you play, but there is no time pressure. Take as long as you like.

The Shikaku level choice in Vellara: five levels from a 5×5 grid with small rectangles to a 12×12 grid

Shikaku FAQ

Can a rectangle be a square?

Yes. A square is a rectangle too, so a 4 can be a 2×2 block and a 1 is just a single square.

Where can I find Shikaku in Vellara?

Shikaku is off by default. Look at the bottom of the main menu under More puzzles, or switch it on in Settings under Puzzles in the menu.

Does Shikaku always have one solution?

Yes. Every Shikaku in Vellara has exactly one solution, and you never need to guess to find it.

What does a red border mean?

It means the rectangle you drew cannot be right. Tap it to remove it and try a different shape.

Is Shikaku free to play?

Yes. Vellara is free to download and play, and you don't need an account.

Download Vellara

Vellara is free for iOS and Android, needs no account, works offline and never sends you notifications.

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