Shikaku

Cut the grid into rectangles. Each one holds a single number, and that number is exactly how many squares the rectangle covers.

Loads instantly in your browser — no download.

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Size

Responsive 640 × 480 800 × 600

Responsive keeps the frame inside your column on a phone. Fixed sizes are easier to drop into an older layout.

HTML to paste

<div style="position:relative;width:100%;aspect-ratio:16/10">
  <iframe src="https://www.gamedavinci.com/embed/shikaku/" title="Shikaku"
    style="position:absolute;inset:0;width:100%;height:100%;border:0"
    allow="fullscreen; autoplay; gamepad" loading="lazy"></iframe>
</div>
<p><a href="https://www.gamedavinci.com/game/shikaku/">Shikaku</a> by <a href="https://www.gamedavinci.com/">GameDavinci</a></p>

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Daily challenge

Shikaku serves one puzzle a day, generated from the calendar date — so the board you play is the same board every other player gets. Solve it before the day is out to extend your streak. Your stats stay in this browser; there is nothing to sign up for.

Next puzzle in under 24 hours . See all daily challenges →

About this game

Shikaku is a puzzle with one rule and no arithmetic worth the name. Divide the whole grid into rectangles so that every rectangle contains exactly one number, and every number is the area of the rectangle it sits in. A 6 is a rectangle of six squares — one by six, two by three, six by one — and which of those it is depends entirely on what the rectangles around it need. The pleasure is that nothing is ever nearly right. A rectangle either has one number in it or it does not; it either covers as many squares as that number says or it does not. Both are visible the instant you draw it, so a mistake is caught where it was made rather than twenty moves later. Every square must end up covered, and that is the constraint doing most of the work: a corner square reachable by only one rectangle settles that rectangle before you have looked at anything else. Boards are cut in the browser and proved before you see them. The proof is not that an answer exists but that a player can reach it — a solver that only ever places forced rectangles, never guesses, has to finish the grid before the board is dealt. Gentle boards fall to counting placements alone; Hard boards are only called Hard once the harder deduction has been shown to be necessary. Three sizes, a level ladder, and one shared board a day.

Controls

Drag from one square to another to draw the rectangle between them. The running area is shown while you drag, so you never have to count squares by eye.

Tap a rectangle you have already drawn to take it back
Drawing across an existing rectangle replaces it, so a correction is one gesture rather than three
Undo steps back through your rectangles, as does Z
The Size button cycles 7x7, 9x9 and 12x12

How to play

Cut the whole grid into rectangles, one number per rectangle, each number equal to the area of its own rectangle.

The rule

Every rectangle must contain exactly one number
Every number must equal the number of squares in its rectangle
Every square must end up inside some rectangle, with no overlaps and nothing left over

Drawing

Drag from one corner to another and the rectangle between them is what you get. The area counts up as you drag
A rectangle that breaks the rule turns red immediately, so nothing wrong ever stays on the board unnoticed
Tap a rectangle to remove it, or drag straight over it to replace it

Where to start

Corners and edges. A square in the corner can only be reached by rectangles that run along the two edges meeting there, and there are usually very few
Numbers whose area is prime. A 5 is one by five or five by one, never anything else, so it only has two orientations to try
Numbers sitting next to each other. Two 2s side by side cannot both run in the same direction through the same squares

Read the full Shikaku rules and strategy →