How to Play Shikaku

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Shikaku is a logic puzzle played on a grid. It’s a unique puzzle that requires thought, planning, and patience. Enjoy!

The goal of Shikaku is to create blocks of cells filled with the same number:

Divide the grid into rectangular blocks
Each block contains only one number
The number indicates how many cells are contained in the blocks

Shikaku Example, Tips, & Tricks

Let’s work through this example Shikaku puzzle (11×11) to learn some useful tips and tricks for playing Shikaku.

Shikaku Example 2 - Start in the corners

From the Corners

I always find it best to start from a corner (or 2, or 3, or if you’re really lucky all 4).

Let’s look at the top-left corner. The corner box is a 6 so we have to add 5 more 6’s to make a rectangle. A 6 box can only be 3×2 (not possible because of the 8 at column 3) or 2×3 (the correct result).

Now let’s look at the bottom corners. The same strategy applies to both of them. The corner itself is blank, and in both cases the nearby 4 is the only number close enough to make a rectangle with.

Finally, we can check the top-right corner. It’s blank. If we test out our options, we’ll see that it could go 3 across or it could go 3 down.

Work Your Way Out

You can basically continue working your way out from new corners.

Under the 6 box we made, there’s a 3 that has only one direction available. Easy to fill that out!

From the bottom, we’ve made two new “corners.”

The blue “corner” has three options: 8, 3, 6.

The pink “corner” has three options: 6, 4, 2.

Keep On Going

The pink corner is too far from the 4 and the 2, meaning it must be a 6.

Since the pink corner uses the 6, we know that the blue corner can’t use it. The blue corner is way too far away from the 3. Leaving the 8 as the only option.

We can also look at the 2 (below the 3 and above the 8). There’s only one direction to go to finish this box.

And lastly, we’ll look at the top-left 8. It cannot go down because the 3 is in the way, so it must go to the right.

Weird Spaces

Sometimes you’ll have some weird or distant spaces.

Let’s take a look at the yellow lines. The corner square could be included in the 6, 3, or 2. That 2 is way too far away! It cannot be included with the 6 because the 3’s would interfere with making a rectangle. So it must be a three.

Next, look to the blue line. This starts in a box that can only go in one direction and the only number it can touch is the four. This is going to be a rectangle that’s 4 blocks long and only 1 block tall.

Lastly, we have the pink corner. To the right is nothing. The three on a diagonal is too far away. This must go with the 8.