Nurikabe

About Nurikabe

Nurikabe is a Japanese logic puzzle about islands and a sea wall. The grid starts blank except for a few numbers. Each number is an island of exactly that many unshaded squares, and your job is to shade every other square so that all the shaded squares join into one wall, with no 2 × 2 block of wall anywhere. Islands never touch each other across a side, so the wall weaves between them like a river. Dots help you remember which squares you know are island. Easy days are 7 × 7, medium 8 × 8 and hard 10 × 10, and every grid has one answer that you can reach by logic alone.

How to play Nurikabe

1. Every number sits in an island: a group of unshaded squares joined across or down, with exactly as many squares as the number. Each island holds one number, and no unshaded square is left outside an island.
2. All the shaded squares form one wall, joined across or down, and the wall never fills a 2 × 2 block.
3. Tap a square to shade it, again for a dot (a note for a square you know is island), and once more to clear it. Drag across squares to paint; a long press or a right click places a dot. Dot first in the options swaps the order.
4. Easy grids are 7 × 7, medium 8 × 8 and hard 10 × 10. Every grid has one answer, found by logic alone. Fastest time wins; fewer changes break ties.

Tips & strategy

• Start with the 1s: every square beside a 1 is wall. Then shade any square that touches two different numbers, since two islands may never meet.
• A square that no island can reach (too far from every number for its size) has to be wall. Count the steps from each number.
• Look for 2 × 2 blocks with three wall squares already: the fourth square must be island, and usually only one number can reach it.
• The wall must stay in one piece. A piece of wall with only one way out has to grow through that square.

Nurikabe: questions and answers