Nurikabe
Shade the sea so every number sits on an island of that size.
How to play Nurikabe
Nurikabe is a logic puzzle from Japan. The name means an invisible wall from an old folk tale. You get a grid with some numbers in it. Each number is part of an island. Your job is to decide which squares are land and which squares are sea.
Goal
Shade squares to make the sea so that all four rules are true:
- Every number sits on its own island of exactly that many squares. A "3" lives on an island of three squares.
- Each island holds exactly one number, and islands never touch each other side by side.
- All sea squares join up into one connected sea.
- The sea never forms a 2×2 pool of four shaded squares.
Every puzzle here is checked by a solver, so it has exactly one answer.
Step by step
- Choose the Sea tool and tap a square to shade it blue. Tap it again to clear it.
- Choose the Dot tool to mark a square you know is land. Dots are only a help for you. On a computer, a right click places a dot too.
- With the keyboard, move with the arrow keys. Press Space to use the current tool, S for sea, D for a dot and Backspace to clear. T swaps the tool.
- Mistakes turn red: a 2×2 pool, an island that is too big, an island with two numbers, or a closed island of the wrong size.
- Press Undo (or Ctrl+Z) to step back.
Levels
Easy is a 7×7 grid that falls to simple steps. Medium is 9×9 and asks you to think one step ahead. Hard is 10×10 with bigger islands and longer chains of reasoning.
End of the game
The puzzle is solved as soon as your sea matches the answer. You do not need to dot every land square. The timer stops and shows your time. Your game is saved in this browser, so you can come back later. Like shading puzzles? Try Hitori next.
Strategy tips
- Start with the 1s. An island of one is already complete, so all its neighbours are sea.
- Split close numbers. A square that touches two different islands must be sea, or the islands would join.
- Find squares no island can reach. If a square is too far from every number, it has to be sea.
- Watch for pools. When three squares of a 2×2 block are sea, the fourth must be land.
- Keep the sea flowing. If a patch of sea has only one way out, that exit square must be sea too.
- Close finished islands. As soon as an island has all its squares, shade every square around it.
Nurikabe FAQ
Does every puzzle have only one answer?
Yes. Each new puzzle is checked by a solver before you see it, so there is exactly one correct sea.
Do I have to mark land squares with dots?
No. Dots are only notes for you. The puzzle is solved as soon as the shaded squares match the answer.
What is the difference between the levels?
Easy is a 7×7 grid with small islands. Medium is 9×9 and needs some look-ahead. Hard is 10×10 with larger islands and deeper logic.
Is Nurikabe the same as Islands in the Stream?
Yes. Nurikabe is also sold as Islands in the Stream or Cell Structure. The rules are the same.
