Nurikabe
Nurikabe is a logic puzzle about islands in a sea. Each number is part of an island with exactly that many cells. Shade every other cell as sea so that the sea is one connected area, islands never touch side by side, and no 2×2 block is all sea.
How to play
Every Nurikabe here has exactly one solution and can be solved by logic alone. The grid grows from 6×6 at Easy to 8×8, and the level is set by the hardest technique the puzzle needs.
- Each island holds exactly one number, and its cell count equals that number.
- Islands never touch each other side by side.
- All sea cells form one connected area.
- No 2×2 block is entirely sea.
Playing on this site
- Tap a cell to shade it as sea, tap again for a dot that marks it as island, and once more to clear it.
- Drag across cells to paint the same mark along the way; the whole drag is one undo step.
- With a keyboard, use the arrow keys to move and Space to cycle the mark.
- Dots are only a helper: the puzzle is solved as soon as the sea is right.
- Hint points out wrong cells first, then names the next technique and highlights where it applies.
- Your puzzle is saved in this browser, so you can come back to it later.
Techniques by level
Every technique the solver knows, from easiest to hardest. A puzzle's level is the hardest one it needs.
Easy
- Island complete
- This island has as many cells as its number, so every cell around it is sea.
- Between two islands
- This cell touches two numbered islands; as land it would join them, so it is sea.
- No 2×2 sea
- Three cells of this square are sea; the sea never fills a 2×2 block, so the fourth is land.
- Out of reach
- No island can grow far enough to reach these cells, so they are sea.
Medium
- Only way out
- This island still needs cells, and it can only grow through one cell.
- Sea must connect
- This part of the sea has one way to reach the rest, so that cell is sea too.
Hard
- Look one step ahead
- The other choice here breaks a rule straight away: a pool, an island too big or too small, or a cut sea.
Expert
- Contradiction
- Assume the opposite in the marked cell and a rule breaks a few steps later. So it can only be this.
Questions
Where do I start a Nurikabe?
Shade the cells between two numbers that touch both, and wall in every 1 at once. Then look for islands that have only one way left to grow.
Will I ever have to guess?
No. Every puzzle has exactly one solution that logic alone reaches, at every level.
Is Nurikabe free to play here?
Yes. Every level is free, with no account and no sign-in.