To solve Nurikabe, find the wall first. A complete island is closed in by wall; a square touching two islands is wall; a square no island can reach is wall. Then grow the islands that have only one way to go, keep the wall in one piece, and never let it fill a 2×2 block. Seven techniques cover every puzzle in the game.
New to Nurikabe? Read the Nurikabe rules first. This page assumes you know the four: islands the size of their number, one number each, one joined-up wall, and no 2×2 blocks of wall.
1. Complete islands
An island with all its squares is closed in: every square around it is wall. A 1 is complete from the start.
2. Between islands
A square touching two different islands is wall, because as island it would join them into one island with two numbers.
3. Out of reach
Each island can only grow as far as its number allows, and never next to another island. A square no island can reach is wall. It does more work than any other technique.
4. An island with one way to grow
An island still short of squares, with only one square it could grow into, grows there.
5. A wall with one way out
The wall has to be one piece. A piece of wall with only one way out, while there’s wall elsewhere, goes that way.
6. No pools
A 2×2 block with three walls has its fourth square in an island. Watch for it wherever the wall gets thick.
7. What if
When nothing else works, pick a square and suppose it’s wall, or island. Follow what that forces. If a rule breaks, it’s the other way. The what-if page follows one through a real puzzle.
How often each technique is needed
We solved every one of the game’s 150 levels by following the hints, which always use the simplest technique that works. This is how many times each technique was used, on average, per level:
| Technique | Easy 6×6 | Medium 8×8 | Hard 10×10 |
|---|---|---|---|
| Complete islands | 5.1 | 9.3 | 14.8 |
| Between islands | 1.6 | 3.3 | 4.8 |
| Out of reach | 10.6 | 15.8 | 22.6 |
| An island with one way to grow | 1.7 | 2.5 | 3.4 |
| A wall with one way out | 0.8 | 1.2 | 1.3 |
| No pools | 3.8 | 7.4 | 12.1 |
| What if | 0 | 4.4 | 8.0 |
Out of reach does the most work on every track. No pools is needed on 49 of the 50 Easy levels and every Medium and Hard one; what-if on 44 Medium levels and every Hard one.
An 8×8, solved in stages
This is Medium level 1 from the game.
Stage 1: the easy walls
There are no 1s here, so the first moves are squares between two islands: 7 of them. Then come the squares out of reach of every island: 17 more. That’s the first 24 steps, all wall.
Stage 2: islands with one way to grow
The 2 in row 1, column 4 is now walled in on every side but one: it grows to its left.
Stage 3: a wall with one way out
The wall square in row 8, column 2 sits between the 3 above it and the 2 to its right. To join the rest of the wall, it has to go left.
Stage 4: no pools
Row 2, columns 7 and 8 and row 3, column 8 are wall. The fourth square of that 2×2 block, row 3, column 7, must be island.
In all, the level takes 48 steps: 6 from complete islands, 7 between islands, 17 out of reach, 8 where an island has one way to grow, 6 where the wall has one way out, and 4 from no pools.
When you get stuck
- Wall in every complete island, and every square between two islands.
- Check what each island can still reach. Anything out of reach of all of them is wall.
- Look for islands and pieces of wall with only one way out.
- Check every 2×2 block with three walls.
- Don’t guess. Every puzzle here can be finished by logic.