What Is Nurikabe?
Nurikabe appeared in Nikoli in March 1991 and takes its name from a wall-like figure in Japanese folklore. The puzzle asks you to divide a grid into numbered islands and one connected sea. The numbers tell you each island's size, while the shaded sea must connect without forming any 2x2 pools. It looks calm. It bites later. The main challenge is balancing island growth against sea connectivity. Start by expanding certain islands and marking cells that cannot reach any clue.
How to Play Nurikabe
- Treat numbered cells as island seeds.
- Grow each island to match its number exactly.
- Shade cells that belong to the sea.
- Keep all shaded sea cells connected through side contact.
- Do not create any 2x2 block of shaded cells.
- Finish when every cell is either part of one valid island or the connected sea.
Basic Rules
- Each island contains exactly one number.
- The number gives the exact size of that island.
- Different islands may not touch horizontally or vertically.
- All shaded cells form one connected sea.
- The sea may not contain a 2x2 shaded block.
- Diagonal touching does not connect islands or sea regions.
Strategy Tips for Beginners
- Mark cells between two completed islands as sea because islands cannot touch.
- If an unnumbered cell cannot reach any island clue in time, shade it as sea.
- Watch for 2x2 sea traps. When three cells in a 2x2 square are shaded, the fourth must be island.
- Grow large islands through forced corridors before shading nearby cells.
- Use sea connectivity. A shaded pocket that cannot connect to the main sea signals a wrong assumption.
Real Examples of Gameplay
Completed Island
A 2 clue already has one connected white neighbor. The island is complete, so every side cell around that two-cell island must be sea.
Pool Prevention
Three cells in a 2x2 square are shaded. The last cell cannot be shaded, or the sea would form a forbidden pool.
Unreachable Cell
A blank cell sits too far from every unfinished island and is boxed away by completed islands. It must join the sea.
Variations of Nurikabe
- Hitori: Also uses shading and connectivity, but starts from duplicate numbers.
- Slitherlink: Uses numbered clues to draw a loop instead of islands.
- Tapa: A shaded-cell puzzle where numbers describe groups of shaded neighbors.
Why People Love Nurikabe
- The island and sea theme makes deductions visual.
- The 2x2 sea rule creates crisp local logic.
- Large islands reward forward planning.
- Hard puzzles often hinge on one elegant connectivity deduction.
Play Nurikabe Online for Free
Play Nurikabe online for free. Grow islands, connect the sea, and avoid 2x2 shaded pools. Begin with small grids, then move to larger puzzles once island-size logic feels natural.
Comparison
| Version | Difficulty | Players | Typical Time |
|---|---|---|---|
| Small Nurikabe | Easy | 1 | 8 to 12 min |
| Medium Nurikabe | Medium | 1 | 12 to 20 min |
| Large Nurikabe | Hard | 1 | 20 to 35 min |
Frequently Asked Questions
Can two islands touch diagonally?
Yes. Islands cannot touch by sides, but diagonal contact is allowed.
What is a 2x2 pool?
It is a square of four shaded cells. Nurikabe rules forbid that shape in the sea.
Can an island have two numbers?
No. Each island must contain exactly one numbered clue.
Start Playing Now
Nurikabe turns a grid into a clean island-and-sea deduction puzzle. Count island sizes, keep the sea connected, and stop every 2x2 pool before it forms.