🏝️ Nurikabe
🧩 Logic · 0 playsNurikabe
Shade the sea around numbered islands, keeping the water connected and the islands exact.
About Nurikabe
Each number seeds an island of exactly that many white cells, and everything else is shaded as sea. The constraints hold the puzzle taut: islands may not touch one another except diagonally, each island holds exactly one number, the sea must form one connected body, and nowhere may the shading fill a two-by-two square. Every deduction comes from watching these rules press against each other — a cell that no island can reach must be sea, and a sea cell that would strand the water elsewhere cannot be shaded. It is among the most elegant of the Japanese grid puzzles, and among the deepest.
How to Play
Tap a cell to shade it as sea, and again to mark it as island; each number needs an island of exactly that size. Islands may not touch side-by-side, the sea must stay connected, and no two-by-two block may be fully shaded. Work outward from the numbers, marking what each rule forces.
💡 Tips & Strategy
Open with the marks that cost nothing. A cell between two numbered clues, or diagonal between them where their islands would otherwise touch, must be sea. Every 1 is an island already complete, so all four of its neighbours are sea. And any cell that no clue could possibly reach — too far from every number by walking distance — is sea before you think about anything else.
Grow islands by necessity, not preference. When an island short of its size has only one direction to expand, expand it there; when a clue's full territory has exactly one shape that fits, draw it. The moment an island reaches its number, ring it with sea — completion is information, and the ring frequently forces the two-by-two rule somewhere nearby.
Serve the sea's two masters constantly. It must stay connected, so any shading that would strand a pocket of water is wrong, and a sea cell's last open link to the main body must be kept sea. It must avoid two-by-two blocks, so three shaded cells in a square force the fourth to be island — which means some clue must reach it, and tracing which one often settles a whole corridor.
When progress stalls, hunt for the unreachable and the doubly-claimed. A white cell only one clue can reach belongs to that island, which may force the island's route to it. A white cell two islands could reach must not let them meet — if joining is unavoidable except through one cell, that cell is sea. The interplay of reach and separation is the whole of hard nurikabe.