Nurikabe

Overview

Nurikabe divides a grid into numbered islands and a continuous sea. Each island consists of orthogonally connected white squares and contains exactly one clue equal to the island's size. Different islands cannot share an edge. The black sea must remain connected and may not contain a solid two-by-two block. Islands may touch at a corner without merging. These rules make the shape of empty space as important as the numbered regions themselves. The locally hosted pzpr player supplies one introductory five-by-five puzzle with a checked reference solution. Its practice selector rotates or reflects that board; these are clearly labelled transformations of one puzzle, not a collection of independent levels. Check answer provides feedback without requiring an account or a remote service.

How to Play

Click or drag through unnumbered squares to shade them as sea. Secondary input marks squares that belong to white islands; on a phone, use the Secondary toggle for that action. Leave numbered cells as part of their islands. Build each island to exactly its clue size, then ensure the surrounding sea joins into one connected region and contains no two-by-two black block. Press Check answer to inspect the result. Undo revises a mark, while Restart clears the current orientation without changing its clues.

Tips & Strategy

A clue of one is a complete island, so all its edge neighbours must be sea. Two different clues separated by a single square often force that intervening square black to prevent their islands merging. Look for a two-by-two area with three confirmed sea cells: the fourth must remain white. At the same time, protect a route connecting separate patches of sea. A tempting island extension may seal a black cell into an isolated pocket. Count an island's available room as well as its current size; a large clue trapped in a small space exposes a mistaken sea boundary.

About this version

Nurikabe uses the locally built nurikabe rules from pzprjs. The original authors retain credit under the MIT license. SonoTap provides the browser adaptation and this guide.