Play Nurikabe Online — Free
Shade cells to create a connected sea of black cells. Each numbered white island must have exactly that many white cells and islands cannot touch each other.
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About Nurikabe
Nurikabe is a classic Nikoli puzzle often described as an island-building exercise. The grid is divided into “islands” (white connected regions) and a “sea” (the black cells). Each island is anchored by a numbered cell, and that number tells you the exact size of the island. All remaining cells are sea, and the sea must form one fully connected group.
Three rules make Nurikabe demanding: islands of different numbers cannot touch each other, no 2×2 block of sea cells is allowed, and every island must be exactly the right size. These constraints interact subtly — an island that cannot grow forces nearby cells to be sea, which then cannot form 2×2 blocks, which constrains island shapes elsewhere.
Nurikabe rewards patient, methodical solvers who track island connectivity and sea connectivity simultaneously. It’s one of the most celebrated Nikoli puzzles alongside Slitherlink and Hashi, and its difficulty range is enormous — from beginner-friendly small grids to marathon-level expert challenges.
White cells that cannot be reached by any numbered island — too far away or surrounded by other islands — must be sea. Identifying these “unreachable” cells early is one of the most powerful Nurikabe techniques.
Frequently asked questions
What is Nurikabe?
Nurikabe is a logic puzzle where you shade cells to form a single connected sea. White islands each contain exactly one number equal to their size, and islands cannot touch each other horizontally or vertically.