Nurikabe: The Japanese Puzzle You've Never Heard Of

I found Nurikabe while researching Japanese puzzles for Cliko. It deserves to be as famous as Sudoku. It's not, and I want to fix that.

The Nikoli Legacy

Japan has a unique relationship with logic puzzles. While the West was doing crosswords, Japanese publisher Nikoli was inventing entirely new puzzle types: Sudoku (which Nikoli popularized, though Howard Garns invented it in 1979), Kakuro, Slitherlink, Hashi, and Nurikabe.

Nurikabe first appeared in Nikoli's magazine in 1991. The name comes from a spirit in Japanese folklore — an invisible wall blocking travelers' paths at night. The puzzle is about revealing which cells are wall (black sea) and which are path (white islands). I found it while building Cliko's puzzle catalog and immediately knew it needed to be in the collection.

Pure Deduction, No Guessing

You start with a grid containing numbered cells. Each number is the size of a white island — a connected group of white cells containing exactly that number. Paint all remaining cells black (sea), following three rules: every island has exactly one number and that many cells, the sea must be one connected region, and no 2×2 block of sea is allowed.

What makes Nurikabe special is how these three rules interact. The 2×2 constraint alone eliminates huge swaths of possibilities. Combined with connectivity requirements, every puzzle can be solved through pure deduction — no guessing. That's the Nikoli philosophy: fair puzzles with unique solutions.

Play Nurikabe free on Cliko Games with grids from 5×5 to 11×11. If you enjoy Japanese puzzles, try Calcudoku ZAP and Variant Sudoku.