Nurikabe ぬりかべ
Nurikabe uses an island-and-sea metaphor: numbered white islands must reach the correct size, separated by a single connected black sea. No 2×2 black blocks allowed. The name comes from a folklore creature—an invisible wall that blocks night travellers—a perfect fit for the puzzle's constraint.
Rules
Each clue number is an island seed: the white cells connected to it must total exactly that many cells. Each island has exactly one number. All black cells form one connected region (the sea) with no 2×2 black blocks. Non-clue white cells must connect to some clue. Solve by logic; unique solution. Key strategies: two adjacent 1s must have a black cell between them. A 1 is already complete—place black cells around it. Use the no-2×2 rule to force connections and isolate islands.
History
Creator "renin" published Nurikabe in Puzzle Communication Nikoli #33 (March 1991). The nurikabe folklore creature—a wall blocking travellers—gave the puzzle its name. Nikoli has published it in every issue since. One of Nikoli's "big four" alongside Sudoku, Slitherlink, and Kakuro. Global puzzle app ecosystem.
Tips for beginners
Isolate large islands first—they constrain the most cells. Any white group unreachable by any clue must be black. Prevent the sea from splitting: ensure black connectivity at every step. Two adjacent 1-clues force a black cell between them. Use the no-2×2 rule to deduce where black cells cannot go.
Cultural context
Nikoli flagship puzzle; nurikabe folklore as perfect metaphor. Published in every Nikoli issue since 1991. Strong global puzzle app presence. The nurikabe is a folklore creature—an invisible wall that blocks night travellers—a perfect fit for the puzzle's island-and-sea constraints. One of Nikoli's "big four" alongside Sudoku, Slitherlink, and Kakuro. Play free at Nikoli.com, Conceptis Puzzles, and Simon Tatham's Portable Puzzle Collection.
Play online
Play free at Nikoli.com, Conceptis Puzzles (conceptispuzzles.com—Nurikabe), Puzzle-Nonograms.com, and Simon Tatham's Portable Puzzle Collection. Mobile apps: Conceptis Nurikabe, Nikoli puzzle collections, and various logic puzzle apps.
Where to Buy or Play
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- 📖 Nurikabe Puzzle Book (Nikoli) Official Nikoli nurikabe puzzle collection
- 📱 Play Nurikabe free online Free daily Nurikabe puzzles with multiple difficulty levels