Nurikabe Generator

Printable Nurikabe Puzzles: Islands in the Sea

Nurikabe is a Japanese shading puzzle in which numbered cells mark white islands and every other cell is shaded into a single black sea. The numbers tell you exactly how big each island is, and the deductions that flow from those clues make Nurikabe one of the most elegant pencil-and-paper logic puzzles ever invented.

This generator produces print-ready Nurikabe puzzles in A4 or US Letter PDF format, with two puzzles per page on a friendly grid (5x5, 7x7 and 9x9 are supported). A separate solution page is optional. Nurikabe is a superb quiet-time activity, travel puzzle, puzzle-club handout and brain-training routine for teenagers and adults.

Unlike Sudoku, Nurikabe has no arithmetic. It is pure spatial deduction: you reason about which cells must be white, which must be black, and how the no-pools and connectivity rules force your hand. Every clue radiates constraints across the board.

How the Nurikabe rules work

You begin with a grid containing a few numbered cells. Your job is to shade some cells black according to four rules.

• Each numbered cell is part of exactly one white island, and the number equals the island's total cell count.
• Every island contains exactly one number; islands never touch each other orthogonally (corners are fine).
• All black cells form one orthogonally connected sea.
• The sea may never contain a 2x2 block of black cells, a rule solvers call "no pools".

The four rules interlock. A clue of 1 means its cell is the entire island, so every neighbour must be black. The no-pools rule then ripples outward, and the connectivity rule keeps the sea from ever being split in two.

Who Nurikabe is for

Beginners

Start with the 5x5 grid. With fewer clues to track, you can learn the core moves: walling off clues of 1, and joining a clue to its only possible expansion direction.

Puzzle enthusiasts

The 9x9 grid offers chains of deduction that rival a hard Sudoku, with the bonus that no two Nurikabe solves ever feel the same.

Classroom teachers

Nurikabe builds spatial reasoning and logical proof without any arithmetic load, which makes it ideal for a mixed-ability puzzle club.

Parents

Print a page for a long journey. The tactile satisfaction of shading the sea around tidy white islands keeps children engaged for ages.

What you can customise

• Grid size: 5x5, 7x7 or 9x9.
• Puzzle count: one to four, laid out two per page.
• Include solutions: toggle a second page with the sea shaded black.
• Seed: reproduce the exact same set on demand.
• Paper size: A4 or US Letter PDF output.

Worked example

Suppose a clue of 1 sits in the middle of the grid. An island of size 1 is complete on its own, so all four orthogonal neighbours must be black. That single deduction immediately paints four sea cells and often forces nearby cells too.

Now imagine two clues diagonally one cell apart. The cell that touches both islands orthogonally cannot belong to either (islands must not touch), so it must be sea. Chains of these "between two clues" deductions are the backbone of Nurikabe solving.

How to use the tool

1. Choose a grid size of 5x5, 7x7 or 9x9.
2. Pick how many puzzles to place in the PDF.
3. Decide whether to include the solutions page.
4. Optionally set a seed for a repeatable set.
5. Select A4 or US Letter paper, then click Download and print at 100% scale.

Methodology

The generator grows several disjoint white islands from random seed cells, keeping each island separated from its neighbours, then treats every remaining cell as sea. It validates that the resulting sea is one connected region and contains no 2x2 pool, retrying with a fresh seed until a legal board is found. The printed solution shades that sea. In v1 some boards may admit more than one valid shading; the printed answer is one valid solution.

Tips for solving

• Wall off every clue of 1 first; all four neighbours are sea.
• A cell between two different clues that touches both is always sea.
• Watch the no-pools rule: if three cells of a 2x2 block are black, the fourth must be white, which often completes an island.
• Keep the sea connected. A shading that would trap a pocket of sea is illegal.

Designed for A4 and US Letter printing

The PDF prints cleanly on both paper sizes. Two puzzles per page keep every clue readable and leave room to shade the sea firmly with a pencil or marker.

Why Nurikabe is a satisfying form of brain training

Nurikabe rewards patient, global thinking. A clue on one side of the board can constrain a cell far away because the sea must stay connected and pool-free across the whole grid. That long-range reasoning is exactly the kind of disciplined logic that puzzle fans find so absorbing, and it is why Nurikabe sits alongside Sudoku and Slitherlink as a modern classic.

Because the puzzle has no arithmetic, the difficulty comes entirely from deduction, making each solve a clean exercise in logical proof. Once the final island is sealed off and the sea flows unbroken, the board snaps into a single satisfying picture.

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