How To Solve Nurikabe Puzzles

Solving Nurikabe Puzzles is pretty straightforward.

Nurikabe is a classic Japanese “island-building” puzzle from the same family of logic puzzles as Sudoku and Kakuro.

Nurikabe Puzzle Example

The puzzle is typically played on a rectangular grid of cells.  Some cells contain a number indicating the size of the island it is a part of. 

The basics of the game are to shade cells to divide a grid into specified-sized regions of sea and islands.

Nurikabe Puzzle Solution Example

Cells are initially of unknown color but can only be shaded or white. Two same-color cells are considered "connected" if adjacent vertically or horizontally, but not diagonally. Connected white cells form "islands," while connected shaded cells form the "sea."

The challenge is to decide if each cell is white or shaded according to a set of rules.


Common Techniques

Basic Strategy

basic strategy - Look for cells marked with “1”

Look for cells marked with “1”. Since these islands are only one cell in size, all the adjacent vertical and horizontal cells must be shaded (not diagonal).

Look for numbers that are close to each other.

Look for numbers that are close to each other. Since each number must have its own island and each island cannot touch each other (except at a corner), the cells between must be shaded.

The space to the right of the "3" must be part of that island so we can mark it with a dot. Since two islands cannot touch, the spaces above and to the left of the "4" must be shaded.

Once an island is "complete" (it has all the white cells its number requires), all cells that share a side with it, horizontal and vertical only, must be shaded.

Since all shaded cells must be connected in a single group, no shaded cell can be isolated. Look for these cells and expand them horizontally or vertically.

The space marked "2" must have a corresponding island space above or to the left of it. Since islands cannot touch, the space diagonal to the "2" must be shaded.

Look for unreachable cells. In this case, the red squares are beyond the maximum reach of any number and are shaded in.

Other unreachable cells.

WIth the rule prohibiting 2X2 shaded cells, the cells with the red dot must be islands and not shaded.

Look for areas where the correct number of island cells are already identified and shade the unneeded cells.

Look for lone island cells and fill them in.

This completes the "4" island so the two cells below can be shaded.

Finally, the two red cells are unreachable and are shaded. The cell marked with X is shaded due to the "no 2X2 rule". That leaves the cell below the "2" as the last island cell.

Sharpen your pencils and have fun!  Find more great puzzles in our catalog.