Nurikabe is a logic puzzle ("nurikabe" in Japanese folklore is an invisible wall that blocks roads and upon which delays in foot travel are blamed; other names for the puzzle: "Cell Structure", "Islands in the Stream"). The puzzle is played on a grid, typically rectangular with no standard size. Some cells of the grid start containing numbers.

The goal is to determine whether each of the cells of the grid is "black" or "white" according to the following rules:


Cross+A can solve puzzles from 3 x 3 to 30 x 30.

Pairs Nurikabe: each island must contain exactly two numbers (instead of one) and have total size equal to the sum of these numbers.

Pairs Nurikabe