Clues separated by one square

"Clues separated by one square" is a basic strategy in Nurikabe puzzles. This technique builds on the primary rule of Nurikabe, which stipulates that all islands must be separated by at least one wall.

Therefore, when two clues are found in the same row or column and there is only one square between them, it can be safely assumed that the square in the middle must be a wall. This square effectively serves to separate the two islands that are associated with the two clues.

This is how the technique is used in practice:

Using the "Clues separated by one square" technique is a simple but effective way to make progress in a Nurikabe puzzle, allowing you to easily identify wall squares that must exist to separate islands.