Nurikabe: An Island With One Way to Grow

An island still short of squares, with only one square it could grow into, grows there. Dot that square: it’s part of the island.

This is one of the Nurikabe techniques. Each page shows its technique on the same 8×8 from the game, Medium level 8.

The rule

1. Find an island that still needs squares.
2. List the empty squares touching it.
3. If there’s only one, it’s island.

In a real puzzle

On the 8×8, it’s first needed at step 21. The 2 in row 3, column 2 still needs a second square, and walls now surround it on every side but one: below it. So it grows down into row 4, column 2.

How often you’ll need it

On 41 of the 50 Easy levels, 48 Medium and 49 Hard: 1.7 times per Easy level on average, 2.5 on Medium and 3.4 on Hard. It’s 2 of the 42 steps on the 8×8 here.