Nurikabe is a challenging and addictive logic puzzle that involves creating “islands” of white cells separated by a continuous “sea” of black cells (walls). It is a game of deduction and spatial reasoning that originated in Japan.
The Objective
The goal is to determine for every cell in the grid whether it is a “Wall” (part of the sea) or an “Island”. When the puzzle is solved, all islands must be separated from each other, and all wall cells must be connected to form a single continuous stream.
The Tools You Have
Before starting, it’s helpful to understand the components of the game:
- The Grid: A square grid (e.g., 5x5, 7x7) containing some numbers.
- Numbers (Clues): These represent the number of cells that belong to the island containing that specific number.
- Islands: Groups of white cells. Each island must contain exactly one number.
- The Sea (Walls): Black cells that separate the islands.
The Rules to Follow
Nurikabe follows four fundamental rules:
- Island Size: Each number in the grid represents how many white cells belong to that island (including the cell with the number).
- One Number per Island: Every island must contain exactly one number. Islands without numbers or with multiple numbers are not allowed.
- Continuous Sea: All black cells (walls) must be connected to each other, forming a single continuous stream throughout the grid.
- No 2x2 Wall Blocks: You cannot have a 2x2 square block consisting entirely of black cells. This is often called the “no pools” rule.
Simple Strategy
Nurikabe is a puzzle of elimination. Here are some basic strategies to get you started:
- Islands of Size 1: Any cell with the number “1” is already a complete island. All four adjacent cells (up, down, left, right) must be walls (black).
- Separate Numbers: Since two numbers cannot belong to the same island, any cell that is adjacent to two different numbered cells must be a wall.
- Avoid 2x2 Blocks: If three cells of a 2x2 square are already black, the fourth cell must be white to prevent a “pool.”
- Connectivity: If a wall cell only has one way to connect to the rest of the sea, that path must be made of walls.
- Enclose Islands: Once an island has reached its required size, all surrounding cells must be walls.
Example of Play
Imagine a 5x5 grid with a “3” in a corner.
- The two cells adjacent to the “3” could be white.
- Once you’ve marked 3 white cells for that island, you must surround them with black cells to separate them from other islands.
- You must then ensure that those black cells can reach all other black cells on the board.
Tips for Beginners
- Start by marking the cells that must be walls (e.g., between two numbers).
- Use dots (•) to mark white cells and squares (■) for black cells.
- Pay attention to the “no 2x2” rule; it’s often the key to solving difficult sections.
- Make sure your islands don’t accidentally “merge” by touching each other.
Have fun uncovering the islands!