The grid contains numbered clues. Each number is the seed of a white island containing exactly that many white cells. Shade the remaining cells black to form the river. Four rules must all be satisfied:
1. Island size: Each white island contains exactly as many cells as its number clue.
2. One clue per island: Each island contains exactly one numbered cell.
3. Connected river: All black cells form one single connected group.
4. No 2×2 black blocks: No 2×2 area may be entirely black.
Click any blank cell to shade it black (river). Click again to unshade. Right-click or long-press to mark a cell white (island). Clue cells are fixed. Nurikabe was popularised by Nikoli (Japan, 1991).
Shade a connected river around numbered islands — each island as big as its number.
The full guide, with a worked example and common mistakes: How to play Nurikabe.
Yes — only side-to-side contact is forbidden.
It is the rule that keeps the river narrow and the puzzle uniquely solvable.
Right-click or long-press a cell to mark it white (island). Click to shade it as river.