Separate islands from the sea using pure logic. Each number defines an island — the rest is ocean. No guessing required.
Gentle — 5×5
Nurikabe is a binary-determination logic puzzle played on a rectangular grid. Some cells contain numbers; these are the seeds of islands. Your goal is to determine which remaining cells are island (white) and which are sea (black). The puzzle is fully solvable through deduction alone — no trial-and-error needed.
Each numbered cell anchors an island: a connected group of white cells whose size equals the number. Every island contains exactly one number. All sea cells must connect into a single contiguous body, and no 2×2 square can be entirely sea. Start by marking cells that obviously must be sea (between islands that cannot connect) or island (cells needed to reach the required size). As you fill in more cells, logical chains reveal the rest.
Three rules govern Nurikabe: (1) Each numbered cell belongs to an island of exactly that many connected white cells. (2) All sea (black) cells form one connected group. (3) No 2×2 area is entirely sea. Islands connect horizontally and vertically but not diagonally. Every puzzle has a unique solution reachable by logic alone.
No. Every puzzle on whatifs.fun is hand-crafted with a unique solution that can be reached through logical deduction. If you feel stuck, look for cells that must be sea to prevent two islands from merging, or cells that must be island to reach the required count. Enabling error checking can help spot contradictions early.
There are over 40 hand-crafted puzzles across four difficulty bands: Gentle (5×5), Moderate (7×7), Tough (7×7 and larger), and Diabolical (10×10). Each puzzle has been verified to have exactly one solution. New puzzles are added regularly.
Last updated: April 2026