ReefwispPlay Nurikabe

How to play Nurikabe

Decide which squares are land and which are sea. The numbers are the starting cells of islands.

  1. Every island contains exactly one number. Its total number of land cells must equal that number, including the numbered cell.
  2. Land connects through sides. Different islands cannot share a side; touching at a corner is allowed.
  3. All sea cells must connect through sides. They cannot form a solid 2 × 2 block.
Completed three by three example: a size-two island at the upper left and size-one islands in both bottom corners. Five sea cells form one connected group, with no two by two sea block.2•11≈≈≈≈≈
The island marked 2 has two land cells. Each 1 is already a complete island. The five sea cells all connect.

Start beside a 1

A 1 needs no extra land. Every neighboring square above, below, left and right of it must be sea. Do not count diagonals as neighbors.

If three squares of a 2 × 2 area are already sea, the fourth must be land. Otherwise the sea would form a forbidden pool.

Mark a square

Tap a square to cycle through sea, land and unknown. Sea uses a wave symbol; unnumbered land uses a dot. Numbered cells are fixed. Finish by marking every remaining square.

The arrow buttons select a cell. Sea, Land and Clear set its state directly. Undo reverses your last change in this tab. Restart asks before clearing your marks.

Keyboard: arrows select a cell; Enter or Space cycles. S marks sea, L marks land, E or Delete clears, and U undoes. Tab moves to the next control outside the board.

Get unstuck

Hint checks all your current marks. It offers one sea or land cell that continues the solution. If a wrong mark prevents completion, it offers to clear that cell. Both actions can be undone.

Meeting every island number is not enough if the sea is split. Check sea connections and 2 × 2 areas before finishing.

Practice and Daily

Reefwisp contains 24 original puzzles: eight each at 3 × 3, 4 × 4 and 5 × 5. The first Practice puzzle is small. Daily selects from the same eight-board set at each size and changes at midnight UTC; boards repeat. Your selected daily board stays open across midnight and reloads. Use Play today’s puzzle when you want to switch.

Progress is saved in this browser. If a record is damaged or storage is blocked, the game keeps the original and explains the recovery options.

Continue in practice returns to your saved practice puzzle at this size. Next puzzle asks before leaving an unfinished practice puzzle with moves. Its saved progress stays in the collection; cycle through the puzzles to return.

Play Nurikabe →