Island Sea is a shading puzzle. The grid starts white with a few numbers on it. You paint cells as sea until every number sits on its own island of the right size and the water flows as one body. Every puzzle here is generated fresh and checked by a solver so that it has exactly one answer.
How to play
The rules.
- Each number marks an island: a group of white cells connected by their sides, with exactly as many cells as the number. Every island contains exactly one number, and every white cell belongs to an island.
- Islands never touch each other by a side (touching at a corner is fine).
- All sea cells form one connected body, again connected by their sides.
- No 2×2 block may be entirely sea.
Marking cells. Tap a cell to cycle through three states: sea, a dot (meaning “this stays island”), and empty again. You can also select a cell and use the ■ Sea and · Island buttons, or Erase. On a keyboard, X or B paints sea, the full stop places a dot, and Backspace clears; the arrow keys move between cells.
Dots are only notes for yourself. The puzzle counts as solved the moment every sea cell is painted, whether or not the remaining cells are dotted.
Mistakes and help. A 2×2 block of sea is highlighted, and so is a white area that joins two numbers or has grown past its number. A number is highlighted when the sea around it leaves too little room for its island. Hint fixes a wrong sea cell if you have one, otherwise it paints one correct cell. Undo takes back your last change. The timer and the number of hints you used appear when you finish.
Difficulty. Choose under Difficulty at the top; New puzzle creates another grid at that size.
| Level | Grid | Largest island |
|---|---|---|
| Easy | 7 × 7 | 4 cells |
| Medium | 10 × 10 | 4 cells |
| Hard | 12 × 12 | 4 cells, a bigger sea to connect |
Strategy
Start with the 1s. An island of size 1 is complete, so all four cells around it are sea.
Separate neighbouring numbers. Two numbers that are two cells apart in a line cannot share the cell between them, because islands may not touch: that cell is sea. The same goes for a cell that touches two different islands.
Watch the 2×2 rule. Whenever three cells of a 2×2 block are sea, the fourth is island. This rule fills in a surprising number of cells late in the puzzle.
Keep the sea flowing. A patch of sea that is about to be cut off from the rest needs an exit; the only cell that can keep it connected must be sea. Likewise an island that has only one way to grow must grow there.
Count the unreachable cells. A white cell that no island can reach within its remaining size has to be sea.
If you enjoy Island Sea, try Kakuro or Killer Sums next.
