How to play Lighthouses
Place one-square boats so each lighthouse counts the boats in its row and column; boats never touch and are always in sight of a lighthouse. Also known as Boats and lighthouses.
The rules
- Each boat fills one square of sea.
- A lighthouse number counts the boats in its whole row and its whole column together.
- Boats never touch each other or a lighthouse, not even at a corner.
- Every boat is in the same row or column as at least one lighthouse.
Playing Lighthouses on Puzzle Solvers
- Choose a grid size and difficulty, then press New Puzzle.
- Tap or drag to place boats; use the Sea tool (or right-click) to mark squares that are only water.
- A lighthouse number counts the boats in its row and its column together.
- Boats never touch each other or a lighthouse — not even at a corner — and every boat is in line with a lighthouse. Hint explains the next square.
A worked example
A lighthouse shows 0, so its row and column are all sea. Another shows 1 and, after crossing out the sea squares, only one square in its row and column is left — that is a boat.
The boat’s eight neighbours become sea, which often finishes another lighthouse’s count.
Strategies
- Zeros first. A 0 lighthouse means its whole row and column are sea.
- Around the lighthouse. The eight squares around a lighthouse are always sea.
- Out of sight. A square no lighthouse can see along a row or column is sea.
- Full counts. If a lighthouse needs as many boats as it has possible squares left, they are all boats.
- Boat neighbours. Once you place a boat, its eight neighbours are sea.
Common mistakes
- Counting only the row, not the column too.
- Letting two boats touch at a corner.
Where it comes from
Lighthouse puzzles are a well-loved relative of ship-finding puzzles. This version was made for this site and always has one answer.
Frequently asked questions
Do lighthouses block each other’s view?
No — a lighthouse counts every boat in its whole row and column.
Are all boats one square?
Yes — every boat here fills exactly one square.
Is there always one answer?
Yes — every puzzle is checked so that logic alone finds every boat.
Keep going
- Play Lighthousesa fresh puzzle every time
- Fleet FinderPlace the whole fleet so that each row and column has the right number of…
- TentsPitch a tent beside every tree — one each — so no two tents touch and every…
- Hidden SnakeFind the snake — one unbroken line from head to tail — using the row and…
All guides: How to play every puzzle and game.