Lighthousedle
Eight scored columns, including focal height and the range of the light
Lighthousedle has the widest grid in the family: eight columns scored on every guess, two of which are numbers a navigator would actually use. You get six tries and no picture at all.
Eight columns, six guesses
Name any lighthouse in the pool and the row fills with its country, continent, build decade, height bracket, construction material, heritage status, focal height and the range of its light. Country, continent, material and heritage match or they do not. Build decade, focal height and range are numbers with an arrow pointing towards the answer.
Tower height is the odd one out: it is scored as a bracket, so it matches exactly or not at all. A lighthouse with no recorded height reads unknown, like any other gap.
Focal height and range
Focal height is the height of the light itself above sea level, not the height of the tower, which is why the two columns disagree so often. A short tower on a headland can carry its light far higher than a tall tower on a sandspit.
Range is how far the light is charted as being visible, in nautical miles. Between them, the two columns are the closest thing here to reading a light list: they tell you what a lighthouse is for rather than what it looks like, and once you start using them the grid narrows a great deal faster.
The data and its gaps
All 1,178 lighthouses come from Wikidata under CC0 1.0, frozen into the game. Where the record carries no material the cell says unknown rather than guessing at stone or iron, and unknown is common enough in this pool to be worth reading as information in itself.
The calendar runs 1,007 days. Europe and North America dominate the pool, which is a fact about who has kept lighthouse records rather than about where lighthouses stand.
After the round
The reveal quotes a short verbatim extract from the lighthouse's English Wikipedia summary under CC BY-SA 4.0 and links back to the article. Two bonus rounds follow, asking which of two other lights was built later and which one stands in a named country.
The thing that stays with you is the vocabulary. A granite tower from the 1850s with a focal plane forty metres up and a light charted at eighteen nautical miles becomes a sentence you can picture, and coastlines read differently afterwards.
Questions
What is focal height, and why is it a separate column?
It is the height of the light above sea level rather than the height of the structure. A squat light on a cliff can sit far higher, and throw further, than a tall tower on a flat shore, so the two columns often move in opposite directions.
Is it the same puzzle for everyone?
Yes. One lighthouse a day, the same for every player, rolling over at midnight UTC, from a calendar built in advance rather than drawn at random.
Do I need an account?
No. There is no login. Your streak and your stats are kept in your browser's local storage.