A deduction game whose every case is generated, and then proven, before you ever see it. Free, in your browser, no account, no install.

You keep a lighthouse on a bad coast. Six vessels pass in the dark and each one is hiding what she is. You learn what you learn from where you point the lamp, because the beam lights one arc at a time and the haar takes the rest.

Make your number is what a ship does when she identifies herself by hoisting her code letters. Your job is to make theirs.

The loop

A night is a set of berths and a set of categories: rig, cargo, home port, and the two flags she flies as her number. Every category is a permutation across the berths, so exactly one vessel is the barque, exactly one is carrying salt, exactly one is out of Whitby.

You have a fixed number of sweeps. Train the lamp on a bearing, sweep it, and whatever is out there writes you one line in the log: "the one carrying lime was the ketch", "there were three vessels between the Appledore boat and the vessel flying QH."

The bearing board tells you which bearings are holding something. It never tells you what. Point the lamp at an empty bearing and you have spent a sweep for nothing.

Three things the game promises, and how they are enforced

Every one of these is proved by machine before a night is dealt to you:

  • Exactly one answer. The generator draws a solution, builds the full clue pool and refuses the night unless the solver reads back exactly one reading. There is never a second answer that also fits.
  • No guessing, ever. A night must be closable by elimination alone. Anything that would need you to assume something and check it later is rejected outright.
  • Every clue is load bearing. Once a night qualifies, clues are stripped away one at a time for as long as it still qualifies. Nothing you are given is decoration.

The third image on this page is not a claim about that. It is the output of it: the generator and the solver are re-run while that picture is being built, and the numbers printed on it are whatever came back. The last build read 120 nights generated across 4, 5 and 6 berths, 120 uniquely solvable, 120 closable by elimination alone.

The second system: the lamp decides which evidence you get

Difficulty here is not a timer and it is not a bigger grid. It is how much evidence has been withheld, and where the lamp lets you go looking for it. The generator minimises a night until it sits on the edge of solvable; the lamp then decides which of that minimal set you actually collect. A hard night is one where pointing the lamp wrong costs you the only observation that could have closed the case.

The haar can take an observation before you read it. It never destroys one: it moves it to another bearing, and it is still out there.

The lantern room

Five fittings, bought with what the Board pays you, and every one changes which evidence is reachable rather than how fast you can act.

  • A catadioptric lens — the beam lights the sector either side of the one you train it on.
  • A mercury bath — one more sweep every night.
  • A fog signal — the first observation of a night can never be taken by the haar.
  • A tide table — one vessel's berth is known before the first sweep.
  • A better glass — every bearing shows how many observations it is holding.

Losing, and never starting over

A wrong name costs you the night, never the run. You keep what the Board paid you and every fitting in the lantern room, and a fresh night takes its place.

Close the tab whenever you like. A night is rebuilt from its seed, which is pure, and your observations are replayed onto it, so nothing is lost and nothing has to be repeated.

Drawn by the game

No font file, no image model, no asset pack. Six seamless material plates, forty signal flags (the alphabet of the International Code of Signals, plus its numeral pennants and substitutes) and eight rigs drawn as continuous outlines in two lighting states each, all generated from one shape language. The lighthouse and its lens are drawn in code at run time. The last image on this page is the whole set on one sheet.

The audio is six cues and a thirty second theme, rendered from authored scores. Every sample is arithmetic. No sample library, no model.

Controls

Click a bearing, or the left and right arrow keys, to train the lamp. Sweep spends one. The log (or L, or Tab) opens the grid: click a cell to rule it out, right click to pin one. Call it when you are ready to name the berths. M mutes.

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More information

Development log