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Puzzle Quarry

Today at Puzzle Quarry

Logic puzzles, new every day, the same for everybody who opens them. Every one of them is built and checked in your own browser before you see it.

Different puzzles, held to one standard

One of these is a grid you fill with two symbols under three rules about lines. Another is a scattering of numbered islands to be joined up. Another is a single loop traced between dots, and another a square carved into cages of arithmetic. Another is a square of numbers with inequality signs between them, and another a square of numbers to be painted out. They look nothing alike and they feel nothing alike, and the reason they are all here is that underneath they are the same kind of object: a position that one arrangement satisfies and no other does, reachable by argument.

That last clause is the standard, and it is the only promise this site makes about every board it publishes. Exactly one answer, and a route to it that never requires you to pick something at random and see what happens. Both halves are checked before a puzzle is allowed on a page — by two separate pieces of code that do not share a line, so agreeing is evidence rather than a tautology.

Difficulty means the same thing in every section as well. No puzzle here is graded by how much it hides. Each is solved by a program that always takes the cheapest move it can see, and the hardest move it was ever cornered into is the label the puzzle ships with. A board with fewer clues than another is not thereby harder, and here it is not called harder either.

Where to start

Take the binary puzzle if you enjoy reasoning along a line: counting what a row has left, noticing that two neighbours decide a third, working out which arrangements of a row survive the rules. It rewards a methodical sweep, it is very forgiving of being put down and picked up, and the smallest size is a genuine two-minute puzzle rather than a toy. Futoshiki asks much the same of you and answers in numbers instead.

Take bridges or hitori if you would rather think about shape. In neither of them are you writing a value into a cell — you are deciding what connects to what, and in both the hardest moves come from the requirement that everything ends up joined into one piece. They have a spatial, almost architectural quality that the grid puzzles do not, and people who find one kind dull are usually delighted by the other.

None of them is the harder puzzle in general — each has four levels and the top level of each will hold up an experienced solver. If you have ten minutes, the smallest size of any of them is comfortably inside it. If you have an hour and want to be beaten, the largest board at the top level of any of them will do it.

What this site does not do

There is no account, and there is nothing to sign up for. Your streak, your times and which days you have finished live in your own browser’s storage and are never sent anywhere; clearing site data for this domain deletes them permanently, and nobody here can restore them, because nobody here ever had them.

Nothing is fetched to make a puzzle. The generators run locally, which is why a board is on screen before a server-backed puzzle site would have finished its first round trip, and why every page here works identically on a train with no signal.

And no board is ever published that a person cannot finish by reasoning. That sounds like a small thing until you meet the alternative: a generator that only checks the answer is unique will happily produce grids whose one answer is reachable only by trial, and cannot tell the difference. Those get thrown away here rather than sold as a harder level, which costs generation time and is the single decision this site is built around.

Common questions

Do I need an account to play?

No, and there is nothing to create one with. Everything the site remembers about you is held in your own browser and never transmitted, so there is no login, no password and nothing to lose.

Is there a new puzzle every day for each of them?

Yes. Each puzzle type has its own daily at every size it offers, and each has its own week of difficulties, arranged so that no two of them peak on the same day.

Which puzzle should a complete beginner start with?

The binary puzzle at 6×6 on an easy day. It needs exactly two ideas, both of which can be explained in a sentence, and a first grid usually takes about two minutes.

Everything else on the site