Loomlock: one closed loop a day, and a board that refuses a guess

01  What Loomlock is

Loomlock is a free daily logic puzzle in the Nikoli slitherlink family: a grid of cells, some of them carrying a number from 0 to 3, and a single closed loop hidden in the edges between those cells. You mark an edge as a cord (part of the loop) or a stitch (definitely not), and the board is finished when your cord forms exactly the one loop the numbers allow.

Each number is a count. A cell marked 2 has the cord running along exactly two of its four sides. A 0 means the loop never touches that cell at all — four stitches, no thought required. A 3 means the cord hugs three sides and skips one. Blank cells carry no constraint, which is what makes a board a deduction rather than a lookup.

Every player gets the same board, and a new one arrives at 00:00 UTC. Boards come in three sizes and are labelled after yarn weights: Fine Thread at 6×6, Worsted at 7×7, Tapestry at 8×8. It runs in a browser, needs no account and nothing to install, and is supported by ads.

02  The one rule that does most of the work

Two constraints crack open nearly every board, and neither asks you to hold anything in your head except a parity.

At every point where the grid lines meet, the cord passes through zero edges or exactly two — never one, never three. A loop is a closed path, so it cannot dead-end at a node or cross itself there. That alone is why a stitch often reveals the next cord: rule out three of a node’s four edges and the fourth is forced by arithmetic.

The other is the clue extremes. Zeros come off the board instantly. Two 3s sitting side by side force the edge they share and the two outer edges around them, and a 3 tucked into a corner resolves to one shape with no work at all. Beginners tend to start on the 1s and 2s, which are the last things to fall; the givens are where the time is saved.

03  What the no-guess check actually does

Loomlock calls itself a no-guess puzzle and enforces it in a way few logic games do: the board holds the answer, and it refuses a mark that contradicts it. Try to draw a cord where the solution has none and the edge recoils with a quiet "can’t prove that yet". Try to stitch an edge the loop actually uses and the same thing happens. You find out that a mark is wrong in the moment you make it, not ten minutes later.

The honest flip side is that the check compares your mark to the answer, not your reasoning to your mark. A guess that happens to be right is accepted, because from the outside there is no difference between a lucky tap and a proven one. You also cannot lose. Sweep every edge of a board in cord mode — 84 of them on a 6×6 — and the board keeps the correct ones and refuses the rest, handing you a finished loop marked "no hints" and a time you would not want to post.

So the promise is narrower than the slogan, and still worth having. The board never lets you be wrong, which deletes the whole class of bookkeeping errors that makes slitherlink miserable to learn, and it makes the two numbers on your card — time and hints — a fair account of how you actually reasoned. Every board was generated offline and verified uniquely solvable by pure deduction before it shipped, so there is always a provable next step available; the block never leaves you with nothing to do.

04  A day, a month, a year of boards

The app ships with its entire puzzle bank instead of generating boards on demand: a fixed set of 380, one per UTC day, currently running from 21 June 2026 to 5 July 2027 and stepping up from 6×6 to 8×8 as the months pass. Nothing is fetched to play. The board is a pure function of the date, which is why it works on a bad connection and why two people comparing times are always comparing the same grid.

The archive is the part worth knowing about. Every past day gets a page showing that board’s finished loop drawn in full, alongside a short walkthrough built from that board’s real solution: which zero opens it, which pair of 3s forces the middle, which single edge a particular 3 leaves open. You can play any past board at your own pace. Days that have not happened yet never appear there, so the archive cannot spoil today.

05  The card, the emblem, and the streak

When the last edge closes, the cord cinches taut and you get a solve card: puzzle number, time, hints used, streak, and — when the app’s tally answers — a "faster than X% today" line. The pattern beside it is a twelve-tile sampler patch. It encodes only when in your solve you were marking, sliced into twelfths of your own clock; no tile knows where on the board you were working, so the card is safe to post next to "can you beat 3:41?".

Below the card sits the woven emblem: the finished loop drawn as a round crest, behind a gate that says plainly what it is, because unlike the card it does show the solution. It is a keepsake, never the preview image, and never shared for you.

The streak counts consecutive days you have solved and is stored in your own browser, along with your best time; replaying a day you have already finished does not inflate it. The only thing that leaves your device when you solve is an anonymous row — time, hints, streak, pace glyph — that the app’s own counter uses to work out the percentile. No account, no name, and the loop itself never goes anywhere.

06  Getting faster

A few things about the interface that are not obvious on a first board:

• Your clock starts on your first mark, not when the page loads. Reading the whole grid before you touch anything costs you nothing.
• Cord and Stitch are two modes, and a tap does whatever the current mode says. Switching costs a tap, so it pays to work in passes — one sweep of stitches, then the cords those stitches imply.
• A satisfied clue fades and gains a small tick beside it. That is your progress read-out; you never have to count a cell’s sides by hand.
• "Pull a thread" marks the next forced edge, and it picks one that continues the thread you already have rather than dropping a cord somewhere else on the board. Each one is counted on your card.
• Undo steps back a single mark. Reset clears the whole board — and does not stop the clock; only starting the board over does that.

07  Questions people ask

Is Loomlock free, and do I need an account?

Free, and no account. It runs in the browser with nothing to install and nothing to sign up for, and it is supported by ads. There is no paywall on any part of the puzzle.

What kind of puzzle is it — is it slitherlink?

Yes, it is a slitherlink puzzle, the Nikoli grid-deduction family. Some cells carry a number, each number counts how many of that cell’s four sides the loop runs along, and the answer is always exactly one closed loop that never branches, crosses itself or splits in two.

Does the no-guess rule mean I cannot make a mistake?

You cannot mark anything that contradicts the answer — the board blocks it and tells you so, which means a solve never fails on a slip. It cannot tell a lucky guess from a deduction, though, so the honest measure of a solve is the time and the hint count on your card.

Can I play past puzzles?

Yes. The archive keeps roughly the last month of boards, and every past day has a page with that board’s full solution and a walkthrough of how the deduction goes. You can play any of them at your own pace. Today and future days are never published there, so browsing cannot spoil the board you have not done yet.

When does a new puzzle appear?

A new board unlocks at 00:00 UTC every day, and every player gets the same one. Miss a day and it moves to the archive the next morning rather than disappearing.

Can I share my result without spoiling the puzzle?

Yes — the solve card is built to be posted. It carries your number, time, hints and streak plus an abstract pace pattern, and no part of it describes the loop. The woven emblem, which does show the solution, is kept separate behind a clear warning and is never used as a preview image.

08  More from the shelf

• CipherDay — Crack the cipher chain. Reveal the quote.
• Maze of Breth — Drawn by a kid. Built by robots.
• Isobath — Drop a pin. Find out how wrong you were.
• Dewkeep — Keep a creature. Grow a little world.

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