The Daily Slitherlink

Today’s loop, at any size from 5×5 to 12×12. It is grown from today’s date, which is why yours and everybody else’s are the same board.

Your record

• —Current streak
• —Longest streak
• —Days played
• —Best time, this size

A date, and no server behind it

Nothing is fetched to make this puzzle. The calendar day is turned into a number, that number drives every decision the loop builder makes, and the same number therefore draws the same curve on any machine running this code, anywhere, without those machines ever comparing notes. There is no puzzle-of-the-day sitting on a server waiting to be handed out, because there is no server.

The consequence worth being straight about is that tomorrow already exists and anybody willing to move their clock forward can play it. No secret is being kept and pretending otherwise would be theatre. What the arrangement buys instead is real: the board is on screen before a networked competitor would have finished asking permission, and it works identically on a train with no signal.

It also makes every past day permanently reachable. A link to a Thursday in March opens the exact loop people were drawing that Thursday, years later, on a computer that has never contacted this site.

What your browser is doing while the board appears

Rather more than you might expect. A loop is grown as a region of squares that is stirred at random until its outline is interesting, the numbers are read off that outline, and then the numbers are carved away one at a time for as long as the reasoning solver can still finish without them. Only then is the result graded, and a board that landed outside the day’s difficulty is discarded and the whole thing started again.

On a modern phone that is a fraction of a second, and on a 12×12 it is a couple of hundred milliseconds of genuine work in a background thread so the page never stalls. It does mean today’s board may be the third one your browser built and the first two were thrown away — which is the price of a label that means something.

None of it is cached anywhere but in your own machine, and none of it is reported. The only trace this page leaves is in your own browser’s storage, and only if you finish.

The week, the clock and what a hint costs

Difficulty follows the weekday, read in UTC so everybody turns the page at the same moment. Monday and Wednesday are the gentle days here, Thursday is the wall, and the weekend sits in between. That shape was chosen against the other two puzzles rather than copied from them — somebody who plays all three should not meet three walls on the same morning.

Finishing any one size records the day. Playing all five does not record five, there is no table to climb, and the number is only a record of having turned up, which is the only honest thing a daily can measure about anybody. Size is an independent choice: a 12×12 easy board is a long sit rather than a hard one.

A hint names the argument it used and links to the page that explains it, so taking one is the site working rather than a failure. It does not break a streak, and it is not hidden in the share text either — the result you copy says how many you took, because a time set with four hints and a time set with none are different results.

Common questions

More Slitherlink pages

• SlitherlinkUnlimited boards
• Slitherlink rulesThree rules, in full
• Solving a loopA 6×6, worked
• Loop techniquesThe whole ladder
• Squares and dotsTechnique — easy
• The corner casesTechnique — medium
• Threes togetherTechnique — hard
• Closing too earlyTechnique — expert
• Guessing at loopsTechnique — refused, here too
• Printable slitherlinkFor paper
• Slitherlink archiveEvery past loop