Why one puzzle a day and not an endless supply

Chain gives you one puzzle a day and no way to ask for another. That is the whole design, and it is not a supply problem — we could generate a thousand boards a minute. The single daily puzzle does three things an endless list cannot: it ends the session for you, it makes everyone's result mean the same thing, and it keeps the whole commitment down to a few minutes. What it does not do is make you smarter, and the part of this page we care most about is the part where we say so plainly.

The session ends whether or not you decide to end it

A feed is built so there is always one more. That is not an accusation, it is just the shape of the thing: infinite supply plus a ranking that learns what keeps you scrolling means the only stopping rule is yours, and yours has to work while you are tired.

Chain has an empty shelf instead. Three moves on Monday and Tuesday, four on Wednesday, Thursday and Sunday, five on Friday and Saturday. You reach the target, the result card appears with your tries and your time, and there is nothing else to press. No next puzzle, no queue, no "since you liked that one". Tomorrow's board does not exist on the page and cannot be requested early.

The useful part is that stopping costs you no willpower at all. You did not resist anything; there was nothing there. We think that is a much better mechanism than a screen-time warning, because it does not depend on how you are feeling at 11pm.

Everyone is looking at the same board

There is one puzzle per calendar day and it is the same for everybody. The day turns over at midnight in your own timezone, so a player in Tel Aviv and a player in Lisbon get the same start number, the same target and the same hand, just at different wall-clock moments.

That single fact is what makes a result worth sending to someone. If the puzzle were generated per person, "three tries, four minutes" would be a number about nothing. Because the board is shared, it is a claim you can check yourself, and the disagreement is interesting: on Sunday 13 September the target was 386 from a start of 41, and the whole day comes down to whether you spotted that the additions cap out at 202 and the swap has to do the rest. Two people who both solved it in one try may still have found completely different routes into it.

The share text is three lines of plain text: the date, whether you solved it, your tries, your time, and the site address. Not a picture of the board, not a grid of coloured squares, nothing that gives away a tile. You can paste it into any chat without spoiling anyone, which is the only reason we let it be copied at all. The how to play page shows exactly what it looks like.

The other half of "same board" is the stats page, where you can see what the day did to everyone else: how many people solved it, the share who did it in one try, the median tries and the median time. That aggregate is withheld entirely until at least five people have solved the day, because "one solver, one try, 1:40" is a description of one identifiable person, not a statistic.

A few minutes is a small enough thing to agree to

We time ourselves loosely and the numbers are honest: a minute or two on Monday and Tuesday, three to five on the medium days, and somewhere around ten before we stop feeling bad about Friday and Saturday. That is the entire daily cost.

Anything that wants a slot in your day has to be small enough that a bad day does not knock it out. A forty-minute puzzle is a hobby and needs to be scheduled. A three-minute puzzle survives a delayed train. We tune the difficulty bands so that the hard days stay hard without becoming long: the strategy guide exists partly so a Saturday costs you ten minutes of thinking rather than forty minutes of shuffling tiles at random.

What we will not tell you: that this makes you sharper

Daily puzzles are usually sold as brain training, and we are not going to do that, because the evidence does not support it.

The most careful review of the field we know of is Simons and colleagues in Psychological Science in the Public Interest in 2016. Its conclusion, in its own shape: brain-training tasks do improve performance on the trained tasks; there is less evidence that training improves performance on closely related but non-identical tasks; and there is very little evidence that it improves performance on distantly related tasks or improves everyday cognitive performance. The gap between "you got better at the game" and "you got better at your life" is where nearly every commercial brain-training claim lives, and the review is clear that the gap has not been demonstrated.

Regulators have taken the same view of the marketing. In January 2016 Lumos Labs agreed to pay $2 million to settle US Federal Trade Commission charges of deceptive advertising for Lumosity; the FTC's position was that the company had preyed on fears of age-related decline and simply did not have the science to back up its ads.

So here is our claim, and it is the only one we will make: playing Chain every day will very likely make you better at Chain. We have no evidence that it does anything else, we have not measured anything, and if a site tells you that a few minutes of arithmetic protects your memory, it is selling you something. The honest case for a daily puzzle is that it is an enjoyable few minutes with a clear end. We think that is enough, and it is the whole reason the site exists.

What a puzzle has that a feed does not

Some of the difference is structural rather than motivational.

• There is one right answer. Exactly one set of tiles reaches the target in the required number of moves, and that uniqueness is checked by the generator before a puzzle is ever published. When you land on the target, you are done being uncertain — a rare feeling online.
• The difficulty is decided by the weekday, not by you. Easy Monday, hard Saturday, the same curve for everyone. Nothing adapts to keep you engaged, because nothing is watching how engaged you are.
• Losing is bounded. A wrong chain is a try. The board resets, the tiles come back, the counter goes up by one, and the near miss is usually within ten of the target, which tells you the mistake is one tile rather than the whole plan.
• There is no supply to tune. The thing that makes feeds hard to leave is that the next item can always be a slightly better one. A single board a day removes that lever entirely, from us as much as from you.

Why there is an archive at all

We did build an archive — every past day, replayable, with a written walkthrough of the solution underneath. That obviously cuts against scarcity, so it is worth being straight about how we resolved it.

Nothing you do in the archive is recorded. Playing an archived board does not touch your streak, does not appear in your stats, does not send a result, and does not mark the day as solved. It is the same board and the same rules with nothing attached. That was deliberate: we wanted the back catalogue available for curiosity — you liked a puzzle, a friend mentioned Tuesday, you want to see how the hard Friday from 11 September actually worked — without turning it into a pile of unplayed content with a score attached to it. If the archive counted, the site would immediately become a backlog, and backlogs are the thing we were trying to avoid.

When it is not worth your few minutes

Some days the puzzle will not give and you will not be in the mood to make it. Skip it. The streaks page goes into why a broken run is not a reason to stop, but the shorter version is that a daily puzzle you resent is worse than no daily puzzle. Come back on an easy Monday.

If you have not played before, how to play has the rules and four worked puzzles, and strategy is where we explain how we find the set quickly. Both take longer to read than today's board takes to solve.