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Asked mostWhy doesn't it tell me a number is wrong?

Because that is the puzzle. Istind marks a digit that breaks a rule — the same number twice in a row, column or box — since that is a rule and not a judgement. A digit that is wrong against the solution but still fits the rules is left alone, exactly as it would be on paper. Finding your own mistake is part of solving, and an app that removes it removes the reason to be careful.

If you have lost the thread completely, the coach will get you back on track without telling you which cell was wrong.

Four stepsWhat does "I'm stuck" do?

It does not fill in the answer. The coach walks the next logical step in four stages: which cell or region to look at, what the evidence on the board is, why that evidence forces the conclusion, and finally the move itself. You can stop after any stage and finish the reasoning yourself — most people find the first or second stage is enough.

Using the coach is never punished. It is counted, so the statistics can honestly say which techniques you have completed a board with and without help, but nothing is locked, deducted, or scored.

Same for everyoneThe daily puzzle

Everyone with the same app version gets the same board on the same day, and the difficulty follows a weekly rhythm: Easy on Monday and Tuesday, Medium midweek, Hard on Friday, Expert on Saturday, and Medium again on Sunday. Missed a day? The archive lets you play any earlier date. A board played from the archive fills the calendar but does not repair the streak — a streak you can buy back afterwards would not mean anything.

Chosen for youOne step beyond

Once you have completed a board, the home screen may offer a puzzle chosen because its solving path uses the technique you are next in line to learn — the lowest one you have not yet completed a board with unaided. The coach is there to teach it as you go. The card disappears when there is nothing left to offer, and it never claims that you have mastered anything: the app can see which boards you met, not how you solved them.

OfflineDo I need a connection?

No, and there is nothing to sign in to. Puzzles are generated on your iPhone, so the app works identically in a basement, on a plane, or with the phone in airplane mode. See the privacy page for what that means for your data.

Is my progress backed up?

No. History lives only on your device, and deleting the app deletes it. That is the honest cost of having no account and no server. If a backup or sync ever gets added, it will be optional and it will be described here first.

Last updated 26 July 2026.