Sudoku Istind

A quiet sudoku for iPhone. No ads, no accounts, no tracking, and nothing that nags you from a notification.

Istind is built around one idea most sudoku apps get backwards: the app should not do the thinking for you. A digit that breaks a rule is marked, because that is a rule and not a judgement. A wrong digit that still fits is left alone — finding it is part of the puzzle, exactly as it is on paper.

A COACH THAT EXPLAINS INSTEAD OF ANSWERING
Stuck? The coach walks the next logical step in four stages: where to look, what the evidence on the board is, why it follows, and only then the move itself. Stop at any stage and take it from there. Nothing is locked, deducted or scored for using it.

A PUZZLE CHOSEN FOR WHAT YOU ARE LEARNING
Once you have finished a board, Istind can offer one whose solving path uses the technique you are next in line to learn — and the coach teaches it as you go.

THE SAME BOARD AS EVERYONE ELSE, ONCE A DAY
The daily puzzle follows a weekly rhythm from Easy on Monday to Expert on Saturday. Miss a day and the archive lets you play it later — it fills the calendar, but it will not repair your streak.

SIX LEVELS, ENDLESS PUZZLES
Every board is generated on your iPhone and verified to have exactly one solution. Nothing is downloaded, so it works with no signal at all.

Notes, undo, conflict highlighting, full VoiceOver support, Dynamic Type, and a light and dark paper design made to be easy on the eyes late at night.