Privacy Policy
- No account, no ads, and we never sell data.
- Your progress stays on your device.
- Anonymous usage statistics are sent only if you allow it, and you can change your mind at any time in Settings.
Who is responsible
Sudoku Teacher is developed by Michal Vyroubal, an individual developer based in the Czech Republic. Contact: [email protected].
This policy covers the Sudoku Teacher app for Android, the web version at app.sudokuteacher.app and this website.
Data stored on your device
To let you continue where you left off, the app stores on your device:
- your progress: level, number of lessons, difficulty history and daily streak,
- the Sudoku you are currently solving,
- your settings (language, automatic hints) and your answer about usage statistics.
This data never leaves your device and we have no access to it. On Android it may be included in your device backup to your Google account if you have backups turned on; that backup is managed by Google, not by us. In the web version it is kept in your browser's storage for app.sudokuteacher.app. You can delete it at any time with “Start over from scratch” on the Progress screen, by uninstalling the app, or by clearing the site data in your browser.
Anonymous usage statistics (only with your consent)
When you first open the app, a switch asks whether you want to share anonymous usage data. It is off by default. If you leave it off, nothing is sent and the statistics tool is not even started. If you turn it on, the app sends the following information to help us find out whether the lessons work and where learners get stuck:
- that the app was opened for the first time, and on which platform (Android or web),
- that a lesson was started, completed or left, with its difficulty level, the rating you got and how long it took,
- which solving tricks you used and whether the move was the best one available,
- when you asked for a hint, how detailed it was and which trick it was about,
- that you opened the Full version page, from which screen and at which level, whether you tapped the Google Play badge on the web, and how a purchase ended (purchased, payment pending, cancelled, unavailable or error). The app never sees your payment details; Google handles the payment.
Along with this, the statistics tool records a random identifier created by the app, which is not linked to your name, email or any account, and basic technical details such as device type, operating system, browser and screen size. We have set the tool up not to store your IP address. We never collect the contents of your games beyond the above, any text you type, your contacts, or your location.
We use PostHog (PostHog Inc.) for these statistics, running in its EU data center in Frankfurt, Germany. The legal basis is your consent (Art. 6(1)(a) GDPR). We keep the statistics for at most 24 months.
You can withdraw your consent at any time with the switch in Settings. From that moment nothing more is sent. Because the statistics are anonymous, we cannot tell which of them came from you, so we cannot pick out and delete your past data individually.
Website and web version
This website and the web version of the app are delivered by Cloudflare (Cloudflare, Inc.). Like any web server, Cloudflare processes your IP address and basic request information to deliver the pages and protect them against attacks. Neither this website nor the web version uses cookies.
Google Play
If you install the app from Google Play, Google processes data about the download and your device under its own privacy policy. We only receive aggregated statistics from Google, such as the number of installs.
What we do not do
- No user accounts and no sign-in.
- No advertising and no advertising identifiers.
- No selling or sharing of data with third parties for marketing.
- No tracking across other apps or websites.
Children
The app is meant for anyone who wants to learn Sudoku. It does not ask for or collect personal information from anyone, including children, and usage statistics are anonymous and optional.
Your rights
Under the GDPR you have the right to access, correct and delete your personal data, to restrict or object to its processing, and to withdraw your consent. Write to [email protected]. You also have the right to lodge a complaint with a supervisory authority; in the Czech Republic this is the Office for Personal Data Protection (uoou.gov.cz).
Changes
If this policy changes, we will publish the new version here and update the date at the top.