The short version
- As a guest, your practice stays on your phone. We don't receive it.
- If you save your progress to an account, we store it so you can use it on another phone.
- We don't show ads, sell data, or track you across other apps and websites.
- You can delete everything yourself, anytime, in the app.
Who we are
Mental Math Crow is a free, non-commercial project by Julian Geselle. There are no ads, no paid features and no tracking. Julian is responsible for the data described here, and you can reach him at [email protected].
What's stored on your phone
To work, the app keeps the following on your phone, for everyone:
- Your answers and how long they took, which facts and strategies you know, and your streak.
- Which shortcuts you found easier, and your favourite strategies.
- Your settings: goal, reminder time, haptics, language.
- The name you chose, if you entered one, and your crow avatar.
As a guest, none of this leaves your phone. Reminders are scheduled on the phone itself, so they don't go through our servers either.
What we store if you save your progress
When you save your progress to an account, we store:
| Sign-in details | Your email address, or the identifier Apple or Google gives us when you sign in with them. With Apple you can choose to hide your email, and we'll only see a relay address. |
|---|---|
| Your progress | Everything listed above, so it can be restored on another phone. |
| Age check | Whether you said you're old enough for an account where you live. We don't ask for your birthday. |
We use this to run your account, keep your progress in sync, and send you sign-in codes. We don't use it for advertising or profiling.
Legal basis
If you're in the EU or UK: we process your account and progress to provide the service you asked for (Article 6(1)(b) GDPR). Notifications only happen if you allow them on your phone.
Who helps us
We use a small number of service providers. They only process data on our behalf and under data processing agreements.
| Supabase | Hosts accounts and the progress database. Data is stored in Switzerland (Zurich). |
|---|---|
| Resend | Sends the emails with your sign-in code. |
| Apple and Google | Only if you choose to sign in with them. Their own privacy policies apply to that sign-in. |
Where a provider processes data outside the EU, it's covered by the EU Standard Contractual Clauses or an adequacy decision.
Children
Anyone can use Mental Math Crow as a guest. Before an account is created, the app asks whether you're old enough for one where you live (for example 16 in Germany and 13 in the US). If you're younger, your progress simply stays on your phone, and nothing is sent to us.
How long we keep it
- Account data is kept until you delete your account.
- When you delete your account, your data is removed from our live database straight away, and from backups within 30 days.
Your choices and rights
- Delete: in the app, open Profile & settings and choose Delete account and data.
- Correct: change your name and settings in the app anytime.
- Get a copy: email us and we'll send you your data in a common format.
- Object or restrict: email us if you disagree with how we use your data.
You can also complain to your local data protection authority.
Changes
If we change how we handle data, for example by adding anonymous usage statistics, we'll update this page before the change takes effect and show the new date at the top.
Contact
Questions about privacy go to [email protected].