Last updated: November 2026
This privacy policy applies to the app Ixilotl and to the website ixilotl.de (see the sections "This website" and "Contact by email and beta requests" below).
The data controller within the meaning of the General Data Protection Regulation (GDPR) is:
Sebastian Buhl
Rheingoldstr. 5
65203 Wiesbaden
Germany
Email: support@ixilotl.de
See also our legal notice.
Ixilotl stores the game state locally on the device: learning progress (every task with answer times and results), settings, and the name entered in the game. Learning progress and the name never leave the device and are not shared with third parties. Some settings are transmitted as usage data – only with consent (see below).
No cloud backup: The app is excluded from Android device backup. The game state is therefore not backed up to your Google account, and uninstalling the app deletes all of its data from the device.
Note for users of early test versions (before November 2026): If device backup was switched on, these versions could store the game state encrypted in the Android backup of your Google account and save an “early user” flag (without name or learning data) in Google Block Store. The current app deletes the Block Store entry automatically on its next start. You can delete an older device backup in your Google account settings (Google Drive → Backups).
The app additionally uses Firebase Crashlytics and Firebase Analytics (see below). There is no user account and no chat feature. The app shows no advertising – neither personalized nor of any other kind.
The app uses Firebase Crashlytics and Firebase Analytics (Google LLC) to detect crashes and understand how the app is used, so we can improve it. This may transmit the following information:
This data is not linked to a user account (there is none) and contains no information that allows direct identification of a person. There is no personalized advertising and the device's advertising ID is not used for this purpose.
This data is only collected if a parent has given consent beforehand, separately
for each of the two services (see "Consent by parents"). Without consent, Firebase is not started in
the app at all.
More information: firebase.google.com/support/privacy
On first launch (or once after the update) the app asks in the "For parents" area whether the two data shares are allowed. The child is asked to hand the device to a parent; before the question there is a quick check for adults (entering the date of birth, which is not stored). Parents can allow usage statistics (Firebase Analytics) and crash reports (Firebase Crashlytics) separately; both are off by default. "Allow none" or "Later" keeps everything off – the app then works without any restriction.
The legal basis is your consent (Art. 6(1)(a) GDPR and § 25(1) of the German TDDDG for access to the device). As the app is aimed at children, consent is given by a parent (Art. 8 GDPR). The decision, its time and the version of the consent text are stored locally on the device only.
Withdrawal: you can withdraw your consent at any time with effect for the future under Settings (gear icon) → Game → "Privacy (for parents)". Turning off requires no check; transmission stops immediately. The lawfulness of processing before the withdrawal remains unaffected (Art. 7(3) GDPR).
Firebase Crashlytics and Firebase Analytics are provided by Google LLC and/or Google Ireland Limited. Data may be transferred to the USA or other third countries as part of this. For the USA, an adequacy decision of the EU Commission exists (EU-US Data Privacy Framework, Art. 45 GDPR); Google LLC is certified under this framework. In addition, Google relies on the EU Standard Contractual Clauses (Art. 46 GDPR). Details: firebase.google.com/support/privacy.
Local game data remains on the device until the app is uninstalled or progress is reset. Exception: the “early user” flag (a thank-you for testers) survives a progress reset and is only deleted when the app is uninstalled.
You have the following rights regarding your personal data vis-à-vis the data controller:
Since learning progress is stored exclusively locally on the device, these rights in practice mainly concern the crash/usage data collected via Firebase. You also have the right to lodge a complaint with a data protection supervisory authority (Art. 77 GDPR) — typically the authority in your country or state of residence. For Hesse (Germany), this is the Hessischer Beauftragter für Datenschutz und Informationsfreiheit.
Ixilotl has no user account and does not collect names, email addresses, or any other identifiers that would identify a person. The only data transmitted to Google (crash and usage data via Firebase Crashlytics/Analytics, see above) is linked to a random, pseudonymous device identifier — not to you personally. This means we cannot match a deletion request received by email to a specific person's data (Art. 11 GDPR).
Deletion therefore works directly on the device:
This immediately stops transmission and resets the app's device identifier in Firebase Analytics — severing the link between your device and all previously collected pseudonymous data. Local learning progress is unaffected (it is stored exclusively on the device and never sent to us); it can be removed separately by uninstalling the app.
Crash reports not yet sent are deleted on the device without consent. There is no on-device reset for crash reports already sent; these are subject to automatic deletion after 90 days (see "Retention period" above). For anything beyond this — for example if you can provide additional information to identify your specific data, or for general questions about deletion — contact us at support@ixilotl.de. We handle such requests within 30 days.
Ixilotl is aimed at primary-school-age children. The app does not collect personal data that would allow identification of a child. There is no chat feature, no social networks, and no advertising. The name entered in the game and the learning progress stay on the device only. Usage and crash data are only transmitted if a parent has consented (see "Consent by parents"); consent can be withdrawn at any time in the settings.
The app currently offers no purchases. A full version is planned as a one-time purchase through the Google Play Store. Payment processing and the associated data handling will then be subject to Google's privacy policy; we do not receive any payment data.
The website ixilotl.de is hosted on GitHub Pages (GitHub, Inc., USA, a subsidiary of Microsoft Corporation). When pages are accessed, GitHub processes technically necessary connection data, in particular the IP address, date and time of access, the page requested and browser information, in order to deliver the website and protect it against abuse. The legal basis is our legitimate interest in a secure and functioning website (Art. 6(1)(f) GDPR). GitHub is certified under the EU-US Data Privacy Framework. Details: GitHub privacy statement.
The website sets no cookies, uses no analytics or tracking services and embeds no third-party content. Fonts are loaded directly from ixilotl.de, not from external servers.
For enquiries we offer a contact form. It is not embedded on ixilotl.de but opens on the website of the form service Tally (Tally BV, Ghent, Belgium), which we use as a processor (Art. 28 GDPR). We process the information you enter (email address, message, optionally your name) as well as technically necessary connection data such as your IP address. According to Tally, form data is stored encrypted in Europe; Tally lists its sub-processors at tally.so/help/gdpr.
All our email addresses (…@ixilotl.de, …@sumpfsoftware.de, …@sumpfsoftwarestudio.de) are hosted by our hosting provider INWX GmbH, Prinzessinnenstr. 30, 10969 Berlin, Germany, on servers in Germany. INWX operates the inboxes on our behalf (Art. 28 GDPR) and does not use their contents for its own purposes. The redirect pages of sumpfsoftware.de and sumpfsoftwarestudio.de are covered by the section “This website” (GitHub Pages) accordingly.
If you email us or create a request via the beta page (the form merely opens your own email program; the website itself stores nothing), we process the information in your email: your email address, your name if provided, and your message. For beta requests this may also include – only if you choose to provide them – a different email address for the access link and a phone number for questions. We use these details solely for activation and questions about the beta and do not pass them on to third parties.
The app contains a feedback form. It does not send anything itself: when you tap send, your own email program opens with a pre-filled email to feedback@ixilotl.de. Only if you send that email do we receive:
You can review and change the email before sending it. Before the email program opens, there is a short check for adults (entering a date of birth, which is not stored); children may fill in the form, but only an adult can send it.
Draft stays on the device: a partly completed feedback form is saved locally on the device so that it is still there next time. It is not transmitted, and it is deleted as soon as the email program has opened, when you discard it, when the game progress is reset, or when the app is uninstalled.
For privacy-related questions:
Sebastian Buhl
support@ixilotl.de