Diabolical Sudoku Privacy Policy
This is the privacy policy for “Diabolical Sudoku: Hard Logic” (Japanese name: 鬼難易度数独; the “App”). The App is provided free of charge by Touzanbou (Kenta Yamamoto) for iPhone and Android. By using the App, you are deemed to have agreed to the handling of information described in this policy.
Information We Collect
No account registration is required. The puzzles you've solved, boards in progress, your clear records, and your settings are stored on your device and are never collected by Touzanbou.
iCloud and Game Center (iPhone)
If you are signed in to iCloud, your explanation ticket balance and your Daily Challenge streak are synced to your own iCloud to keep them consistent across your devices. Touzanbou cannot access this data.
If you are signed in to Game Center, your achievements and leaderboard records (longest streak and total clears) are sent to Apple's Game Center, and Apple's Privacy Policy applies.
Advertising
To keep the App free, it displays ads from Google AdMob (a banner at the bottom of the screen, and video ads you choose to watch). To show ads and measure their performance, AdMob may collect the advertising identifier (IDFA / Advertising ID), IP address, and information about your device and the App.
On iPhone, the App may ask for permission to track for personalized ads. You can use every part of the App without allowing it, and you can change this later under Settings > Privacy & Security > Tracking on your device.
In some regions, the App first asks for your consent regarding ads. You can change your choice at any time under “Ad privacy settings” in the App's settings.
For how Google handles this data, see Google's Privacy Policy (https://policies.google.com/privacy) and how Google uses information from ads (https://policies.google.com/technologies/ads).
Usage Data and Crash Reports
To improve the App's quality, the App uses Google's Firebase Analytics and Firebase Crashlytics. These services anonymously collect how the App is used (for example, screens viewed, app launches, and session information), crash and performance diagnostics (such as stack traces, device model, OS version, and app version), and an app instance identifier.
You can turn this off at any time under “Send usage and crash reports” in the App's settings. For details on how Google handles this data, see the Firebase privacy information (https://firebase.google.com/support/privacy).
In-App Purchases
Payments for in-app purchases, such as explanation tickets or hiding the banner ad, are processed through Apple's App Store or Google Play. Touzanbou never receives your payment information, such as credit card numbers.
Contact Form
Only when you send a message from the App's settings, the message you enter, your email address (optional), and the technical information needed to investigate an issue (such as OS and app versions) are sent to the developer. This happens only when you choose to send, and nothing is collected automatically.
Security
While we strive to protect your information, no method of transmission over the internet or electronic storage is 100% secure, and we cannot guarantee its absolute security.
Links to Other Sites
Ads and other parts of the App may take you to other sites. Those sites are not operated by Touzanbou, so please review their privacy policies.
Children's Privacy
Touzanbou does not knowingly collect personally identifiable information from children under 13. If you are a parent or guardian and believe your child has sent us personal information, please contact us.
Changes to This Privacy Policy
This policy may be updated from time to time. If changes are made, we will notify you by posting them on this page. We recommend that you review this page periodically.
Contact
If you have any questions or suggestions about this Privacy Policy, please reach out through our contact page.
Effective as of May 25, 2026; revised October 28, 2026 (rewritten to match how the App actually works).