Privacy Policy
2026-10-13
This policy explains how the operator of Killer Sudoku AI Coach ("the app") handles your information.
1. Information we collect and how we use it
Device ID
When you first open the app, it creates a random ID for your device. It is not linked to your name or phone number. We use it to manage your daily AI coach questions, rankings, feedback, and linking to an account.
Rankings
When you clear a puzzle, the app sends the record of the clear (the puzzle, time taken, number of hints, score, and the order and timing of your entries) to our server and shows it on the world ranking. If you have not entered a nickname, a short ID derived from your device ID (for example, k7m2qa) is used as your name. If you enter a nickname, country or region, the app sends those too (choosing a country/region also enters you in the national and regional rankings). We use this to show rankings and to detect invalid records. Your nickname (or short ID), short ID, country/region and score are shown to other players.
Location (optional)
Only when you choose "set from current location" for your ranking country/region, the app uses your approximate location. Converting it into a country/region is done by your device's operating system, and your location itself is not sent to our server.
Questions to the AI coach
When you ask the AI coach a question, the question and the content of the hint on screen (the explanation of the solving steps) are sent to our AI provider (Anthropic, PBC) to generate an answer. Our server does not store your questions except to count how many you have used. Your conversation history is stored on your device (and in your backup if you create an account).
Feedback
When you send feedback from the settings, we store its content together with part of your device ID, your OS, app version and language, and deliver it to the operator by email. There is no reply function.
Error and crash reports
When an error or crash happens in the app, it sends the error details (message and stack trace), app version, OS name and version, device language and your device ID to our server so we can find and fix the problem. Reports do not include your board, email address or the text of your questions. If something like an email address or ID slips into a report, our server removes it before recording. Reports are stored in Amazon Web Services (CloudWatch) and the operator is notified.
Anonymous usage data (you can turn this off in Settings)
To improve the app (to learn whether people keep playing, which screens and features are used, and where people stop), the app sends anonymous usage events to our server. These are fixed items only: opening and closing the app (days since install, time spent), screens opened, starting, clearing or leaving a puzzle (difficulty, whether it is the daily puzzle, a rough time range, number of hints and mistakes, roughly how much was filled in), whether hints, ads and the AI coach were used (counts and result types only), and changes to the language or settings, together with the app version, OS name and version, display language and the region of your device's language setting (for example, JP). We do not send your board, the text of your questions, your email address or your advertising ID. Your device ID is turned into a one-way value on our server before it is recorded, and it is not linked to rankings or accounts. Records are stored in Amazon Web Services (CloudWatch), and the operator only looks at aggregated numbers (such as the number of users and retention). We do not use third-party analytics services. If you turn off "Share anonymous usage data" in Settings, events waiting on your device are deleted and nothing more is sent (this is separate from ad consent).
Account (email verification, optional)
The email address you enter to create an account is used only to send a verification code and is not stored on our server (we store only a one-way value derived from it to recognize the same account). Emails are sent using Amazon Web Services. With an account, the app stores your records, settings, AI coach conversations and similar data on our server so you can restore them on another device. You can delete your account at any time from the Me tab; deleting it removes your backup and ranking records from our server. See Delete your account and data for details.
Advertising
The app shows ads provided by Google AdMob. Google may collect and use information such as your advertising ID to deliver and measure ads. See Google's advertising policies for details. In the European Economic Area and similar regions, the app asks for your consent before showing ads. On iPhone, the app asks for permission to track (personalize ads across apps) before showing ads; the app works the same if you decline. You can reset or disable your advertising ID in your device settings.
2. Sharing with third parties
Except where required by law, we do not share your information with third parties for purposes other than those above. Information is sent to the AI provider, Amazon Web Services and Google only as needed for the purposes described.
3. Retention
Weekly and monthly ranking records are deleted after each period ends. Feedback is deleted after 30 days and verification codes after 10 minutes. Error/crash reports, anonymous usage data and access logs are deleted after 90 days. Account backups are kept while you use the account.
If you can't use the app or can't log in, email info@chordup.io and we will delete your data within 30 days. See Delete your account and data for how.
4. Children
The app is not directed at any particular age group. Users under 13 should use it with a parent's or guardian's consent.
5. Changes
If we change this policy, we will post the update on this page.
6. Contact
Please contact us from the app (Me tab → Settings → "Send feedback") or by email at info@chordup.io.