Privacy Policy
The iOS app “キラーナンプレ” (Killer Sudoku, the “App”) and this website are provided by Yuki Sensui, a sole proprietor in Japan (the “Operator”). This policy explains what information the Operator handles, how it is used, how long it is kept, and how you can delete it.
Summary
- The only data that leaves your device is what the Daily Puzzle (“今日の一問”) leaderboard needs, and only if you choose to join it. If you don’t join, nothing is sent.
- The App does not collect your name, email address, phone number, location, contacts, or photos. There is no sign-up; you take part as an anonymous player.
- The App contains no advertising, analytics, or tracking. We never sell your data.
- You can delete your data from the server at any time: in the App’s Settings (“設定”) tab, under “ランキング” (Leaderboard), tap “ランキングをやめる” (Leave the leaderboard).
1. Information we collect
When you join the leaderboard
When you solve the Daily Puzzle, the App asks whether you want to join the leaderboard. If you choose “今はしない” (Not now), it asks again the next time you solve it. You can also join from Settings. Once you join, the App registers anonymously with the server the next time it uses the leaderboard, and the following information is handled.
| Information | When | Purpose |
|---|---|---|
| Anonymous player ID and an authentication token | At registration | To link your results to your device. The token is stored in your device’s keychain; the server keeps only a one-way hash of it. |
| Friend code | At registration (can be regenerated on the leaderboard screen) | To add friends |
| Nickname (optional) | When you enter one | To show on the leaderboard. It is checked automatically for inappropriate content (see below). |
| Friend connections and when they were made | When you enter someone’s friend code, or someone enters yours (either way, you both become friends) | To show the friends leaderboard |
| Daily Puzzle start time | When you open the Daily Puzzle | To verify solve times (fraud prevention) |
| Results (time, number of mistakes, number of hints, whether assist features were used, time submitted) | When you solve the Daily Puzzle | To rank and display results. The completed grid you send is only compared with the solution and is not stored. Results under 30 seconds are stored but not shown. |
| Last active time | When you use the server (updated at most once a day) | To delete players who have been inactive for a long time |
| Rate-limit counters | Each time you use the server | To prevent abuse. Registrations are counted per IP address transformed with a secret key (HMAC); everything else per player ID. |
Other participants can see your rank, nickname (“ななし” if not set), time, mistakes, hints, whether assist features were used, and how many players are listed. Your friends also receive an internal ID (used to remove a friend) and when you became friends. Please do not use your real name or other identifying information as your nickname. You can change your nickname but not clear it; to remove it, leave the leaderboard.
When you contact us
If you email us, we handle your email address, your name (if given), and the content of your message (including any device model or iOS version you include) in order to reply.
When you visit this website
This website runs on a cloud service provider we use, which processes communication data such as your IP address to deliver the pages. The Operator does not keep access logs. No cookies or analytics tools are used.
Information that stays on your device
Your records, saved games, settings, practice stats, and gallery are stored only on your device and are never sent to the Operator. They are removed when you delete the App. However, the leaderboard token is kept in the keychain, so if you reinstall the App on the same device you may continue as the same player.
When you “share” a result or your friend code, it is sent to the app you choose (such as Messages) under that app’s terms.
2. How we use information
We use the information only for the following purposes:
- To provide the Daily Puzzle leaderboards (global and friends)
- To prevent fraudulent results and abuse of the server
- To keep inappropriate nicknames off the leaderboard
- To investigate problems and keep the service running reliably
- To respond to your inquiries
We do not use information for advertising, profiling, or combining it with data from other companies (tracking).
3. Retention and deletion
| Information | Retention |
|---|---|
| Player ID, friend code, nickname, friend connections, results | Until you leave the leaderboard. Automatically deleted 12 months after you were last active. |
| Daily Puzzle start times | Until that day’s submissions close (about 2 days) |
| Rate-limit counters | Automatically deleted by the next hourly job after each hourly window ends |
| Server error logs (error details only; no IP addresses or request contents) | Up to 7 days |
| Temporary copy of the global leaderboard | 60 seconds |
| Database backups (taken automatically by our provider for recovery) | Up to 30 days. Deleted information also disappears from backups after this period. |
| Support emails | 1 year after the inquiry is resolved |
How to delete: In the App’s Settings tab, under “ランキング” (Leaderboard), tap “ランキングをやめる” (Leave the leaderboard). Your player ID, friend code, nickname, friend connections (you are also removed from your friends’ lists), start times, results, and per-player rate-limit counters are deleted from the server immediately, and the token on your device is discarded. Deleted information cannot be restored. If you join again later, you start as a new anonymous player.
Deleting the App alone does not delete server data. If you reinstall the App on the same device, you can delete it as above. If you can’t, please contact us (it is also deleted automatically after 12 months of inactivity).
4. Service providers and international processing
The Operator entrusts the handling of information to the following types of providers. They process information only for the purposes described in this policy. The names of our providers are available on request.
| Type of provider | Service | Country and where data is processed |
|---|---|---|
| Cloud service provider | Leaderboard server, database, temporary cache, error logs, automatic nickname checks (AI), and this website | A U.S. company. The database is stored in a data center in a country the provider selects within the Asia-Pacific region (the specific country is not disclosed). The cache, nickname checks, and traffic may be processed in data centers worldwide. |
| Email service provider | Receiving and storing support emails | A U.S. company. Processed in data centers worldwide. |
Because these providers are located outside Japan, they are “third parties in a foreign country” under Article 28 of Japan’s Act on the Protection of Personal Information (APPI). The Operator has confirmed that these providers maintain systems meeting the standards set by the Personal Information Protection Commission (APPI Art. 28(1)), and takes measures under contract (data processing addenda) to ensure continued appropriate handling. Information about these measures is available on request.
The United States does not have a comprehensive federal privacy law equivalent to the APPI, though state laws and other rules provide protection (Personal Information Protection Commission survey of foreign systems, in Japanese). The rules of the country where the database is stored can be checked in the same survey.
Except where required by law, we do not provide your information to third parties without your consent (other than showing the information in Section 1 to other leaderboard participants).
Automatic nickname checks
When you choose a nickname, it is checked against a list of prohibited words and then sent to an AI service of our provider to decide automatically whether it is suitable to show worldwide. Rejected nicknames are not stored. This check only decides whether a nickname can be used; it does not produce legal or similarly significant effects on you.
5. Security measures
- Organizational: The Operator is personally responsible for handling personal information, keeps an inventory of what is handled, where, and for how long, and reviews it whenever features change.
- Personnel: Only the Operator handles the information; no one else is given access.
- Physical: Devices used for administration are protected with screen locks and storage encryption.
- Technical:
- All communication between the App, the server, and this website is encrypted with HTTPS.
- The server stores only a hash of your authentication token. On your device, the token is kept in a keychain item that stays on that device only (it is not moved to other devices through backups).
- IP addresses are stored only as values transformed with a secret key, and are deleted after each window ends.
- Only the Operator holds the accounts that administer the server and database, protected by two-factor authentication.
- We handle only the information the leaderboard needs.
6. Requests for disclosure, correction, deletion, etc.
You may request notification of the purposes of use, disclosure (including in electronic form), correction, addition, deletion, suspension of use, erasure, or suspension of third-party provision of your information held by the Operator.
- You can delete your data immediately in the App with “ランキングをやめる” (Leave the leaderboard).
- You can change your nickname at any time from the leaderboard screen.
- For other requests, please email us at the address below. Because we hold only an anonymous player ID, we will ask for the friend code and nickname shown in the App to confirm your identity. We will normally reply by email within two weeks. There is no fee.
7. For residents of the EU, UK, and similar jurisdictions (GDPR)
The App is currently not distributed in the EU, the European Economic Area, the UK, or Switzerland. If we nevertheless handle information of residents of these regions, we do so as follows under the EU General Data Protection Regulation (GDPR), the UK GDPR, and similar laws. The controller is the Operator (Yuki Sensui).
Legal bases
- The leaderboard (player ID, friend code, nickname, friend connections, start times, results, last active time): your consent (GDPR Art. 6(1)(a)). You can withdraw consent at any time with “Leave the leaderboard.” Withdrawal does not affect the lawfulness of processing before it.
- Preventing fraud and abuse, automatic nickname checks, and error logs: our legitimate interest in running a safe and fair leaderboard (GDPR Art. 6(1)(f))
- Replying to inquiries: our legitimate interest in responding to your request (GDPR Art. 6(1)(f))
Joining the leaderboard is optional. If you don’t join, every feature other than the leaderboard still works.
Recipients
Other leaderboard participants (the information in Section 1), and the processors in Section 4 (cloud service and email service providers).
Your rights
You have the rights of access, rectification, erasure, restriction of processing, and data portability. See Section 6 for how to exercise them. You may also lodge a complaint with the supervisory authority in your country.
Right to object: You may object at any time to processing based on legitimate interests (the second and third items above). Please contact us.
International transfers
Your information is processed by the Operator in Japan and by our providers in the United States. Japan is covered by adequacy decisions of the EU and the UK. Transfers to our providers rely on the EU–U.S. Data Privacy Framework (and its UK Extension) and the Standard Contractual Clauses in their data processing agreements. Copies and details are available from us on request.
8. Children
The App is not directed at children and has no age verification. If you are under 13, please join the leaderboard only with a parent’s or guardian’s consent. If a parent or guardian learns that a child’s information was sent without consent, please contact us and we will delete it promptly.
9. Changes to this policy
We may update this policy when the App’s features or the law change. For significant changes, we will post a notice at the top of this page and in the App’s release notes on the App Store. Before changing the purposes of use, we will give notice and, where required, ask for your consent again. The latest version is always available here.
10. Contact
Operator: Yuki Sensui (sole proprietor, Japan)
Email: support@g4rds.dev