PiFl Labs Co., Ltd. ("Company", "we", "us") has established and publishes this Privacy Policy under Article 30 of the Korean Personal Information Protection Act to protect your personal data and to handle related concerns promptly and smoothly. It covers Cell by Cell Sudoku ("App"), a mobile app for iPhone, iPad and Android for solving 9×9 sudoku puzzles offline, and applies to the App in preference to our general Privacy Policy.
The App has no sign-up or login and uses no ads, in-app purchases, or analytics or tracking tools (SDKs). Your puzzle progress, game records, My Puzzles and settings are stored only in the App's private storage on your device, and we cannot see them. Until you join the optional Rankings, the App makes no network requests. If you join, it sends only the rankings information in Section 2 to our rankings server.
1. Purpose of Processing
- App functionality: Restoring the puzzle you were solving (entered digits and notes, undo and redo history, selected cell, solve time and hints used), keeping course progress and My Puzzles, working out stars, points, skill rating, streaks and achievements from your finished games, and remembering your settings — all handled only on the device and never sent to us.
- Rankings (optional): If you join the rankings, showing your place on today's puzzle, this week's points ranking, and comparisons in a family or friends room you join with an invite code. This processing provides the feature you asked for (Article 15(1)(4) of the Korean Personal Information Protection Act).
- Customer support: Receiving and answering inquiries you send by email and letting you know the outcome
2. Information We Process
The App does not require sign-up. The information the App stores on your device, the information it sends if you join the rankings, and the information we receive to answer inquiries is as follows.
| Category | Items | Method · Where it lives |
|---|---|---|
| Game records | The puzzle in progress, entered digits and notes (candidates), undo and redo history, selected cell, solve time, hints used, start time, hint area, course progress, and records of finished games (puzzle, difficulty, start and finish time, solve time, number of blanks, hints, entries and mistakes, longest run of right digits, date of the daily puzzle) | Stored only in the App's private storage on the device. Never sent to us, and we cannot see it |
| My Puzzles | The given digits of puzzles you enter yourself and an optional puzzle name (up to 40 characters); up to 100 puzzles | Stored only in the App's private storage on the device. Never sent to us, and we cannot see it |
| App settings | Auto-Clear Related Notes, Show Wrong Digits, Highlight Same Digits, Show Timer, Sound Effects, Haptic Feedback, Background Theme (Paper, Garden, Night), Appearance, whether you joined the rankings, your nickname, the invite code of the room you joined, the rankings' anonymous account ID and refresh token, and the days and weeks sent to the rankings | Stored only in the App's private storage on the device. Never sent to us, and we cannot see it |
| Rankings (optional) | An anonymous account ID (created at random when you first join) and its sign-in token; a nickname (numbers for an adjective and an animal from fixed lists); today's puzzle result (score = solve time plus 30 seconds per hint, stars, hints, difficulty); this week's total points and number of games; the family or friends room you joined (invite code); times set by the server; the IP address and app information (User-Agent) that come with sign-in requests | Sent over an encrypted connection to our rankings server (Google Firebase: Cloud Firestore in the Seoul region, Firebase Authentication) only if you turn the rankings on. No name, email, contact details, location or hardware identifier (such as IMEI or the advertising identifier) is sent; only an anonymous account ID created at random for each installation |
| Email inquiries | Email address, name (optional), message | Collected only when you email our support or privacy address directly |
After you finish a puzzle, Share Result opens your device's share sheet with the app name, level, solve time and hints used. What you choose to share goes only to the app you pick, never to us.
If you join the rankings, other players in the rankings can see your anonymous account ID, nickname, score, stars, hints, difficulty, submission time, and this week's points and number of games. Your name and contact details are never shown. A family or friends room, though, brings together people who know each other through an invite code, so within a room others may know which nickname is yours.
3. Retention Period
- Game records, My Puzzles and app settings (on the device): Kept on the device until you delete the App, and deleted along with it. Whether they are included in a device backup (an iOS backup, or on Android a backup to your Google Account) or a transfer to a new device depends on your device settings and choices; the rankings data on the device (the anonymous account ID and so on), though, is never backed up on Android and is part of the device backup on iOS.
- Rankings information (on our rankings server): Until you turn the rankings off in the App's settings. Turning them off deletes the results, weekly points, room membership and anonymous account you sent, without delay. If you deleted the App without turning them off, you can ask us to delete them as described in Section 10. Google logs the IP addresses of sign-in requests for a few weeks to prevent abuse and then deletes them; a deleted account is also removed from Google's backups within 180 days.
- Email inquiry records: 3 years after the inquiry is resolved
4. Disclosure to Third Parties
We do not provide your personal data to third parties, except with your consent or where required by law (Articles 17 and 18 of the Korean Personal Information Protection Act).
If you join the rankings, your anonymous account ID, nickname, score, stars, hints, difficulty, submission time, and this week's points and number of games are shown to other players in the rankings (Section 2). This is part of the feature you asked for. Your name, contact details, sign-in token and IP address are never shown to other players.
5. Processing Entrustment
To run the rankings and handle email inquiries, we entrust processing as follows. If you do not join the rankings, using the App involves no entrustment of personal data.
| Processor | Entrusted task | Retention |
|---|---|---|
| Google LLC (Google Firebase: Cloud Firestore, Firebase Authentication) | Storing and processing rankings information, and signing in anonymous accounts | Until you turn the rankings off (then deleted without delay; exceptions in Section 3) |
| Google LLC (Google Workspace) | Receiving and storing company email (inquiry emails) | 3 years after the inquiry is resolved |
Entrustment for the tools we use to manage inquiries is covered by section 5 of our general Privacy Policy.
6. International Data Transfers
If you do not join the rankings, using the App involves no transfer of personal data to other countries. Rankings information (Section 2) is stored in a Google Cloud region in Seoul, Korea, but the anonymous accounts the rankings use are signed in by Google LLC in the United States. Because company email is received and stored with Google Workspace, email inquiries are also transferred as follows.
| Recipient | Country | Purpose | Items | When | Retention |
|---|---|---|---|---|---|
| Google LLC (Firebase Authentication) | United States | Signing in the anonymous accounts the rankings use | Anonymous account ID, sign-in token, account creation and last sign-in times, IP address and app information (User-Agent) | When you send a result, load the rankings or a room, or turn the rankings off | Until you turn the rankings off (IP addresses: a few weeks; backups: within 180 days of deletion) |
| Google LLC (Google Workspace) | United States | Receiving and storing company email (inquiry emails) | Email address, name (optional), message | When an email is received | 3 years after the inquiry is resolved |
Contact details and further information for the recipient are set out below.
Transfer details: Google LLC (Google Workspace)
United States · 1600 Amphitheatre Parkway, Mountain View, CA 94043 · privacy contact: Google privacy inquiry form
- Items: email address, name (optional), message.
- When and how: when your inquiry email is delivered to our mailbox (Google Workspace), sent over an encrypted connection.
- Purpose: receiving and storing company email (inquiry emails).
- Retention: 3 years after the inquiry is resolved.
- How to refuse and its effect: if you do not send us an email inquiry, nothing is transferred. You just can't get a reply by email; the App works the same.
Transfer details: Google LLC (Firebase Authentication)
United States · 1600 Amphitheatre Parkway, Mountain View, CA 94043 · privacy contact: Google privacy inquiry form
- Items: anonymous account ID, sign-in token, account creation and last sign-in times, IP address and app information (User-Agent).
- When and how: when you send a result, load the rankings or a room, or turn the rankings off, sent over an encrypted connection.
- Purpose: signing in the anonymous accounts the rankings use.
- Retention: until you turn the rankings off (then deleted without delay). Google logs IP addresses for a few weeks to prevent abuse, and a deleted account is removed from Google's backups within 180 days.
- How to refuse and its effect: if you do not join the rankings, or turn them off in the App's settings, nothing is transferred. You just can't see the rankings; puzzles, courses, records and everything else work the same.
International transfers for the tools we use to manage inquiries are covered by section 10 of our general Privacy Policy.
7. Information Handled by Apple and Google
App Store downloads of the App, crash and diagnostic reports you choose to share with app developers, and TestFlight feedback are handled by Apple under Apple's Privacy Policy. We view anonymous crash reports and TestFlight feedback in App Store Connect only to improve the App.
TestFlight feedback, which includes the tester's email address, applies only to people testing pre-release builds through TestFlight, not to App Store users.
Google Play downloads of the App, crash and ANR (App Not Responding) reports from devices whose users have opted in, in their device settings, to share usage and diagnostics data, and Google Play testing-track participation are handled by Google under Google's Privacy Policy. We view aggregated crash and ANR data in Google Play Console only to improve the App.
Testers on a Google Play testing track are people whose email addresses we add to a tester list in Google Play Console, and they join the test with their Google Account. This applies only to people testing pre-release builds, not to Google Play users.
8. App Permissions
The App requests no device permissions. It does not ask for location, camera, microphone, contacts, photos or notifications access, and it does not show iOS's App Tracking Transparency prompt. The Android app declares the internet permission for the rankings; Android grants it at install without asking, and the App uses the network only if you join the rankings.
9. Data Destruction
- Procedure: Personal data that is no longer needed, for example because its retention period has ended, is destroyed without delay with the approval of the data protection officer.
- Method: Electronic files are permanently deleted so they cannot be recovered. Game records, My Puzzles and app settings are removed from the device when you delete the App. Rankings information is deleted from our rankings server without delay when you turn the rankings off (for Google's IP logs and backups, see Section 3).
10. Your Rights
You (including a legal guardian) may exercise the following rights with us at any time.
- The right to be informed about the processing of your personal data
- The right to decide whether and to what extent to consent to processing
- The right to confirm whether your data is processed and to access it
- The right to request suspension of processing, correction, deletion and destruction
- The right to prompt and fair remedy for damage caused by processing
Exercise these rights by contacting privacy (at) pifl-labs.com; we will act without undue delay. Game records, My Puzzles and app settings stored only on your device are not held by us, so we cannot access or delete them for you; they are erased from the device when you delete the App. Rankings information is deleted at once when you turn the rankings off in the App's settings (for Google's IP logs and backups, see Section 3). If you deleted the App or changed devices without turning them off, email us at the address above with your nickname and the dates you played, and we will find and delete those records.
11. Security Measures
We take the following measures to keep personal data secure.
- A design in which the App sends no information to us unless you join the rankings
- Rankings information sent only over encrypted connections (HTTPS), with server security rules that let each player write and delete only their own records
- Rankings nicknames chosen only from fixed lists, with no free text
- Game records, My Puzzles and app settings kept in the App's private storage on the device
- Access control for inquiry emails
12. Children's Privacy
Unless you join the rankings, the App does not collect personal data from anyone, whatever their age. Even in the rankings it receives no name or contact details; we recommend that children under 14 decide whether to join together with a parent or guardian. If a child under 14 contacts us by email, however, the consent of a legal guardian may be required. If we learn that personal data of a child under 14 was collected without a legal guardian's consent, we will delete it without delay. Parents and guardians may contact us or request deletion at privacy (at) pifl-labs.com.
13. Data Protection Officer
- Company: PiFl Labs Co., Ltd.
- Email: privacy (at) pifl-labs.com
For help using the App, see the support page or email support (at) pifl-labs.com.
14. GDPR (European Economic Area)
If you are located in the EEA, you have additional rights under the General Data Protection Regulation, including the right to access, rectify, erase, restrict processing, data portability, and object to processing. For App Store and Google Play users of the App, the only personal data we process is the information in email inquiries you send us and, if you join the rankings, the rankings information (Section 2; for TestFlight and Google Play testers, see Section 7); game records, My Puzzles and settings are kept on your device and are never sent to us. We process rankings information to provide the feature you asked for (Article 6(1)(b) GDPR). To exercise these rights, contact us at privacy (at) pifl-labs.com.
15. APPI (Japan)
Under Japan's Act on the Protection of Personal Information (APPI), users in Japan have the right to request disclosure, correction and suspension of use of their personal information. For App Store and Google Play users of the App, the only personal data we process is the information in email inquiries you send us and, if you join the rankings, the rankings information (Section 2; for TestFlight and Google Play testers, see Section 7). Contact us at privacy (at) pifl-labs.com.
16. Remedies
To seek remedies for a privacy infringement, you may apply for dispute resolution or consultation to the following Korean authorities.
- Personal Information Dispute Mediation Committee: 1833-6972 (www.kopico.go.kr)
- KISA Privacy Center: 118 (privacy.kisa.or.kr)
- Supreme Prosecutors' Office: 1301 (www.spo.go.kr)
- National Police Agency: 182 (ecrm.cyber.go.kr)
17. Changes to this Policy
This Privacy Policy is effective from October 29, 2026. Compared with the previous version (effective October 19, 2026), it adds the optional rankings (the rankings information in Section 2, the Google Firebase entrustment in Section 5 and the international transfer in Section 6) and the finished-game records and settings kept on the device. Any changes will be announced on this page.