Privacy Policy
Jerry Jung ("we") processes personal information of people who use the Star Notebook app ("the app") in accordance with the Personal Information Protection Act of Korea and explains it here.
1. Information kept only on your device
- Items: date of birth (solar or lunar, leap month), birth time or time range, birthplace (city), other people's birth details and nicknames, topic choices, learning progress
- Use: calculating charts and saving your progress
- Not sent: this information is stored only on your device and is never sent to our servers. We cannot see it.
- Deleting it: tap Settings → "Delete all learning data on this device", or uninstall the app. Delete any files you exported separately.
2. Information sent to us (usage data)
We send usage data to improve the app and study its features. Tapping “Next (I agree)” on the first birth-details screen means you agree to sending it as described here. You can turn it off at any time in Settings → "Send usage data to improve the app"; after that nothing more is sent.
- Learning activity: a random installation ID (a value the app generates, not linked to your name or phone number), app version, build type (development or release), language and platform, how birth details were entered (solar, lunar or leap month; whether the birth time is known; the step chosen when it is not; not the date or time itself), whether the topic questions were skipped, screens and lessons used, palaces you choose, check results, unlock outcomes, settings changes, error codes
- Card activity: cards viewed, time-on-card ranges, "Got it / Hard" and reflection answers. Sent separately without the installation ID, so it cannot be linked to a person.
- Today's palace: the palace and hour palace shown, the heavenly stem of the day, your answer (yes, no, or the palace you picked), the time you opened the app (UTC) and your device time zone name, and the engine, method and transformation table versions
- Never sent: the values of your birth date, birth time and birthplace, nicknames, the chart itself, topic choices, location (other than the time zone name), screen recordings
- Under 14: if your birth details show you are under 14, no usage data is sent.
- IP address: when data is sent over the internet, the analytics provider receives your IP address but does not store it (it is set to be discarded on receipt). For learning activity, only your country is estimated from it before it is discarded; for card activity, not even the country is estimated.
3. Purposes
- Finding errors and improving screens and cards
- Usage statistics (which cards are hard, where people stop, and so on)
- Statistics and research using pseudonymized data, such as studying how the palace shown in Today's palace relates to the palaces people choose. Results are used only as statistics that cannot identify anyone.
4. Retention and deletion
- Usage data is kept for 2 years from receipt and then deleted, unless a law requires a different period.
- Electronic files are deleted in a way that cannot be recovered.
5. Sharing with others
- We do not share usage data with others, except where the law allows it or investigators request it through legal procedures.
- If we research pseudonymized data together with an outside party, we will announce it here first and follow the legal procedures.
6. Service providers and international transfers
| Provider | Task | Country |
|---|---|---|
| PostHog Inc. (EU Cloud) | Storing usage data and statistics | Germany (Frankfurt, EU) |
| Google LLC (Google Play) | App distribution | USA |
| Google LLC (AdMob) | Rewarded ads, processing device information such as the advertising ID | USA |
- Information sent to PostHog: the usage data in section 2. It is sent encrypted (HTTPS) over the internet to PostHog's EU servers in Germany while you use the app. It is kept for the period in section 4. Turning off Settings → "Send usage data to improve the app" stops sending and also deletes any records not yet sent from your device.
- AdMob (ads): when you tap "Watch ad", Google receives your advertising ID, IP address, device and app information and ad activity to show the ad and measure it. In places such as the EEA and UK, you can choose in Google's consent form. If you are found to be under 14, personalized ads are not requested. You can avoid ad processing by not watching ads. Retention follows Google's Privacy Policy and data retention practices (policies.google.com/technologies/retention).
- You can reset or delete your advertising ID in your device settings.
7. Your rights
- You can turn off usage data sharing at any time (Settings).
- "Create a new installation ID" switches future records to a new ID. To access, correct, delete or suspend records already sent, contact us by email below. Including your installation ID helps us find them.
8. Safeguards
- The app is built so that birth details never leave your device.
- Usage data is sent over encrypted connections, and access to it is limited.
9. Privacy officer and contact
- Officer: Jerry Jung
- Email: starbust@hanmail.net
10. Remedies
For help with privacy infringements in Korea, you can contact the Personal Information Infringement Report Center (118, privacy.kisa.or.kr) or the Personal Information Dispute Mediation Committee (1833-6972, www.kopico.go.kr).
11. Changes
If this policy changes, we will announce the changes and the effective date in the app.
- Effective date: October 24, 2026