Privacy policy
8 November 2026
This policy covers the game at play.zungjung.org, the Android and desktop apps, and this website. The game is free, non-commercial, and run as a hobby.
Questions and comments: Discord. Discord receives those messages. Corrections and deletion requests: zungjung.mahjong@gmail.com.
Account
Google is the only sign-in. From that sign-in we keep two things: the account id Google assigns to you for this app, and your email address when Google says it is verified. We do not keep your Google name, profile photo, contacts, or anything else from the sign-in token.
The account id and the email are not shown to other players. Signing in again updates the stored email when Google still reports it as verified.
Google runs the sign-in screen under Google's privacy policy. On the web, that screen loads Google's library, which may set Google's own cookies. Our session is kept in the browser's local storage, not in a cookie of ours.
Use of information received from Google APIs follows the Google API Services User Data Policy, including the Limited Use requirements. We use it to run your account and, if you ask, to email you game results. We do not sell it, and we do not use it for advertising.
What you set in the game
- A display name.
- A starting level.
- Notification settings: whether to email results, how often, a language, and a timezone. The timezone only changes the clock printed in those emails. Result email is off until you turn it on.
What other players can see
Other players see your display name, your rating, and the public record of games you played. The leaderboard is visible without signing in. Your email and your Google account are not on it.
Games
Online games, scores, ratings, and challenges are stored on the server so the game and the leaderboard work. Local free play and tutorials stay on your device and are not uploaded.
Recorded games are also used to train and evaluate the game's models. The training copy uses an internal account id and the Elo rating at the time of the game; it does not use your name, email or Google account. If you delete your account, your recorded seats keep the id and the rating but lose the display name, which becomes “not specified”.
On your device
A sign-in session is kept on the device, or in the browser, so you stay signed in. The server stores only a hash of that session token. A session ends when you sign out, after 14 days without use, or 30 days after you signed in, whichever comes first.
On desktop, logs and crash reports stay in the app's data folder on that computer. On Android, the phone's own backup may include the app's local data. That backup is between you and your device account.
Result mail is sent only if you turn it on. Messages come from notify@zungjung.org and each one has an unsubscribe link. They contain game results, with times shown in the timezone you set.
Technical data
The server uses your IP address to limit repeated sign-in attempts and heavy requests. The address is not stored on your account. Ordinary server logs record the time, the address, and the request, so the site can be run and abuse can be handled. Those logs are not used for advertising. The game server is in Germany.
The game does not use an advertising network or a third-party analytics service.
How long, and deletion
The account and its game history stay while the account exists. Email zungjung.mahjong@gmail.com to ask what we hold, to correct it, or to delete the account. The account deletion page gives the steps and the full list of what is removed and what is kept.
Deletion removes the account, the Google link, the stored email, the sessions, the notification settings, and the display name, and takes the name off the leaderboard. A match you played with someone else stays part of their history, no longer attached to a name. The internal account id and the recorded game moves stay for model training and rating integrity, with no link to your person; the public rating history is hidden.
Backups are kept for up to 30 days. A deletion is re-applied automatically after any restore, before the service is made available again, so an older backup cannot bring the account back.
Children
The game is not directed at children under 13, and we do not knowingly keep an account for one. Write to the address above if you think an account belongs to a child under 13. We delete the account if we determine that it does.
Changes
This page is the current policy. The date at the top changes when the text does.