Privacy Policy

Who this covers

Lumio Data Labs publishes the Mahjong Sensei iOS app and this website, including the mahjong game you can play in the browser. This policy covers both. You can reach us at support@lumiodatalabs.com about anything on this page.

There is no account to create anywhere in either product. We never ask for your name, your email address, or your phone number, and there is no field in which to type one.

The short version

• We do not sell or share your personal information, and we do not use it for advertising.
• We do not track you across other apps or websites. There is no advertising identifier and no tracking prompt.
• Camera images in the iOS app are read on your device and are never uploaded.
• Two things do reach a network: buying Sensei Pro, and choosing to contribute your finished games in the browser, which is off unless you switch it on.

The browser game on this site

By default, nothing about your play leaves your browser. The game, the rules engine and the AI opponents all run locally on this page.

What is stored on your device

• Your match in progress, in your browser's local database, so you can close the tab and resume later. Starting a new match overwrites it.
• Three small settings values, in local storage: whether you switched on game contribution, the random identifier that goes with it (only once you switch it on), and whether you have dismissed the "get the app" prompt.
• No cookies. We set none at all, and the one request that can leave the page is made with cookies explicitly omitted.

Clearing your browser's site data for this domain removes all of it. Nothing above is sent to us.

What our host sees

The site is hosted by Vercel. As with any web host, Vercel's servers receive your IP address and ordinary request information (which page, which browser, when) in order to send you the page, and retain them briefly in operational logs. We do not use those logs to build a profile of you, and we do not combine them with anything else on this page.

The site loads nothing from anyone else. The typeface, the images, the AI model and the game engine are all served from this domain, so no third party learns that you visited. The site also sends a header that blocks the browser game from using your camera, your microphone or your location.

Contributing your finished games (off unless you switch it on)

Mahjong Sensei's opponents are trained on real games. You can help by contributing yours. It is off by default; the switch is on the contribute page, and it applies only from your next match onwards.

What is in a contribution

When it is switched on, a completed match is sent to us containing:

• the game itself — the tiles dealt, and every move made by every player, including yours;
• what the AI calculated on each of its turns;
• a random identifier, created on your device when you switched the setting on;
• your browser's user-agent string — the line describing your browser and operating system version that your browser sends with every request it makes;
• your language setting, the AI version you played against, and the time the match finished.

We describe this as pseudonymous rather than anonymous, on purpose. There is no name, email or account attached to it, and the identifier is random rather than derived from you or your hardware. But because that identifier is the same across your contributions, and because the user-agent string describes your setup, a contribution is not truly anonymous, and privacy law treats it as personal data. We would rather say so than round it down.

What is never in one

• Nothing from a camera. That is the iOS app, and it never leaves the phone there either.
• Nothing from an unfinished match, and nothing at all before you switch the setting on.
• No name, email or account, because none exists.

Where it goes, and for how long

Contributions are stored privately in our storage at Vercel. They are not publicly accessible; reading them requires our credentials. We use them to train and evaluate the AI that plays against you, and we do not sell them or pass them to anyone else.

A contribution waiting on your device to be sent is deleted automatically after seven days if it cannot be delivered. Contributions we have received are kept as training data until you ask us to delete them.

Turning it off, and deleting what you already sent

Switching the setting off stops any further contributions, clears anything still queued on your device, and deletes the random identifier from your browser.

To have games you already sent deleted, email support@lumiodatalabs.com with your identifier and we will remove them. Copy the identifier from the contribute page before you switch the setting off — switching off erases your only copy, and without it we cannot tell which games were yours.

Usage counters (not currently enabled)

The site is built to support a simple counter for events like "a match was started" or "a hand finished". If we ever enable it, each event would carry only the name of the event, a coarse description of your screen size, and your language — no identifier, no user-agent string, no timestamp, and nothing about your hand or how you played.

It is not enabled today, and it is separate from the contribution switch above. We will update this page before turning it on.

The Mahjong Sensei iOS app

Your camera

The app asks for camera access to read the tiles in front of you. As the permission prompt says:"Mahjong Sensei reads your tiles on-device. Images are processed live and never leave your device." Frames are analysed by a model running on your iPhone and discarded. They are not uploaded, and the app never writes to or reads your photo library.

Your table

Live coaching keeps a spatial map of the table you are playing on, so the guidance stays lined up with the real tiles if you put the phone down and pick it up again. It is stored on your device only. We mention it so that "no images are stored" is not misread as "nothing about your surroundings is stored".

Your games and settings

Match history, tracker state and preferences are kept in the app's own storage on your device and are removed when you delete the app. Like other app data, they are included in your own iPhone backup if you use iCloud or a computer to back up — that backup is yours and Apple's, not ours.

What the app does not do

There is no analytics SDK, no advertising SDK, no advertising identifier and no App Tracking Transparency prompt, because there is nothing to ask about: the app does not track you across apps or websites, and there are no ads.

Purchases

Sensei Pro is sold by Apple. Payment is handled entirely by Apple and we never receive your card details, your billing address or your Apple Account credentials.

To know whether your purchase is active, the app uses RevenueCat, a purchase-management service. RevenueCat receives your purchase and subscription history against an anonymous identifier it generates on first launch; because there are no accounts, no name or email is attached to it. This connection is made when the app starts, not only when you buy something. The design of our purchase screen is also fetched from RevenueCat when it is shown. See RevenueCat's privacy policy.

In Apple's privacy labels we declare purchase history as linked to that anonymous identifier. That is the more cautious of the two defensible answers, and we prefer it.

Diagnostics, in beta builds only

TestFlight and development builds include a diagnostics screen for reporting problems. It does not exist in the App Store version.

You choose which parts to include, and the app cannot send it — it has no way to upload anything. Tapping the mail button opens your own mail app with the file attached, and nothing reaches us unless you press send yourself. The file contains recent practice games and what the coaching model decided. If you include the optional "device and build" section, it also contains the app version, your iOS version, your device model, your language, and a random identifier created once on that install so that two reports from the same tester can be matched. It contains no photos, no contacts, no location, and no name or email.

Diagnostics you email us are kept only as long as we need them to investigate, and in any case no longer than 12 months.

Who else is involved

We keep the list of third parties as short as we can. Each of the following receives only what is described above, uses it only to provide its service to us, and is bound by its agreement with us to protect it to at least the standard set out in this policy.

• Apple — distributes the app and processes all payments.
• RevenueCat — tells the app whether a purchase is active.
• Vercel — hosts this website and stores contributed games.

None of them is an advertising or analytics network, and we share nothing with anyone for advertising.

Children

Mahjong Sensei is not directed at children under 13, and we do not knowingly collect anything from them. If you believe a child has contributed games, email us and we will delete them.

Your rights

Depending on where you live, you have rights over personal information we hold — in Canada under PIPEDA, in the UK and European Economic Area under the UK and EU GDPR, and in California under the CCPA and CPRA. These generally include the right to know what we hold, to get a copy, to have it corrected or deleted, to object to or restrict how we use it, and to withdraw consent at any time.

In practice, the only personal information we are likely to hold about you is contributed games and anything you have emailed us. Write to support@lumiodatalabs.com and we will act on it. For contributed games, include your identifier — it is the only way we can find them. We do not charge for this and we will not ask you to create an account to do it.

We do not sell personal information and we do not share it for cross-context behavioural advertising, as those terms are used in California law.

Changes

If we change this policy we will change the date at the top of the page, and if the change is material — anything that would newly send data somewhere — we will say so on the page rather than quietly amend it.

Contact

Lumio Data Labs · support@lumiodatalabs.com