Privacy Policy

Without signing in (visitor mode) — five usage data points:

(1) A randomly generated install identifier (UUID v4), stored on your device. It contains no personal information — just a random string. It is not an account and not an advertising identifier; it is used for usage statistics and, when we grant you the full content, to recognise your access entitlement.

(2) Your IP address. (3) The country code derived from that IP address (for example HK or JP) — we derive nothing more precise and do not use GPS. (4) The time of your last request and a request count.

(5) Your device platform (Android or iOS) and the app version — only to know which platform and version people are on.

In visitor mode your study progress (which concept cards you studied, which problems you answered) stays entirely on your device. We never receive it.

When you sign in — in addition to the five above:

(6) Your email address — only if you sign in with Apple or Google and they provide one. WeChat does not give us an email address and we do not ask for one. Apple may give you its "private relay" address (for example [email protected]), which only Apple can resolve to you.

(7) Your name — only if you sign in with Apple or Google, and only on the first authorisation. Apple and Google send the name once; later sign-ins do not include it.

(8) That account's study progress — which concept cards you studied, which problems you answered, and how many you got right. This is so your progress can continue on a new phone. Your handwritten notes are never uploaded — they stay on your device.

(9) An identifier for the sign-in method you used — for example WeChat's openid, or Apple and Google's user identifier. We use it to recognise that it is the same person. We never store the sign-in credential itself (the access token) — the server uses it once and discards it.

We do not collect: your name (unless you sign in with Apple or Google and authorise it), phone number, address, contacts, photos, GPS location, browsing history, advertising identifier (IDFA), health data, or your handwritten notes.

The five visitor usage data points: two purposes — understanding usage (how many people use the app each day, and from which regions), and recognising your access entitlement when we grant you the full content. Kept for 90 days, then deleted automatically.

Account data (email, name, sign-in identifier) and your study progress: kept until you delete your account. Their only purpose is to let you get your own progress back when you sign in.

We do not use this data for advertising, do not sell it to anyone, do not share it with third parties, and do not use it to track you across apps.

To have it deleted earlier, email [email protected], or delete your account in the app under "Settings → Account → Delete account".

Visitor mode: the problems you answered, the concept cards you studied, your current part and position in the deck, and your display language — all written into a SQLite database inside the app's container. We cannot read them and have never received them.

When signed in: study progress is synced to our server (so it can continue on a new phone), but your handwritten notes still stay on your device — we have never received them.

The course content and figures are also stored as files so you can read them offline.

Social sign-in (Apple, Google, WeChat): the native SDKs of these three apps let you sign in with their accounts. The credentials they give you are handed straight to our server for verification (using Apple's and Google's public signing keys, or WeChat's single-use authorization code). Our app never stores your sign-in credential and never posts anything on your behalf.

Meta (Facebook) SDK — ad measurement only: this SDK lets us know "which ad drove this install" and "did the person actually open the app". It sends events such as app launch, app install, first launch, and completed sign-in. We have turned off advertiser ID collection (no IDFA or Google advertising ID is attached to any event) and limited the events to measurement and optimisation — they are never used to build audiences or to target ads at an individual. The app therefore does not need to ask for App Tracking Transparency permission.

Content server: the only other outbound connection is to our own content server (api-conquercalculus.coretrix-tech.com).

The content server's domain is served by Cloudflare's content delivery network (CDN), so your connection passes through Cloudflare first: it handles connection information (such as your IP address) under its own privacy policy. We cannot see, access, or control that data; the data we collect ourselves is not provided to it or to any other third party.

None. The App does not request access to your camera, microphone, photos, contacts, location, Bluetooth, or health data, and does not use an advertising identifier.

The App is rated 16+ on the App Store, and we have not marked it as "made for kids". In visitor mode we do not collect names, email addresses, phone numbers, or any contact details; the only things recorded are the random install identifier and connection information (IP address, country), used for usage statistics and to recognise whether the full content has been granted — never to identify a person.

If a parent lets a child sign in, the email address and name are provided to us by Apple or Google; we only store them. We do not actively collect any data about children.

Delete the data on your device: uninstall the App. The database lives inside the app's container, so removing the App removes it too.

Delete your account: "Settings → Account → Delete account" in the app, or email [email protected]. Deleting it also removes your email address, name, and study progress from our server.

Sign out: "Settings → Account → Sign out" in the app. Signing out clears the progress on this device (so the next person to sign in cannot see your records); the data on our server is kept, and you get it back when you sign in again.

Delete the usage records on our server: kept for at most 90 days, then deleted automatically; email [email protected] to have them removed earlier.

If this policy changes, the date at the top of this page changes too; the new version is published here before it takes effect.

CORETRIX TECHNOLOGY LIMITED · Macau · [email protected]