Privacy notice

What we hold

As a guest: a random guest ID kept in your browser, the decks you study, your answers, when each card comes back and the days you finished a Zap.

With an account: the same progress, your email address and, if you give one, the first name the app greets you with. If you sign in with Google, Google shares your name and email with us; nothing else.

If you challenge a friend: the challenge, each friend's score and, only if you or they type one, a first name shown with it. A challenge and what belongs to it are deleted after 30 days, or with your account.

We count visits and Zaps to improve the app, without your email, name or guest ID in those counts.

If you ask for a deck we don't have: the topic you typed is kept without your name or ID. Your vote for it is linked to your guest ID or account and deleted with it. With an account, you can choose one email when that deck is ready; it has a one-click unsubscribe.

Why

To bring each card back at the right time, keep your streak, let you sign in on any device and answer you when you write to us. Never to sell, and never for ads.

Reminder emails

Signed-in learners get reminder emails by default at 6:00 PM in their time zone, only on days when cards are due and the Zap isn't done yet. You can stop them in one click with your mail app's Unsubscribe, stop or pause them from the links in any email, or change them in Settings. Resend sends them.

Where

Your data is stored by Supabase in the United States; Cloudflare serves the app.

Who processes it for us

Supabase (database and sign-in), Cloudflare (hosting), Resend (sign-in, deck-ready and reminder emails), Google (only when you use Google sign-in) and Sentry (error reports, without your email, name, guest ID or answers).

How long

We keep your progress while you use Brain Zap. Backups keep a copy for up to 7 days, then it is gone.

When you delete your account, your live data goes at once. We keep a deletion record of two random IDs for 8 days, so restoring a backup can't bring your account back, and encrypted backups keep your data for up to 7 days.

No ads, no tracking

No ads, no third-party analytics and no tracking cookies. A guest has no cookie at all; signing in sets one cookie that keeps you signed in.

Children

You must be 16 or older to create an account. Anyone can study as a guest, with no email or name. If you think someone under 16 gave us their email, write to us and we delete their account.

Your choices

You can download your data and delete your account yourself in Settings. Questions? Write to cast3labs@gmail.com; we answer within 3 working days.

Changes

When this notice changes, we update this page and its date, and tell signed-in learners before a change that matters to them applies.