Privacy
Last updated 21 October 2026. Written in plain words.
What is saved in your browser
- A random ID made by your browser, so your daily runs can be told apart from other people's. It is not your name.
- Your history: the days you played and your times, so your streak and stats work.
- Your nickname, if you set one.
What is saved on our server
- Your first daily run each day: the date, your total time, the time each problem took, and your nickname if you gave one. It is stored against your random ID, or your account if you're signed in.
- Usage events, for example "started the daily sprint" or "shared a result", with the page and the browser and device type, so we can see which parts of the site get used.
Practice rounds aren't stored, apart from the usage event saying one started.
The leaderboard is public
Anyone can see the day's leaderboard: the top times and the name next to each. That name is your nickname, or, if you're signed in and leave the nickname empty, your first name from Google. Without either you show as Anonymous.
Signing in
You don't need an account. If you choose to sign in with Google, we also keep your name, email address and profile picture, so your streak follows you to other devices. We never post anything or send you marketing email. If you're under 13, please use the site without signing in.
Who processes it
- Our own server, which stores your daily runs and, if you signed in, your account.
- Our analytics (our own statistics server, and Mixpanel), which receive the usage events. Your name and email go only to Mixpanel's user profile, if you signed in.
- Google, only if you sign in with Google.
We don't sell your data or use it for advertising.
Deleting your data
Clearing this site's data in your browser removes what's kept there. To delete a signed-in account and its runs, email [email protected] from the address you signed in with.
Contact
Questions about this page: [email protected].