Your answers are saved in your browser, and also to our server against the mym_player identifier above. The server copy is what lets your progress survive, because some browsers clear locally saved data after a week, which would otherwise wipe an advent calendar halfway through December. We store the contents of the grid, whether you've finished it, and a note of each puzzle you've ever solved, so a solve can be restored after you restart a puzzle. Nothing else.

Clearing your browser's cookies and site data ends this: the identifier is discarded and the progress saved against it is no longer reachable by anyone, including us.

You don't need an account to play. One only exists so your progress can follow you from, say, your phone to your laptop.

If you create one we store your username, your email address and a scrambled version of your password. The scrambling is one way: we can't read your password, and neither could anyone who obtained the file. We also keep the puzzle progress described above, linked to your account rather than to one browser.

If you upload a picture for your account, we keep a small copy of it, cut to a 256 pixel square. Making that copy strips out the hidden details a photo can carry, such as where and when it was taken and on what device. Only you can see it, in your own menu bar: it isn't shown to anyone else. You can replace or remove it on your account page at any time.

An account only becomes active once you confirm your email address using the link we send you. If it isn't confirmed within 24 hours of our last email, the account and your email address are deleted automatically.

If you change your email address, we send a link to the new one and keep using the old one until it's clicked. We also let the old address know about the change, in case it wasn't you.

You can change your username, email address and password, unsubscribe from emails, reset your puzzles, or delete the account entirely from your account page. Resetting clears every saved grid, on all your devices, and keeps the account and its note of the puzzles you've solved, so you can restore those solves later. Deleting removes your username, email address, picture, every saved grid and every solve along with it, and can't be undone.

Updates are an option on your account. If you tick the box when you create it, or turn updates on later from your account page, we use your email address to tell you about the puzzles and the fundraiser. We don't sell it or pass it to anyone else, and every email we send includes a way to unsubscribe. Creating an account never signs you up on its own, and you can change your mind at any time from your account page.

All of our emails, including account confirmations, password resets and messages sent through our contact form, go through Google's Gmail service, which handles your address only to deliver them.

To stop password guessing and spam, we limit how often some things can be done. When you log in, create an account, ask for a password reset or a new confirmation email, change your email address, or send a message through our contact form, we note the time along with a scrambled copy of your IP address and, usually, of the email address or username involved. The scrambling is one way, like your password's: we can't turn it back into the original, only recognise the same one again.

These notes are used for nothing else. They stop counting after 24 hours and are deleted automatically soon after.

Messages sent through the contact form come to our email inbox with the name and email address you gave, so that we can reply.

If you have an account, you can reset your saved progress or delete the account yourself, from your account page. For anything else, such as progress saved without an account or wanting to know what we hold, please get in touch and we'll sort it out.