Privacy

The short version

There is no analytics on this site. No Google Analytics, no Plausible, no Meta pixel, no session recording, no heatmaps, and no advertising of any kind. Nothing here sets a cookie to follow you, because nothing here is interested in where else you go.

That is not a promise about intentions, it is a description of the code, and you can check it: open your browser’s network tab and watch what this page requests. The only third parties that ever see anything about you are the three named below, and each of them is there because some specific feature could not exist without it.

If you never make an account

Then nothing about you reaches us at all. The 19 open exercises, every guide and every teaching page work with no account, and your progress through them is written to your own browser’s local storage. It never leaves the machine. We cannot see it, cannot restore it, and are not told it exists.

That also means clearing your site data deletes it, and that it does not follow you to another browser. If that matters to you, an account is what fixes it; if it does not, you never have to make one.

Our server still receives what any web server receives when you ask it for a page: your IP address, the page you asked for, and your browser’s user agent string. That is how the request reaches you.

If you do make an account

Then we hold these, and nothing else:

• Your email address, and your name if your sign-in method gave us one.
• Which of the 84 exercises you have finished, when you finished each one, how many attempts it took, how many hints you used, and how long you spent.
• The days you were active, which is what the streak is counted from.
• Two preferences: whether sound is on, and which exercise you were last on so the site can offer to resume.

Half-finished spreadsheets are not in that list on purpose. A draft you have typed into a grid and not submitted stays in your browser and is never sent anywhere, because it is large, it is specific to the machine you are sitting at, and nobody has ever wanted to resume one somewhere else.

The legal basis for holding this is that we cannot provide the thing you signed up for without it: an account whose progress is not stored is not an account.

If you pay

We never see your card. Payment happens on Polar’s own checkout, so your card number, its expiry and your billing address go to Polar and never pass through this site. The safest way to hold a card number is to never have it.

What comes back to us is the minimum needed to unlock the course: an identifier for your Polar customer record, an identifier for the subscription if you have one, and the date your access runs until. No amount, no card details, no address.

Who else sees it

Three companies, each for one job. None of them is paid to receive your data and none of them is allowed to use it for anything but the job.

Nothing is sold, and nothing is shared with anybody else. If a fourth company is ever added, it appears on this page before it ships.

Certificates are public on purpose

A certificate is only worth anything if somebody else can check it, so a certificate page is readable by anyone holding its link. It shows the name you chose to print on it, the date, and how many exercises were finished. It does not show your email address or link to your account.

You choose that name when you ask for the certificate, and it does not have to be the name on your account. If you would rather it did not exist, ask and it will be deleted.

How long it is kept

For as long as you have an account. Progress is the thing an account is for, so it is not deleted on a timer: somebody coming back after two years should find their work.

Delete your account and the progress, preferences and certificate go with it. Records of payments are kept for as long as tax law requires, which is the one thing we cannot delete on request.

What you can ask for

Under the GDPR you can ask for a copy of what we hold, ask for it to be corrected, ask for it to be deleted, and object to us holding it. None of these requests needs a reason and none of them costs anything.

Most of it you can do yourself without asking: your progress page has a reset, and deleting your account removes the rest. For anything else, write to the address in the notice at the top of this page.

If you think we have handled your data badly and we have not put it right, you can complain to your country's data protection authority.