The short version: your order never leaves your browser.
Nothing, server-side. Your order, daily target, energy-unit choice and country preference are kept in your browser's local storage and in the URL of any link you copy. There are no accounts and no databases of visitor data.
We use Google Analytics to count visits and see which pages get used. It sets cookies and collects usage data as described in Google's privacy policy. If you block analytics cookies, the site works exactly the same.
This is a small independent project. If something here worries you, the safest assumption is the simplest one: we can't see your order, and we like it that way.