An iPhone only shows a preview of this file, it cannot run it: Apple does not let any browser open a file stored on the phone. Open the address below in Safari or Chrome, then tap Share, then Add to Home Screen. Kvitt becomes an icon like an app, works offline, and your figures stay on your phone.
https://kvitt-r7q2xw.pages.dev/
On a computer or an Android phone, open this file in your browser (Chrome, Edge, Firefox or Safari).