Live with greater awareness and intention
iPhone users: Please use the browser tab only rather than "Add to Home Screen". As iPhone keeps installed home-screen apps in a separate, disconnected storage, so your access won't carry over and you'll get locked out.
Android users: Pick one way to use the app - your regular browser tab, or the installed apk (below) - and stick with that for the whole test. Switching between them partway through will result in you losing your data, lock you out and will interfere with testing results, so please choose once and continue the same way.
For apk downloads outside of the Play Store, you will be asked to allow installs from your browser the first time - that's normal.