[yoz-y]

Using cookies is brittle because they can get purged. They also don't sync. You could display some base64 encoded data to copy and paste between sessions but that would be quite unpleasant.

One way would be to auto-generate accounts and display some random identifier to keep. Or maybe just offer e-mail to which they would send you a login link... There are other options but login with OAuth is not the worst.

[sli]

So use the browser's local storage feature and realize it's just a little toy and not so important that it needs bulletproof data retention.