You can play around in the guestbook. I'm in it right now and you can see me editing things.

Cloudflare Durable Objects are pretty cheap and I'm using it like a very basic pub/sub with each deck having it's own DO. I did some calculations and it should be well within my spend limits.

Something super small that I've noticed in the guestbook: since there're a lot of people connected, I noticed that every time I received an update, I lost the focus of my text element, so it was a little bit difficult to write something.

It may be annoying if two users are working at the same time in the same project.

Again, very cool project! :)