I totally didn't realize it was collaborative. I thought I was only building rooms for myself lol. Several years ago XKCD released a comic that was different

I totally didn't realize it was collaborative. I thought I was only building rooms for myself lol. Several years ago XKCD released a comic that was different depending the browser, operating system, ip, and referrer you use to view it. I know people uncovered hundreds of versions of it but I never heard a detailed write up about how it worked or how many comics there were available. Does anyone know if they ever figured it out?