@miscbrains @bot @pwm I actually got the idea from a game from the 1990s!

At university, someone made a web java applet called "legend of zelda online" and it was a networked "legend of zelda: a link to the past" where multiple links could walk around in a map and explore and fight. The author then made it so that you could run your own server and link them together through doors. This was all around 1998. I used to play it in Netscape Communicator 4 on HP-UX.