A being is present in exactly one room at a time. If the being is controlled by a user, then the the window for the present room should be displayed for the user. The window of a room should display an icon with the name for each being who is currently present in the room. Each room contains a chat file . Formally, this is a list of text lines, where each line is a contribution to the conversation.
Beings can chat by appending lines to the chat file.
Each line should be tagged with the name of the originator. The most present part of the chat file of a room should be displayed in its window. For each line its originator tag should also be displayed. That means they can sense in which room they are for the moment, which doors there are and where they lead, and which other beings are present in the room for the moment. They can also read and append to the chat file.