Sindome was the first MUD/MOO I ever played. That was 15 years ago. I've been playing it ever since. There are still parts of the world I have yet to explore, NPCs I have yet to interact with, roles that my various characters over the years have not even come close to playing let alone mastering. The game has a rich, 20+ year In Game history. There are tons of resources to help you learn the game, including a YouTube series which introduces the commands. The staff are all volunteers, and a lot of focus is put on training them to handle NPCs consistently and to run plots that keep with the cyberpunk theme. If you haven't checked this game out, you should.