Some months ago I made this Morse Code Universe where people travel through zones, stumble upon each other, and communicate in morse code.
All they can do is use morse code to communicate, even the names are assigned automatically. There is a zone map with hundreds of zones, zones with recent activity get a red hue. Secret zones can be unlocked if you happen to use one of the sekrit morse code words.
It's a casual mmorpg/townsquare that is fundamentally safe since the best you can do is focus to type a very offensive word in 20 seconds.
I stumbled upon some random people who visited the site as I was developing it. Taught some the words to enter the secret zones as a game, took them on a tour. Also met a morse code aficionado and we had a little conversation in morse code, eventually met him in another site I have.