Stewart Butterfield developed a 2d massively multi player game called "Game Neverending":

https://gamicus.fandom.com/wiki/Game_Neverending

It let users create and upload content like text and pictures, so it had a nice image uploader component and content management system.

That didn't work out, so they took the image uploader and cms and pivoted to making an app called "Flickr", which Yahoo bought.

Later on he redeveloped a new version of GNE in Flash called "Glitch", that was a whole lot like Habitat, in that it had these long horizontal areas you could walk left and right around, and chat with other people with avatars, and do fun stuff.

https://en.wikipedia.org/wiki/Glitch_(video_game)

That didn't work out either, so he took the rooms based chat messaging back-end, and pivoted to an app named "Slack".