Reminds me of the old ff0000, sadly no longer active, but this is what it looked like: https://www.reddit.com/r/lost_websites/comments/11lao71/ff00...

I had found it on StumbleUpon. We'd log in with friends and just fly around, explore, punch each other, chat with random people across the world on a surprisingly fluid multiplayer setting that was built to promote a web advertising agency (if I remember correctly).

It was really ahead of its time. The old internet was so fun.