Internet Adventure Game Engine (IAGE)
(2022)
I used to be really into text-based adventure games (particularly those made by Infocom back in the day).
I put quite a lot of time in building a game engine that would allow multiple people to play in the same adventure game at the same time (a bit like the old MUDs).
The system was built in Java and used applets to run in a web page (popular in 2001).
I eventually lost interest in the whole thing after getting it to work properly and moved on to the next project.
Thankfully, the people at the IF archive have preserved it for posterity.