This might be a bit niche, but I created an online version of the four-player Mahjong game. Unlike most online services, this one doesn’t automate anything or check the rules, but it requires “manual” play - drawing an dealing the right tiles, etc. It’s intended to be played together with a voice connection.
It was a small project, but there were many subtle usability problems to solve. I’m especially proud of mouse position sync between players and smooth interpolation. It really contributes to the feeling of “being there”.
About page (and a gameplay video): https://pwmarcz.pl/autotable/about.html
Source code: https://github.com/pwmarcz/autotable
Blog post about developing the game: https://pwmarcz.pl/blog/autotable/