I've been working on an MMORPG with integrated with Pepecoin crypto currency.
It's custom built with Node.JS for the backend and Three.JS for the frontend. It runs in the web browser and can run on mobile and desktop however the mobile UI isn't designed very well yet.
The server uses Express as its webserver. Greenlock for the SSL certificate and Socket.IO to handle web sockets.
The frontend is mainly vanilla JavaScript with Three.JS.
The game is an MMORPG based in Ribberon a fantasy world where Pepe is on a quest to become the strongest hero of the land.

You can play at https://pepesquest.com/