This is a Minecraft clone that is still in progress that will run in your browser.
You can run it here on GitHub pages or you can clone this repository and run it locally from index.js
It includes Multiplayer, using WebRTC, and Firebase for Signalling.
Starting a server will open a tab that is the actual server which will host the world and handle all the physics and world updates, while the client tab will be the one you play on. There is no cloud server, so the machine that starts the server will be the one hosting the world and handling all the physics and world updates.