Hey, I'm the developer behind Grapevine, thanks for the mention! If anyone is interested in how the Grapevine web client works, it's all open source and written in Elixir with the front end being React/Redux.

The main application: https://github.com/oestrich/grapevine

And the telnet connection pool node: https://github.com/oestrich/grapevine-telnet

Few months back, there was a story here at HN about someone writing just such game to be played over a SSH connection. There were huge problems with the fact that you cannot reliably detect when the user stops pressing a key.

IIRC, it was an action/arcade game, though, so it might be more tolerable for something not twitch-based.