I built the classic game tetris with a vanilla JS frontend and a Rails API backend. The backend stores users and games allowing you to save and load your last game as well as view high scores.
The game is playable live at: https://charlie763.github.io/tetris/frontend/
To install, clone the repository, cd into the /backend directory, and run bundle install. Open index.html in the /frontend directory from your browser to run frontend functionality and start a Rails server, rails s from the /backend directory to save and load games.
This repository is available as open source under the terms of the MIT License.