DanMage is a project that brings NicoNico-style danmaku (or scrolling chat) to various video sites as a Chrome extension, now supporting YouTube, Twitch and Crunchyroll. It's also deployed as a website, which provides minimum backend support to the Chrome extension, such as storing posted chats and player settings.
To build Chrome extension, run npm run bext which generates an extension.zip, which can be downloaded and unzipped to be loaded by Chrome. It talks directly to the PROD web server.
To run the web server locally, run npm run local which starts at port 8080.
It's deployed to Google Cloud Platform (GCP) by using Google Cloud Build which requires cloudbuild.yaml and Dockerfile.