Source code for blog post: https://alpacaaa.net/blog/post/elm-mastermind-game/
Based on create-elm-app.
Install packages with npm install
Run with elm-app start
Webserver listening on http://localhost:3000
A runnable and editable code sample is available at https://runelm.io/c/f2t
There's also a drag and drop version of this game made by wintvelt!