"Game Development in Elm: Build Your Own Tooling" by James Gary

From a channel Lumen includes in full: elm-conf's archive is full talks on the Elm language and typed functional front-end design — including Richard Feldman's 'Making Impossible States Impossible' — by Elm core contributors and practitioners.

A 23-minute video from elm-conf's catalogue; the title names its topic.

Video by elm-conf, played through YouTube's embedded player.