Several years ago, Elm used to have this powerful yet confusing concept called “signals”. Pragmatic Studios had a dedicated course on the topic by the same presenter (Mike Clark).
The course was a real light-bulb moment for me 
and a concept that had previously been really confusing made so much sense. It was well presented, had lots of helpful visualizations, and had source code examples I could download and modify.
Note that since then, Elm has been streamlined and signals were removed so that course isn’t really relevant anymore.
TL;DR I haven’t taken this course specifically but I was extremely satisfied with a different Pragmatic Studios Elm course I took by the same presenter several years ago 
