I'm trying to run the google editor demo on my local machine to see if I can use it in my project.
https://google.github.io/closure-library/source/closure/goog/demos/editor/editor.html

I've downloaded the latest stable source code: https://github.com/google/closure-library/releases
Unzipped the source code on my local machine and went to folder closure\goog\demos\editor
And Opened editor.html without changing any source code.
I get an incomplete editor with no buttons and not working as per the demo on github, maybe I'm missing something.

This is a
node.jsproject and not a single HTML page.You should follow the official tutorial to use it.