A simple dark theme for GitHub pages with no frills
To use this theme, add the following line to your sites _config.yml file
remote_theme: ThomasBoxall/ghp-simple-dark
Then when you deploy the page to GitHub pages, you will get a simple dark (and vaguely responsive) dark theme.
To make something like this has really poor documentation. All the documentation sources send you off down a rabbit hole of installing Jekyll & Ruby and messing around with Gem Files and Bundlers. Surprisingly, you don't actually need to do that.
The sources listed below were the most useful in getting this to work.
A demonstration of the theme can be found here