The first third is a pretty standard introduction: minimize number of files, yadda yadda. The second third talks about how JS/CSS dependency resolution is hand

The first third is a pretty standard introduction: minimize number of files, yadda yadda. The second third talks about how JS/CSS dependency resolution is handled using metadata included in the files themselves. Then it explains a client-side library used for enabling dependency behavior on the frontend, including dynamic loading of files as-needed.