Once all the packages are installed `gulp sass` will be automatically invoked, which will build the stylesheets with the latest version of the source code.
To compile the scss:
```
npx gulp copy && npx gulp sass
```
To explore the generated CSS and why it's huge, edit the `gulpfile.js` and change `outputStyle: 'compressed'` to `outputStyle: 'expanded'` for the `sass:civicrm` task.
