Bootstrap / CSS / Sass
Bootstrap source code is included in the theme and can be edited on the fly without using gulp, node, commands or other technical stuff. Just add your styles, save and the built-in compiler will do the trick. You will find files in folder /css/scss/.
Scrollspy / Onepager
If the page is operated as an onepager, Scrollspy recognizes at which point it is being scrolled and sets an active class to the respective menu item. This menu item can be styled differently and you always know which one is currently part on the page.