An attempt to build all web components from the ground up

See, I've been reliant on Bootstrap for a while now. It's great in a sense because it makes it really easy to build mobile-responsive sites fast. But now I think it's time for me to build from scratch because I (think) I have what it takes to do it. Bootstrap is really flexible, but still I want full control over the components of my site. Also, another thing that really bugs me is that all styling is done through classes, because though they're easy to implement, it makes it difficult to say change the navbar throughout because you have to change the classes on each page rather than the .css file. My final objective is to implement this into my own site.