> If I have to edit CSS, which files do I have to edit and why?
Seems to be the wrong approach. Framework code shall never be changed. The challenge is to design e.g. your own button that is based on the Bootstrap button. This approach is upward-compatible.
Assuming this is indeed the case, I'm surprised this isn't a big attention-getter on the bootstrap site. I also have no idea how I'd go about 'extending' the bootstrap button into something for me.
Seems to be the wrong approach. Framework code shall never be changed. The challenge is to design e.g. your own button that is based on the Bootstrap button. This approach is upward-compatible.