Has anyone found any documentation of CSS elements and classes used by Freshdesk?

I'm struggling with making even the most basic changes -- not because I suck at CSS, but because I can't find any documentation of which classes and named elements are defined in Freshdesk.

Example: Changing the default appearance of <pre> tags in knowledge base (solution) articles.  I ended up having to go through the HTML source of the page in order to find out that the class name is "article-body", and then I could do:

.article-body {
  pre {
    background-color:rgb(239,239,239);
    line-height:1.3;
    padding:12px;
    border-width:thin;
    border-style:solid;
  }
}

..which worked great -- but what a pain to get to that point! 

Is there *any* documentation that shows how to modify the CSS for things like the page header, menu bar, sidebar, forum posts, etc. -- or do we have to reverse-engineer each page to figure out how to do that? 

Or am I just missing something stupid-simple about this whole process?

Thanks!