Good basic CSS class example?

I'm brand new to CSS, only learning it for the purposes of Joplin as I use it to help me with something in a game. I looked at the wiki but it has examples that for someone with 0 knowledge of CSS are way too complex for me. I was wondering, can someone do this:

Provide an example of a CSS snippet that just changes font-size, font, colour, really anything basic when you apply text inside the class and also show me how they used it in the Joplin markdown editor so I know how to apply it? These two basics things should really get me past my first hurdle so I can start learning CSS to further apply it for my needs.

Sorry if this question has gotten anything wrong or isn't detailed enough, brand new - I'd be glad to elaborate if you ask!

You can do something like the following:

With no CSS:


With CSS (userstyle):



.bigredtext {
  color: #ff0000;
  font-size: 30px;
  font-weight: bold;