Unclear how to overwrite theme CSS files

Hi,

Thanks for the project! I'm trying to use it to make a landing page for my project, except I already made the landing page in HTML/CSS, but would still like to take advantage of the changelog and mdbook features.

This part of the docs has me confused:

> Currently, to create a new theme, you need to follow the directions above in "Customizing Themes" and overwrite the given CSS.

Does this mean I should run `oranda build` and then do `mv public/custom.css public/oranda-v0.6.1.css` (or something else) to overwrite the CSS?

Or is it saying I should surround my custom CSS with `@layer overrides { ... }`? I tried that and the page still includes `oranda-v0.6.1.css` and its directives still override mine (eg, it changes the default body `height`, its body `font-family` overrides mine, etc.)

Thanks for any help!