Light/Dark theme-awareness for userchrome.css?

Operating system

macOS

Joplin version

3.5.12

What issue do you have?

In my efforts to refine my userchrome/userstyle .css files I'd like to have a single pair that can handle both light and dark modes. Is there a way to set up these files to have variable assignments based on light theme or dark theme setting?
Currently I have one pair for when the light theme is selected, and another pair for when dark is selected.
thanks in advance.