Note that the theme object has fields with the same names and semantics as the
options in the "theme" section of the config options printed with the command
streamlit config show.
When using the React template, the following CSS variables are also set
automatically.
css
--base
--primary-color
--background-color
--secondary-background-color
--text-color
--font
If you're not familiar with
CSS variables,
the TLDR version is that you can use them like this:
css
.mySelector {
  color: var(--text-color);
}
These variables match the fields defined in the theme object above, and
whether to use CSS variables or the theme object in your component is a matter
of personal preference.
Other frontend details
Because you're hosting your component from a dev server (via npm run start), any changes you make should be automatically reflected in the Streamlit app when you save.
