You can use
partials or you can specify
custom_css in your configuration :
[reveal_hugo] custom_css = "css/custom.css"
custom.css can be present in
partials or with
custom_js in your configuration:
[reveal_hugo] custom_js = "js/custom.js"
custom.js can be present in
Here the slide has an additional css class
slide shortcode. This class is hosted in a custom CSS.