Give your xaringan slides some style with xaringanthemer within your slides.Rmd file without (much) CSS.

First, add the xaringan-themer.css file to the YAML header of your xaringan slides.
Then, in a hidden chunk just after the knitr setup chunk, load xaringanthemer and try one of the theme functions.
```{r xaringan-themer, include = FALSE}
library(xaringanthemer)
mono_light(
base_color = "#1c5253",
header_font_google = google_font("Josefin Sans"),
text_font_google = google_font("Montserrat", "300", "300i"),
code_font_google = google_font("Droid Mono")
)
```
xaringanthemer is Tab friendly – use autocomplete to explore the template variables that you can adjust in each of the themes!
