Mobile First Styling
I first came across this way of thinking about styles from Adam Wathan. Style for the mobile layout first, and
extend your styles to accomodate for the larger breakpoints. the arguement is that it’s easier to expand a small design into a bigger layout than it is to do the opposite, extending desktop first styles to accomodate for mobile & other smaller screens.
Extending of those styles is then done using
min-width breakpoints. Illustrated much better than I can explain in this video (he uses tailwind in this example, but the principles & mindset apply to vanilla css.) :