https://tailwindcss.com/docs/adding-custom-styles#adding-custom-utilities

@import "tailwindcss";

@theme {
  /* ... */
}

@utility catpc {
    background-color: blue;
}
@utility catmobile {
  background-color: red;
}

This works for every utility class in the framework, which means you can change literally anything at a given breakpoint — even things like letter spacing or cursor styles.

https://tailwindcss.com/docs/responsive-design