Responsive spacing classes like sm:margin-top--standard or lg:margin-bottom--large apply top/bottom margins at specific screen sizes and up (sm, md, lg).
Margin sizes include:
- none
- small
- standard (1.5rem)
- large (3rem)

Use the format **[screen]:margin-[top|bottom]--[size]** to control vertical spacing responsively.

```
// Example:
margin-top--large sm:margin-top--standard md:margin-top--none
```