Example 2: Show on Small, Hide on `sm` and Up

Resize your browser window. The orange box will be visible on very small screens (default) and disappear on screens `sm` (640px) wide and larger.

I am visible by default (extra small screens), but hidden on 'sm' (640px) screens and up!

Try making your browser window wider than 640px.

This purple box is always visible, for reference.