I basically didn't understood that how do we add a fallback declaration in front of other declaration?

HTML-CSS
1

Tell us what’s happening:

Your code so far


<style>
:root {
  --red-color: red;
}
.red-box {

  background: var(--red-color);
  height: 200px;
  width:200px;
}
</style>
<div class="red-box"></div>

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.116 Safari/537.36.

Challenge: Improve Compatibility with Browser Fallbacks

Link to the challenge:

2

there is an empty line to show where to add the non-variable-using background rule