Improve Compatibility with Browser Fallbacks man

Tell us what’s happening:

Your code so far

  :root {
    --red-color: red;
  .red-box {
    background: var(--red-color);
    background: var(--red-color);
    height: 200px;
<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/70.0.3538.110 Safari/537.36.

Link to the challenge:

Repeating the exact same line twice does not change the CSS at all. The point of this exercise is that some browser versions will not understand background: var(--red-color);, so you want to provide a fallback that those browsers will understand.