Improve Compatibility with Browser Fallbacks (Stuck)

Hello guys! I’m stuck here, please

Your code so far

  :root {
    --red-color: red;
  .red-box {
    background: var(--red-color);
    height: 200px;
<div class="red-box"></div>

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 6.2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.100 Safari/537.36.

Link to the challenge:

what do you not understand? what have you tried? what do the failing tests say?

I have tried so many… but thanks anyway.

the correct thing to do is to simply add a RED background just above the first declaration.

background: red;