Tell us what’s happening:

Your code so far

:root {
  --red-color: red;
.red-box {

  background: red;
  height: 200px;
<div class="red-box"></div>

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 6.1; 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:

Welcome, proa.

Please edit your post to include a descriptive title, as well as fill in the Tell us what’s happening section.

If you do not ask a question, we cannot answer.


Your code as shown can not be submitted because you have removed:

background: var(--red-color);

Do not do that! Instead simply add:

background: red;

before it and it works!