Learn CSS Variables by Building a City Skyline - Step 23

HTML-CSS
1

Tell us what’s happening:
Describe your issue in detail here.
Kind of frustrating that it doesn’t tell you how to add a fallback value. After all this is a new concept. How do I give the fallback a value? Any help is appreciated. Thanks!
.bb2 {
width: 10%;
height: 50%;
background-color: var(–building-color2, fallback- green);
}

Your code so far

<!-- file: index.html -->
<!DOCTYPE html>
<html lang="en">    
  <head>
    <meta charset="UTF-8">
    <title>City Skyline</title>
    <link href="styles.css" rel="stylesheet" />   
  </head>

  <body>
    <div class="background-buildings">
      <div></div>
      <div></div>
      <div class="bb1">
        <div class="bb1a"></div>
        <div class="bb1b"></div>
        <div class="bb1c"></div>
        <div class="bb1d"></div>
      </div>
      <div class="bb2"></div>
      <div class="bb3"></div>
      <div></div>
      <div class="bb4"></div>
      <div></div>
      <div></div>
    </div>
  </body>
</html>

/* file: styles.css */
* {
  border: 1px solid black;
  box-sizing: border-box;
}

body {
  height: 100vh;
  margin: 0;
  overflow: hidden;
}

.background-buildings {
  width: 100%;
  height: 100%;
  display: flex;
  align-items: flex-end;
  justify-content: space-evenly;
}

.bb1 {
  width: 10%;
  height: 70%;
  display: flex;
  flex-direction: column;
  align-items: center;
  --building-color1: #aa80ff;
  --building-color2: #66cc99;
}

.bb1a {
  width: 70%;
  height: 10%;
  background-color: var(--building-color1);
}

.bb1b {
  width: 80%;
  height: 10%;
  background-color: var(--building-color1);
}

.bb1c {
  width: 90%;
  height: 10%;
  background-color: var(--building-color1);
}

.bb1d {
  width: 100%;
  height: 70%;
  background-color: var(--building-color1);
}

/* User Editable Region */

.bb2 {
  width: 10%;
  height: 50%;
  background-color: var(--building-color2, fallback-value);
  fallback: green;
}

/* User Editable Region */

.bb3 {
  width: 10%;
  height: 55%;
}

.bb4 {
  width: 11%;
  height: 58%;
}

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Challenge: Learn CSS Variables by Building a City Skyline - Step 23

Link to the challenge:

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2

See the second project - Fallback values were introduced there

3

The instructions do explain how to add a fallback value:

Step 23
That didn’t work. You should add a fallback value to a variable by putting it as the second value of where you use the variable like this: var(--variable-name, fallback-value). The property will use the fallback value when there’s a problem with the variable. Add a fallback value of green to the background-color of .bb2.

Simply replace the words ‘fallback-value’ above with the required value.

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