Learn CSS Variables by Building a City Skyline - Step 22

Tell us what’s happening:
Describe your issue in detail here.

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;
}

.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);
}

.bb2 {
  width: 10%;
  height: 50%;
}
--building-color2{
  background-color: #66cc99;
}
.bb3 {
  width: 10%;
  height: 55%;
}

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

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/106.0.0.0 Safari/537.36

Challenge: Learn CSS Variables by Building a City Skyline - Step 22

Link to the challenge:

Add a new background color (as a variable) below the existing one in your code. It should look like this:
image

If you look at e.g. the selector .bb1c in your CSS code, you see the means of how to add a new background- color:
image