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:#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/103.0.0.0 Safari/537.36

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

Link to the challenge:

You should create variable first.
In bb1 selector. Just like previous one, use it as example.

Then you need to assign it.
In your code you always already did stuff like that