Learn CSS Variables by Building a City Skyline - Step 40

Tell us what’s happening:
Describe your issue in detail here.
The hint says You should apply a background to .bb1a but I already did that what else am I doing wrong?

  **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>

  <div class="foreground-buildings">
    <div></div>
    <div></div>
    <div class="fb1"></div>
    <div class="fb2"></div>
    <div></div>
    <div class="fb3"></div>
    <div class="fb4"></div>
    <div class="fb5"></div>
    <div class="fb6"></div>
    <div></div>
    <div></div>
  </div>
</body>
</html>
/* file: styles.css */
:root {
--building-color1: #aa80ff;
--building-color2: #66cc99;
--building-color3: #cc6699;
--building-color4: #538cc6;
--window-color1: black;
}

* {
border: 1px solid black;
box-sizing: border-box;
}

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

.background-buildings, .foreground-buildings {
width: 100%;
height: 100%;
display: flex;
align-items: flex-end;
justify-content: space-evenly;
position: absolute;
top: 0;
}

/* BACKGROUND BUILDINGS - "bb" stands for "background building" */
.bb1 {
width: 10%;
height: 70%;
display: flex;
flex-direction: column;
align-items: center;
}
.bb1a {
width: 70%;
height: 10%;
background-color: var(--building-color1);
 background:linear-gradient (--building-color1,--window-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%;
background-color: var(--building-color2);
}

.bb3 {
width: 10%;
height: 55%;
background-color: var(--building-color3);
}

.bb4 {
width: 11%;
height: 58%;
background-color: var(--building-color4);
}

/* FOREGROUND BUILDINGS - "fb" stands for "foreground building" */
.fb1 {
width: 10%;
height: 60%;
background-color: var(--building-color4);
}

.fb2 {
width: 10%;
height: 40%;
background-color: var(--building-color3);
}

.fb3 {
width: 10%;
height: 35%;
background-color: var(--building-color1);
}

.fb4 {
width: 8%;
height: 45%;
background-color: var(--building-color1);
position: relative;
left: 10%;
}

.fb5 {
width: 10%;
height: 33%;
background-color: var(--building-color2);
position: relative;
right: 10%;
}

.fb6 {
width: 9%;
height: 38%;
background-color: var(--building-color3);
}
  
  **Your browser information:**

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/105.0.0.0 Safari/537.36

Challenge: Learn CSS Variables by Building a City Skyline - Step 40

Link to the challenge:

yes you definitely have a background style here,
only problem is the colors are variables.
In CSS, all variables must be referenced using the var function
var(–something)

So you just need to use var to reference each variable individually.

Awww so var(–color1), var(—color1) lol that hint is very misleading

do you still need help? If yes please post updated code and/or followup question.