Learn CSS Variables by Building a City Skyline - Step 42

Tell us what’s happening:
Describe your issue in detail here.
Okay so I have tried to add bb1-window inside with adding another class and I have tried it with another “

nested inside the original div, and I have tried to add a comma then my bb1-window but it keeps telling me “ You should add the bb1-window class to the .bb1a element” I have put it in everyway I know how and it tells me it’s 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"class="bb1-window"></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%;
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);
}

.bb1-window {
height: 10%;
background: linear-gradient(
    var(--building-color1),
    var(--window-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 (iPhone; CPU iPhone OS 15_6_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.6.1 Mobile/15E148 Safari/604.1

Challenge: Learn CSS Variables by Building a City Skyline - Step 42

Link to the challenge:

I tried to type the way I tried to type it in differently but it doesn’t show on the comments I’m sorry for no further information

Okay I figured it out, tip for anyone who needs it, remember when adding a second class to a element you don’t need two “class” just one for each