I can't understand what is wrong with this

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

  **Your code so far**
/* file: index.html */
<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8" />
  <title>Piano</title>
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <link rel="stylesheet" href="./styles.css">
</head>
<body>
  <div id="piano">
    <div class="keys">
      <div class="key"></div>
      <div class="key black--key"></div>
      <div class="key black--key"></div>
      <div class="key"></div>
      <div class="key black--key"></div>
      <div class="key black--key"></div>
      <div class="key black--key"></div>

      <div class="key"></div>
      <div class="key black--key"></div>
      <div class="key black--key"></div>
      <div class="key"></div>
      <div class="key black--key"></div>
      <div class="key black--key"></div>
      <div class="key black--key"></div>

      <div class="key"></div>
      <div class="key black--key"></div>
      <div class="key black--key"></div>
      <div class="key"></div>
      <div class="key black--key"></div>
      <div class="key black--key"></div>
      <div class="key black--key"></div>
    </div>
  </div>
</body>
</html>
/* file: styles.css */
html {
box-sizing: border-box;
}

*, *::before, *::after {
box-sizing: inherit;
}

#piano {
background-color: #00471b;
width: 992px;
height: 290px;
margin: 80px auto;
padding: 90px 20px 0 20px;
}

.keys {
background-color: #040404;
width: 949px;
height: 180px;
padding-left: 2px;
}

.key {
background-color: #ffffff;
position: relative;
width: 41px;
height: 175px;
margin: 2px;
float: left;
}

.key.black--key::after {
background-color: #1d1e22;
content: "";
}
.key.black--key::after {
left: -18px;
position: absolute;
}
  **Your browser information:**

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.5005.124 Safari/537.36 Edg/102.0.1245.44

Challenge: Step 19

Link to the challenge:

I’ am dumb.It had already the .key.black–key::after