---
id: 612e95ef2e4bdf41f69067f9
title: ステップ 12
challengeType: 0
dashedName: step-12
---

# --description--

`#piano` の `margin` の値を `80px auto` に設定してください。

# --hints--

`#piano` セレクターには値が `80px auto` に設定されている `margin` プロパティが必要です。

```js
assert(new __helpers.CSSHelp(document).getStyle('#piano')?.margin === '80px auto');
```

# --seed--

## --seed-contents--

```html
<!DOCTYPE html>
<html lang="en">
  <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>
```

```css
html {
  box-sizing: border-box;
}

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

--fcc-editable-region--
#piano {
  background-color: #00471b;
  width: 992px;
  height: 290px;
}
--fcc-editable-region--
```
