---
id: 5d822fd413a79914d39e9919
title: ステップ 80
challengeType: 0
dashedName: step-80
---

# --description--

左右の境界線のサイズを大きくすると、下端の境界線は左右の境界線の幅を足し合わせた幅にまで広がります。 `.fb1a` の `border-left` プロパティと `border-right` プロパティの値として `2vw solid transparent` を追加してください。 左右の境界線は表示されませんが、下端の境界線の幅が `4vw` になります。

# --hints--

`.fb1a` の `border-left` を `2vw solid transparent` に設定する必要があります。

```js
assert.equal(new __helpers.CSSHelp(document).getStyle(".fb1a")?.borderLeft, "2vw solid transparent");
```

`.fb1a` の `border-right` を `2vw solid transparent` に設定する必要があります。

```js
assert.equal(new __helpers.CSSHelp(document).getStyle(".fb1a")?.borderRight, "2vw solid transparent");
```

# --seed--

## --seed-contents--

```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 building-wrap">
        <div class="bb1a bb1-window"></div>
        <div class="bb1b bb1-window"></div>
        <div class="bb1c bb1-window"></div>
        <div class="bb1d"></div>
      </div>
      <div class="bb2">
        <div class="bb2a"></div>
        <div class="bb2b"></div>
      </div>
      <div class="bb3"></div>
      <div></div>
      <div class="bb4 building-wrap">
        <div class="bb4a"></div>
        <div class="bb4b"></div>
        <div class="bb4c window-wrap">
          <div class="bb4-window"></div>
          <div class="bb4-window"></div>
          <div class="bb4-window"></div>
          <div class="bb4-window"></div>
        </div>
      </div>
      <div></div>
      <div></div>
    </div>

    <div class="foreground-buildings">
      <div></div>
      <div></div>
      <div class="fb1 building-wrap">
        <div class="fb1a"></div>
        <div class="fb1b"></div>
        <div class="fb1c"></div>
      </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>
```

```css
:root {
  --building-color1: #aa80ff;
  --building-color2: #66cc99;
  --building-color3: #cc6699;
  --building-color4: #538cc6;
  --window-color1: black;
  --window-color2: #8cd9b3;
  --window-color3: #d98cb3;
  --window-color4: #8cb3d9;
}

* {
  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;
}

.building-wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.window-wrap {
  display: flex;
  align-items: center;
  justify-content: space-evenly;
}

/* BACKGROUND BUILDINGS - "bb" stands for "background building" */
.bb1 {
  width: 10%;
  height: 70%;
}

.bb1a {
  width: 70%;
}

.bb1b {
  width: 80%;
}

.bb1c {
  width: 90%;
}

.bb1d {
  width: 100%;
  height: 70%;
  background: linear-gradient(
      var(--building-color1) 50%,
      var(--window-color1)
    );
}

.bb1-window {
  height: 10%;
  background: linear-gradient(
      var(--building-color1),
      var(--window-color1)
    );
}

.bb2 {
  width: 10%;
  height: 50%;
}

.bb2a {
  border-bottom: 5vh solid var(--building-color2);
  border-left: 5vw solid transparent;
  border-right: 5vw solid transparent;
}

.bb2b {
  width: 100%;
  height: 100%;
  background: repeating-linear-gradient(
      var(--building-color2),
      var(--building-color2) 6%,
      var(--window-color2) 6%,
      var(--window-color2) 9%
    );
}

.bb3 {
  width: 10%;
  height: 55%;
  background: repeating-linear-gradient(
      90deg,
      var(--building-color3),
      var(--building-color3),
      var(--window-color3) 15%
    );
}

.bb4 {
  width: 11%;
  height: 58%;
}

.bb4a {
  width: 3%;
  height: 10%;
  background-color: var(--building-color4);
}

.bb4b {
  width: 80%;
  height: 5%;
  background-color: var(--building-color4);
}

.bb4c {
  width: 100%;
  height: 85%;
  background-color: var(--building-color4);
}

.bb4-window {
  width: 18%;
  height: 90%;
  background-color: var(--window-color4);
}

/* FOREGROUND BUILDINGS - "fb" stands for "foreground building" */
.fb1 {
  width: 10%;
  height: 60%;
}
--fcc-editable-region--
.fb1a {
  border-bottom: 7vh solid var(--building-color4);
}
--fcc-editable-region--
.fb1b {
  width: 60%;
  height: 10%;
  background-color: var(--building-color4);
}

.fb1c {
  width: 100%;
  height: 80%;
  background: repeating-linear-gradient(
      90deg,
      var(--building-color4),
      var(--building-color4) 10%,
      transparent 10%,
      transparent 15%
    ),
    repeating-linear-gradient(
      var(--building-color4),
      var(--building-color4) 10%,
      var(--window-color4) 10%,
      var(--window-color4) 90%
    );
}

.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);
}

```

