---
id: 5d822fd413a79914d39e98df
title: Part 23
challengeType: 0
dashedName: part-23
---

# --description--

Hmm, I'm not sure why that didn't work. You can add a fallback value to a variable by putting it as the second value of where you use the variable like this: `var(--variable-name, fallback-value)`. The property will use the fallback value when there's a problem with the variable. Add a fallback value of `green` to the `background-color` of `bb2`.

# --hints--

test-text

```js
const bb2style = code.match(/\.bb2\s*{[\s\S]+?[^}]}/g)[0];
assert(
  /background-color\s*:\s*var\(\s*--building-color2\s*,\s*green\s*\)\s*(;|\s*})/g.test(
    bb2style
  )
);
```

# --seed--

## --seed-contents--

```html
<!DOCTYPE html>
<html>    
  <head>
    <title>freeCodeCamp Skyline Project</title>
    <style>
      * {
        border: 1px solid black;
        box-sizing: border-box;
      }

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

      .background-buildings {
        width: 100%;
        height: 100%;
        display: flex;
        align-items: flex-end;
        justify-content: space-evenly;
      }

      .bb1 {
        width: 10%;
        height: 70%;
        display: flex;
        flex-direction: column;
        align-items: center;
        --building-color1: #aa80ff;
        --building-color2: #66cc99;
      }

      .bb1a {
        width: 70%;
        height: 10%;
        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);
      }

      .bb2 {
        width: 10%;
        height: 50%;
        background-color: var(--building-color2);
      }

      .bb3 {
        width: 10%;
        height: 55%;
      }

      .bb4 {
        width: 11%;
        height: 58%;
      }
    </style>
  </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>
  </body>
</html>
```

# --solutions--

```html
<!DOCTYPE html>
<html>    
  <head>
    <title>freeCodeCamp Skyline Project</title>
    <style>
      * {
        border: 1px solid black;
        box-sizing: border-box;
      }

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

      .background-buildings {
        width: 100%;
        height: 100%;
        display: flex;
        align-items: flex-end;
        justify-content: space-evenly;
      }

      .bb1 {
        width: 10%;
        height: 70%;
        display: flex;
        flex-direction: column;
        align-items: center;
        --building-color1: #aa80ff;
        --building-color2: #66cc99;
      }

      .bb1a {
        width: 70%;
        height: 10%;
        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);
      }

      .bb2 {
        width: 10%;
        height: 50%;
        background-color: var(--building-color2, green);
      }

      .bb3 {
        width: 10%;
        height: 55%;
      }

      .bb4 {
        width: 11%;
        height: 58%;
      }
    </style>
  </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>
  </body>
</html>
```
