---
id: 5d822fd413a79914d39e98df
title: Part 23
challengeType: 0
isHidden: true
---
## 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`.
## Instructions
## Tests
```yml
tests:
- text: test-text
testString: 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));
```
## Challenge Seed
```html
freeCodeCamp Skyline Project
```