---
id: 5d822fd413a79914d39e992b
title: Part 99
challengeType: 0
isBeta: true
---
## Description
Add your `--building-color1` variable as value of the `background-color` property of `fb4b`. Then, remove the `background-color` from `fb4`.
## Instructions
## Tests
```yml
tests:
- text: test-text
testString: const fb4 = code.match(/\.fb4\s*{[\s\S]+?[^}]}/g)[0]; const fb4b = code.match(/\.fb4b\s*{[\s\S]+?[^}]}/g)[0]; assert(!/background-color/g.test(fb4) && /background-color\s*:\s*var\(\s*--building-color1\s*\)\s*(;|})/g.test(fb4b));
```
## Challenge Seed
```html
freeCodeCamp Skyline Project
```