---
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
freeCodeCamp Skyline Project
```
# --solutions--
```html
freeCodeCamp Skyline Project
```