---
id: 5d822fd413a79914d39e98fb
title: Part 51
challengeType: 0
dashedName: part-51
---

# --description--

You can make an instant color change in a gradient by giving the transition zero space like this:

```css
gradient-type(
  color1,
  color1 50%,
  color2 50%,
  color2
);
```

Here, the top half of the element will be `color1` and the bottom half will be `color2`. Add a `linear-gradient` to `.bb2b` that uses `--building-color2` from `0%` to `6%` and `--window-color2` from `6%` to `9%`.

# --hints--

You should give `.bb2b` a `background` property.

```js
assert.isNotEmpty(new __helpers.CSSHelp(document).getStyle(`.bb2b`)?.background);
```

You should use a `linear-gradient` on the `background`.

```js
assert.include(new __helpers.CSSHelp(document).getStyle(`.bb2b`)?.background, "linear-gradient");
```

You should use `--building-color2` from `0%` to `6%`.

```js
assert.match(new __helpers.CSSHelp(document).getStyle(`.bb2b`)?.getPropVal('background', true), /var\(--building-color2\)(0%)?,var\(--building-color2\)6%/);
```

You should use `--window-color2` from `6%` to `9%`.

```js
assert.include(new __helpers.CSSHelp(document).getStyle(`.bb2b`)?.getPropVal('background', true), "var(--window-color2)6%,var(--window-color2)9%");
```

`.bb2b` should have a `linear-gradient` transitioning from `--building-color2` at `0%` to `6%`, and `--window-color2` at `6%` to `9%`.

```js
assert.match(new __helpers.CSSHelp(document).getStyle(`.bb2b`)?.getPropVal('background', true), /linear-gradient\(var\(--building-color2\)(0%)?,var\(--building-color2\)6%,var\(--window-color2\)6%,var\(--window-color2\)9%\)/);
```

# --seed--

## --seed-contents--

```html
<!DOCTYPE html>
<html>    
  <head>
    <title>freeCodeCamp Skyline Project</title>
    <link href="styles.css" rel="stylesheet" type="text/css" />   
  </head>

  <body>
    <div class="background-buildings">
      <div></div>
      <div></div>
      <div class="bb1">
        <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"></div>
      <div></div>
      <div></div>
    </div>

    <div class="foreground-buildings">
      <div></div>
      <div></div>
      <div class="fb1"></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;
}

* {
  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;
}

/* BACKGROUND BUILDINGS - "bb" stands for "background building" */
.bb1 {
  width: 10%;
  height: 70%;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.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%;
  background-color: var(--building-color2);
}
--fcc-editable-region--
.bb2b {
  width: 100%;
  height: 100%;
}
--fcc-editable-region--
.bb3 {
  width: 10%;
  height: 55%;
  background-color: var(--building-color3);
}

.bb4 {
  width: 11%;
  height: 58%;
  background-color: var(--building-color4);
}

/* FOREGROUND BUILDINGS - "fb" stands for "foreground building" */
.fb1 {
  width: 10%;
  height: 60%;
  background-color: var(--building-color4);
}

.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);
}
    
```

