Extend One Set of CSS Styles to Another Element

Sass has a feature called extend that makes it easy to borrow the CSS rules from one element and build upon them in another.

For example, the below block of CSS rules style a .panel class. It has a background-color, height and border.

.panel{
  background-color: red;
  height: 70px;
  border: 2px solid green;
}

Now you want another panel called .big-panel. It has the same base properties as .panel, but also needs a width and font-size. It's possible to copy and paste the initial CSS rules from .panel, but the code becomes repetitive as you add more types of panels. The extend directive is a simple way to reuse the rules written for one element, then add more for another:

.big-panel{
  @extend .panel;
  width: 150px;
  font-size: 2em;
}

The .big-panel will have the same properties as .panel in addition to the new styles.

Make a class .info-important that extends .info and also has a background-color set to magenta.