sass-showcase.scss

$green: #00ff80;

@mixin square($size: 100%) {
  width: $size;
  height: $size;
}

html, body {
  @include square;
}

.greenButton {
  background-color: $green;
  color: white;

  &:hover {
    background-color: darken(white, 10%);
    color: $green;
  }

  .icon {
    @include square(16px);
    background-image: url(images/icon.png);
  }
}