demo.scss

demo.scss

$bgColor: #DEDBEE;

%clear {
  *zoom: 1;
  &:before, &:after {
    content: ' ';
    display: table;
  }
  &:after {
    clear: both;
  }
}

body {
  background: $bgColor;
  color: invert($bgColor);
}

.alert {
  background: yellow;
  color: red;
  border: 1px solid black;
  @extend %clear;
}

.alert-muted {
  @extend .alert;
  color: #111111;
  padding: 1em;
}