@mixin pulse-darken($delay, $duration, $background){
  animation: bg-color-change $duration infinite ease;
  animation-delay: $delay;
  @keyframes bg-color-change {
    0%  {background: $background}
    50%  {background: darken( $background, 10% )}
    100%  {background: $background}
  }
}

@mixin pulse-lighten($delay, $duration, $background){
  animation: bg-color-change $duration infinite ease;
  animation-delay: $delay;
  @keyframes bg-color-change {
    0%  {background: $background}
    50%  {background: lighten( $background, 10% )}
    100%  {background: $background}
  }
}

@mixin pulse-outline($delay,$duration,$outline-color) {
  animation: pulse-outline-keyframes $duration ease;
  animation-delay: $delay;
  @keyframes pulse-outline-keyframes {
    0% {
      box-shadow: none;
    }
    25% {
      box-shadow: 0 0 3pt 2pt $outline-color;
    }
    60% {
      box-shadow: 0 0 3pt 2pt $outline-color;
    }
    100% {
      box-shadow: none;
    }
  }
}