_material-design-shadow-sass-fanction.scss

$shadow-x-ratio:    0.375 !default;
$shadow-y-ratio:    0.375 !default;
$shadow-blur-lower: 1 !default;
$shadow-blur-ratio: 1 !default;
$shadow-color:      #000000 !default;
$shadow-alpha-init: 0.375 !default;
$shadow-alpha-lower: 0.175 !default;
$shadow-alpha-ratio: 0.005 !default;

@function layer-shadow( $dp: 0, $x: 0px, $y: 1px, $blur: 1px ) {
  $box-shadow: false;

  $shadow-x: $x;
  $shadow-y: $y;
  $shadow-blur: $blur;

  //shadow angle
  $result-shadow-x: $shadow-x * if($shadow-x-ratio * abs($dp) > 1, ($shadow-x-ratio * $dp), $dp);
  $result-shadow-y: $shadow-y * if($shadow-y-ratio * abs($dp) > 1, ($shadow-y-ratio * $dp), $dp);

  //shadow color
  $result-shadow-alpha: $shadow-alpha-init - ($dp * $shadow-alpha-ratio);
  $result-shadow-color: rgba($shadow-color, if($result-shadow-alpha >= $shadow-alpha-lower, $result-shadow-alpha, $shadow-alpha-lower ));

  //shadow blur
  $result-shadow-blur-size: $shadow-blur * if($shadow-blur-ratio * abs($dp) > 1, $shadow-blur-ratio * abs($dp), 1);

  @if $dp < 0 {
    $box-shadow: inset (- floor($result-shadow-x)) (- floor($result-shadow-y)) floor($result-shadow-blur-size) $result-shadow-color;
  } @else if $dp == 0 {
    $box-shadow: none;
  } @else if $dp > 0 {
    $box-shadow: floor($result-shadow-x) floor($result-shadow-y) floor($result-shadow-blur-size) $result-shadow-color;
  }

  @return $box-shadow;
}