_linear-gradient.scss

@mixin linear-gradient($pos, $G1, $G2: false,
                       $G3: false, $G4: false,
                       $G5: false, $G6: false,
                       $G7: false, $G8: false,
                       $G9: false, $G10: false,
                       $deprecated-pos1: left top,
                       $deprecated-pos2: left bottom,
                       $fallback: false) {
  // Detect what type of value exists in $pos
  $pos-type: type-of(nth($pos, 1));
  $pos-spec: null;
  $pos-degree: null;

  // If $pos is missing from mixin, reassign vars and add default position
  @if ($pos-type == color) or (nth($pos, 1) == "transparent")  {
    $G10: $G9; $G9: $G8; $G8: $G7; $G7: $G6; $G6: $G5;
     $G5: $G4; $G4: $G3; $G3: $G2; $G2: $G1; $G1: $pos;
     $pos: null;
  }

  @if $pos {
    $positions: _linear-positions-parser($pos);
    $pos-degree: nth($positions, 1);
    $pos-spec:   nth($positions, 2);
  }

  $full: compact($G1, $G2, $G3, $G4, $G5, $G6, $G7, $G8, $G9, $G10);

  // Set $G1 as the default fallback color
  $fallback-color: nth($G1, 1);

  // If $fallback is a color use that color as the fallback color
  @if (type-of($fallback) == color) or ($fallback == "transparent") {
    $fallback-color: $fallback;
  }

  background-color: $fallback-color;
  background-image: deprecated-webkit-gradient(linear, $deprecated-pos1, $deprecated-pos2, $full); // Safari <= 5.0
  background-image:  -webkit-linear-gradient($pos-degree $full); // Safari 5.1+, Chrome
  background-image: unquote("linear-gradient(#{$pos-spec}#{$full})");
}

// Helper Function
@function _flip-position($pos) {
 @return if($pos == left, right, null)
         if($pos == right, left, null)
         if($pos == top, bottom, null)
         if($pos == bottom, top, null);
}