Sass Button Mixin - Inspired by Bourbon button mixin

gistfile1.scss

/*------------------------------------*\
    Auto Button Mixin
\*------------------------------------*/

@mixin button(  $base-color: #f9f9f9,
                $radius: 4px,
                $bold: true,
                $drop-shadow: true,
                $padding: '.5em 1.5em'){

    $color:             hsl(0, 0, 100%);
    $border:            adjust-color($base-color, $lightness: -20%);
    $inset-shadow:      adjust-color($base-color, $lightness:  15%);
    $stop-gradient:     adjust-color($base-color, $lightness: -8%);
    $text-shadow:       -1px -1px 0 adjust-color($base-color, $lightness: -20%);
    $drop-shadow-c:     '';

    @if lightness($base-color) > 70% {
        $color:       hsl(0, 0, 20%);
        $text-shadow: 1px 1px 0 adjust-color($base-color, $lightness: 4%);
    }

    @if $drop-shadow == true{
        $drop-shadow-c: ', 0 1px 3px rgba(0,0,0,.1)';
    }

    @include border-radius($radius);
    @include box-shadow(inset 0 1px 0 0 $inset-shadow unquote($drop-shadow-c));
    @include background-image(linear-gradient($base-color, $stop-gradient));

    -webkit-background-clip: padding-box;
    background-color:$base-color;
    border: 1px solid $border;
    color: $color;
    display: inline-block;
    padding:unquote($padding);
    text-decoration: none;
    text-shadow: $text-shadow;
    @if $bold == true {
        font-weight:bold;
    }

    &:hover {
        $color:         hsl(0, 0, 100%);

        @if lightness($base-color) > 70% {
          $color:       hsl(0, 0, 10%);
        }

        $base-color-hover:      adjust-color($base-color, $lightness: -2%);
        $inset-shadow-hover:    adjust-color($base-color, $lightness:  5%);
        $stop-gradient-hover:   adjust-color($base-color, $lightness: -10%);

        @include box-shadow(inset 0 1px 0 0 $inset-shadow-hover unquote($drop-shadow-c));
        @include background-image(linear-gradient($base-color-hover, $stop-gradient-hover));
        cursor: pointer;
        color: $color;
        background-color:$base-color-hover;
    }

    &:active {
        $inset-shadow-active: adjust-color($base-color, $lightness: -8%);

        @include box-shadow(inset 0 0 8px 4px $inset-shadow-active,
                            inset 0 0 8px 4px $inset-shadow-active,
                            0 1px 1px 0 #eee unquote($drop-shadow-c));
    }
}