underline.scss

// Underline
@mixin underline($color, $width) {
    background:
        linear-gradient(
            to top,
            $color,
            $color #{$width}em,
            transparent #{$width}em,
            transparent
        ) repeat-x;
    }
a {
    @include underline(currentColor, 0.09);
    color:$blue;
    text-decoration:none;
    }