SCSS (Sass + Compass) Gradient bar

@mixin gradient_bar($base-color: $sh_base, $inverse: FALSE) {
    @if $inverse == TRUE {
        $base-color: invert($base-color);
    }
    background-color: $base-color;
    @include background-image(linear-gradient($base-color, lighten($base-color, $default_color_offset) 40%, lighten($base-color, $default_color_offset) 60%, $base-color));
}