$cutout-size: 5px !default;
$cutout-blur: 5px !default;

@mixin cutout(
    $size: 5px,
    $blur: 5px
) {
    @include box-shadow(cutout($size, $blur))
}

@function cutout(
    $depth: 5px,
    $blur: 5px
) {
    @return
        0 1px 0 rgba(255,255,255,.2),
        inset 0 $depth ($blur) rgba(0,0,0,.6),
        inset 0 1px $blur rgba(0,0,0,.6)
}