@mixin where($sel: null) {
    @if ( "&" == $sel ) {
        h1 { color: white; }
    } @else {
        h1 { color: blue; }
    }
}
.hive { @include where(); } 
.bee { @include where(&); } 
.amp { @include where(".amp"); } 
.queen { @include where("&"); } 
