

@include keyframes ( flip-vertical-left ) {
    0% {
        @include transform( rotateY(0) );
    }
    100% {
        @include transform( rotateY(-180deg) );
    }
}

@include keyframes( flip-vertical-right ){
    0% {
        @include transform( rotateY(0) );
    }
    100% {
        @include transform( rotateY(180deg) );
    }
}
  