.flipper {
    -webkit-transition: 0.5s;
    -webkit-transform-style: preserve-3d;

    -moz-transition: 0.5s;
    -moz-transform-style: preserve-3d;

    -o-transition: 0.5s;
    -o-transform-style: preserve-3d;

    transition: 0.5s;
    transform-style: preserve-3d;

    position: relative;
}

.flipper.active {
    -webkit-transform: rotateY(180deg);
    -moz-transform: rotateY(180deg);
    -o-transform: rotateY(180deg);
    transform: rotateY(180deg);
}

.front, .back {
    -webkit-backface-visibility: hidden;
    -moz-backface-visibility: hidden;
    -o-backface-visibility: hidden;
    backface-visibility: hidden;

    position: absolute;
    top: 0;
    left: 0;
}

.back {
    -webkit-transform: rotateY(180deg);
    -moz-transform: rotateY(180deg);
    -o-transform: rotateY(180deg);
    transform: rotateY(180deg);

    background: #f8f8f8;
}

@-webkit-keyframes drop{
    0%{top:5px;opacity:0} 
    30%{top:10px;opacity:1} 
    100%{top:25px;opacity:0}
}

@keyframes drop{
    0%{top:5px;opacity:0} 
    30%{top:10px;opacity:1}
    100%{top:25px;opacity:0}
}