.bb-bookblock {
width: 400px;
height: 300px;
position: relative;
background: #fff;
z-index: 100;
}
.bb-page {
width: 50%;
height: 100%;
left: 50%;
position: absolute;
-webkit-transform-style: preserve-3d;
-moz-transform-style: preserve-3d;
-o-transform-style: preserve-3d;
-ms-transform-style: preserve-3d;
transform-style: preserve-3d;
-webkit-transform-origin: left center;
-moz-transform-origin: left center;
-o-transform-origin: left center;
-ms-transform-origin: left center;
transform-origin: left center;
}
.bb-page > div,
.bb-outer,
.bb-content {
position: absolute;
height: 100%;
top: 0;
left: 0;
}
.bb-content {
background: #fff;
}
.bb-inner {
position: relative;
width: 100%;
height: 100%;
}
.bb-overlay, .bb-outer {
-webkit-backface-visibility: hidden;
-moz-backface-visibility: hidden;
-o-backface-visibility: hidden;
-ms-backface-visibility: hidden;
backface-visibility: hidden;
}
.bb-page > div {
width: 100%;
-webkit-transform-style: preserve-3d;
-moz-transform-style: preserve-3d;
-o-transform-style: preserve-3d;
-ms-transform-style: preserve-3d;
transform-style: preserve-3d;
-webkit-backface-visibility: hidden;
-moz-backface-visibility: hidden;
-o-backface-visibility: hidden;
-ms-backface-visibility: hidden;
backface-visibility: hidden;
}
.bb-back {
-webkit-transform: rotateY(-180deg);
-moz-transform: rotateY(-180deg);
-o-transform: rotateY(-180deg);
-ms-transform: rotateY(-180deg);
transform: rotateY(-180deg);
}
.bb-outer {
width: 100%;
overflow: hidden;
z-index: 999;
}
.bb-overlay, 
.bb-flipoverlay {
background-color: rgba(0, 0, 0, 0.7);
position: absolute;
top: 0px;
left: 0px;
width: 100%;
height: 100%;
opacity: 0;
z-index: 1000;
}
.bb-flipoverlay {
background-color: rgba(0, 0, 0, 0.2);
}
.bb-bookblock > div.bb-page:first-child,
.bb-bookblock > div.bb-page:first-child .bb-back {
-webkit-transform: rotateY(180deg);
-moz-transform: rotateY(180deg);
-o-transform: rotateY(180deg);
-ms-transform: rotateY(180deg);
transform: rotateY(180deg);
}
.js .bb-item {
width: 100%;
height: 100vh;
position: absolute;
top: 0;
left: 0;
display: none;
background: #fff;
padding-bottom: 70px;
}