.book{perspective:2000px}.book,.page{display:flex}.page{width:600px;height:850px;background:#fff;justify-content:center;align-items:center;transition:transform .8s ease,box-shadow .8s ease;-webkit-backface-visibility:hidden;backface-visibility:hidden;aspect-ratio:6/8.5}.single-page .page{width:100%;max-width:100%;aspect-ratio:6/8.5;position:relative}.single-page .page img{width:100%;height:100%;object-fit:contain}.flip{transform-origin:left center}.book:hover .flip{box-shadow:0 10px 25px rgba(0,0,0,.2)}.page img{object-fit:contain;width:100%;max-width:100%;aspect-ratio:6/8.5}.btn-back-to-top{position:fixed;bottom:20px;right:20px;z-index:9999;border-radius:50%;width:48px;height:48px;display:flex;justify-content:center;align-items:center;font-size:20px;box-shadow:0 2px 8px rgba(0,0,0,.2);transition:all .3s ease}.btn-back-to-top:hover{transform:translateY(-3px);box-shadow:0 4px 12px rgba(0,0,0,.3)}.hoverButtonPage{opacity:.3}.hoverButtonPage:hover{opacity:1}@media (max-width:991px){.book{flex-direction:column;align-items:center}.page{width:100%;height:auto}}@media (max-width:400px){.page img{max-height:530px}.book{width:100%}}