body {
    font-family: 'Inter', sans-serif;
    background-color: #FDFBF8;
    color: #4A4A4A;
}
.active-btn {
    transform: translateY(-2px);
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
}
.book {
    transition: all 0.5s ease-in-out;
    width: 50px;
    height: 70px;
    background-color: #A8DADC;
    border-radius: 4px;
    position: absolute;
    bottom: 20px;
    box-shadow: 2px 2px 5px rgba(0,0,0,0.1);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    color: white;
}
.shelf {
    position: absolute;
    bottom: 10px;
    left: 10%;
    right: 10%;
    height: 10px;
    background-color: #8D6E63;
    border-radius: 4px;
}
.fade-in {
    animation: fadeIn 0.5s ease-in-out forwards;
}
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}