:root {
    --bg-color: #0f172a;
    --accent-color: #f97316; /* Naranja Hotmart */
}

body {
    /* Degradado vívido y moderno */
    background: linear-gradient(135deg, #0f172a 0%, #1e1b4b 50%, #312e81 100%);
    background-attachment: fixed; /* Para que el fondo no se mueva al hacer scroll */
    color: white;
    font-family: 'Inter', sans-serif;
    display: flex;
    flex-direction: column;
    align-items: center;
    min-height: 100vh;
    margin: 0;
}

.library-container {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 80px;
    padding: 100px 20px;
}

.book-card {
    perspective: 1000px;
    text-align: center;
}

.book-inner {
    width: 200px;
    height: 300px;
    position: relative;
    transform-style: preserve-3d;
    transition: transform 0.7s cubic-bezier(0.4, 0, 0.2, 1);
    transform-origin: left;
}

.book-card:hover .book-inner {
    transform: rotateY(-120deg);
}

.book-front {
    position: absolute;
    width: 100%;
    height: 100%;
    z-index: 2;
    backface-visibility: hidden;
}

.book-front img {
    width: 100%;
    height: 100%;
    border-radius: 0 4px 4px 0;
    box-shadow: 5px 5px 15px rgba(0,0,0,0.5);
}

.book-pages {
    position: absolute;
    width: 100%;
    height: 98%;
    background: #fff;
    top: 1%;
    left: 2px;
    z-index: 1;
    border-radius: 0 4px 4px 0;
    box-shadow: inset -5px 0 10px rgba(0,0,0,0.1);
}

/* Estilo de Botones */
.btn-read, .btn-buy {
    margin-top: 30px;
    padding: 12px 24px;
    border: none;
    border-radius: 8px;
    font-weight: bold;
    cursor: pointer;
    text-decoration: none;
    display: block;
    transition: 0.3s;
}

.btn-read { background: #3b82f6; color: white; }
.btn-buy { background: var(--accent-color); color: white; }