:root {
            --primary: #6366f1;
            --primary-dark: #4f46e5;
            --primary-light: #818cf8;
            --secondary: #ec4899;
            --bg: #0f172a;
            --bg-card: #1e293b;
            --text-main: #f1f5f9;
            --text-muted: #94a3b8;
            --border: #334155;
            --accent-red: #ef4444;
            --accent-green: #10b981;
            --accent-yellow: #f59e0b;
            --accent-blue: #3b82f6;
            --radius: 16px;
            --shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
            --shadow-sm: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
            --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
        }

        * { 
            box-sizing: border-box; 
            margin: 0;
            padding: 0;
        }

        body { 
            font-family: 'Inter', sans-serif; 
            background: linear-gradient(135deg, #0f172a 0%, #1e1b4b 100%);
            color: var(--text-main);
            min-height: 100vh;
            padding: 0;
            margin: 0;
        }

        /* Glassmorphism Navbar */
        .navbar {
            background: rgba(15, 23, 42, 0.8);
            backdrop-filter: blur(20px);
            border-bottom: 1px solid rgba(99, 102, 241, 0.2);
            padding: 0.5rem 0.5rem;
            position: sticky;
            top: 0;
            z-index: 1000;
            box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
        }

        .nav-container {
            max-width: 1400px;
            margin: 0 auto;
            display: flex;
            justify-content: space-between;
            align-items: center;
            gap: 10px;
        }

        .logo {
            display: flex;
            align-items: center;
            gap: 12px;
            font-size: 1.4rem;
            font-weight: 600;
            background: linear-gradient(135deg, #6366f1, #ec4899);
            -webkit-background-clip: text;
            background-clip: text;
            color: transparent;
        }

        .logo i {
            background: none;
            -webkit-background-clip: unset;
            background-clip: unset;
            color: var(--primary);
        }

        .user-badge {
            display: flex;
            align-items: center;
            gap: 12px;
            background: rgba(99, 102, 241, 0.1);
            padding: 8px 16px;
            border-radius: 40px;
            border: 1px solid rgba(99, 102, 241, 0.3);
        }

        .user-badge i {
            color: var(--primary-light);
        }

        .user-email {
            font-size: 0.875rem;
            color: var(--text-muted);
        }

        .container {
            max-width: 1400px;
            margin: 0 auto;
            padding: 2rem;
        }

        /* Header Section */
        .library-header {
            margin-bottom: 2rem;
            animation: fadeInUp 0.6s ease;
        }

         .library-header h1{
              font-size: 1.5rem;
              margin-bottom: 0.5rem;
        }

        .stats-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
            gap: 1rem;
            margin-top: 1.5rem;
        }

        .stat-card {
            background: var(--bg-card);
            border-radius: var(--radius);
            padding: 1.25rem;
            border: 1px solid var(--border);
            transition: var(--transition);
        }

        .stat-card:hover {
            transform: translateY(-4px);
            border-color: var(--primary);
        }

        .stat-value {
            font-size: 2rem;
            font-weight: 800;
            background: linear-gradient(135deg, var(--primary-light), var(--secondary));
            -webkit-background-clip: text;
            background-clip: text;
            color: transparent;
        }

        .stat-label {
            color: var(--text-muted);
            font-size: 0.875rem;
            margin-top: 0.5rem;
        }

        /* Grid System Mejorado */
        .grid-biblioteca {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(380px, 1fr));
            gap: 1.5rem;
            animation: fadeIn 0.8s ease;
        }

        @media (max-width: 768px) {
            .grid-biblioteca {
                grid-template-columns: 1fr;
            }
            .container {
                padding: 1rem;
            }
        }

        /* Card Design Premium */
        .libro-card {
            background: var(--bg-card);
            border-radius: var(--radius);
            border: 1px solid var(--border);
            overflow: hidden;
            transition: var(--transition);
            position: relative;
            cursor: pointer;
        }

        .libro-card::before {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            height: 3px;
            background: linear-gradient(90deg, var(--primary), var(--secondary));
            transform: scaleX(0);
            transition: transform 0.3s ease;
        }

        .libro-card:hover::before {
            transform: scaleX(1);
        }

        .libro-card:hover {
            transform: translateY(-8px);
            border-color: var(--primary);
            box-shadow: var(--shadow);
        }

        /* Notificación mejorada */
        .notificacion-lectura {
            position: absolute;
            top: 16px;
            right: 16px;
            width: 48px;
            height: 48px;
            background: linear-gradient(135deg, var(--accent-red), #dc2626);
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            z-index: 10;
            animation: pulse 2s infinite;
            box-shadow: 0 0 20px rgba(239, 68, 68, 0.5);
        }

        .notificacion-lectura i {
            color: white;
            font-size: 1.25rem;
        }

        @keyframes pulse {
            0%, 100% { transform: scale(1); opacity: 1; }
            50% { transform: scale(1.1); opacity: 0.9; }
        }

        .portada-wrapper {
            position: relative;
            height: 240px;
            overflow: hidden;
            background: linear-gradient(135deg, #1e293b, #0f172a);
        }

        .portada-img {
            width: 100%;
             aspect-ratio: 2 / 3;
             border-radius: 20px;
             object-fit: cover;
             box-shadow: 0 20px 40px rgba(0, 0, 0, 0.6);
             border: 1px solid rgba(255, 255, 255, 0.1);
        }

        .libro-card:hover .portada-img {
            transform: scale(1.05);
        }

        .libro-info {
            padding: 1.25rem;
        }

        .libro-header h3 {
            font-size: 1.125rem;
            font-weight: 700;
            margin-bottom: 0.25rem;
            color: var(--text-main);
        }

        .autor {
            color: var(--primary-light);
            font-size: 0.875rem;
            margin-bottom: 1rem;
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }

        /* Progreso mejorado */
        .progreso-container {
            margin: 1rem 0;
        }

        .progreso-header {
            display: flex;
            justify-content: space-between;
            font-size: 0.75rem;
            color: var(--text-muted);
            margin-bottom: 0.5rem;
        }

        .progress-bar {
            background: var(--border);
            border-radius: 20px;
            overflow: hidden;
            height: 8px;
        }

        .progress-fill {
            background: linear-gradient(90deg, var(--primary), var(--secondary));
            height: 100%;
            border-radius: 20px;
            transition: width 0.3s ease;
            position: relative;
            overflow: hidden;
        }

        .progress-fill::after {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            bottom: 0;
            right: 0;
            background: linear-gradient(90deg, transparent, rgba(255,255,255,0.3), transparent);
            animation: shimmer 2s infinite;
        }

        @keyframes shimmer {
            0% { transform: translateX(-100%); }
            100% { transform: translateX(100%); }
        }

        .alerta-novedad {
            background: linear-gradient(135deg, rgba(239, 68, 68, 0.1), rgba(239, 68, 68, 0.05));
            border-left: 3px solid var(--accent-red);
            padding: 0.75rem;
            border-radius: 8px;
            margin: 1rem 0;
            font-size: 0.813rem;
        }

        .alerta-novedad i {
            color: var(--accent-red);
            margin-right: 0.5rem;
        }

        .al-dia {
            background: linear-gradient(135deg, rgba(16, 185, 129, 0.1), rgba(16, 185, 129, 0.05));
            border-left: 3px solid var(--accent-green);
            padding: 0.75rem;
            border-radius: 8px;
            margin: 1rem 0;
            font-size: 0.813rem;
        }

        .btn {
            display: inline-flex;
            align-items: center;
            justify-content: center;
            gap: 0.5rem;
            width: 100%;
            padding: 0.75rem;
            border-radius: 12px;
            text-decoration: none;
            font-weight: 600;
            font-size: 0.875rem;
            transition: var(--transition);
            border: none;
            cursor: pointer;
        }

        .btn-primary {
            background: linear-gradient(135deg, var(--primary), var(--primary-dark));
            color: white;
        }

        .btn-primary:hover {
            transform: translateY(-2px);
            box-shadow: 0 10px 20px rgba(99, 102, 241, 0.3);
        }

        /* Estados de carga */
        .loading-state {
            text-align: center;
            padding: 4rem;
            grid-column: 1 / -1;
        }

        .spinner {
            width: 50px;
            height: 50px;
            border: 3px solid var(--border);
            border-top-color: var(--primary);
            border-radius: 50%;
            animation: spin 1s linear infinite;
            margin: 0 auto 1rem;
        }

        @keyframes spin {
            to { transform: rotate(360deg); }
        }

        .empty-state {
            text-align: center;
            padding: 4rem;
            grid-column: 1 / -1;
        }

        .empty-state i {
            font-size: 4rem;
            color: var(--text-muted);
            margin-bottom: 1rem;
        }

        .hidden {
            display: none;
        }

        @keyframes fadeIn {
            from { opacity: 0; }
            to { opacity: 1; }
        }

        @keyframes fadeInUp {
            from {
                opacity: 0;
                transform: translateY(20px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }

        /* Skeleton Loading */
        .skeleton {
            background: linear-gradient(90deg, var(--bg-card) 25%, var(--border) 50%, var(--bg-card) 75%);
            background-size: 200% 100%;
            animation: loading 1.5s infinite;
        }

        @keyframes loading {
            0% { background-position: 200% 0; }
            100% { background-position: -200% 0; }
        }