@import url('https://fonts.googleapis.com/css2?family=Roboto:wght@300;400;500;700;900&display=swap');

        body {
            font-family: 'Roboto', sans-serif;
            background-color: #333;
            margin: 0;
            padding: 0;
            height: 100vh;
            display: flex;
            justify-content: center;
            align-items: center;
            overflow: hidden;
        }

        .flip-book {
            box-shadow: 0 0 20px 0 rgba(0,0,0,0.5);
            display: none;
            background-size: cover;
        }

        .page {
            padding: 0;
            background-color: transparent;
            overflow: hidden;
        }

        .page-content {
            width: 100%;
            height: 100%;
            display: flex;
            justify-content: center;
            align-items: center;
        }

        .page-image {
            width: 100%;
            height: 100%;
            object-fit: contain; 
            display: block;
        }

        #loader {
            position: fixed;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            color: white;
            font-size: 1.5rem;
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: 10px;
        }
        .spinner {
            border: 4px solid rgba(255, 255, 255, 0.3);
            border-radius: 50%;
            border-top: 4px solid white;
            width: 40px;
            height: 40px;
            animation: spin 1s linear infinite;
        }
        @keyframes spin { 0% { transform: rotate(0deg); } 100% { transform: rotate(360deg); } }
        
        .controls {
            position: fixed;
            bottom: 20px;
            left: 50%;
            transform: translateX(-50%);
            display: flex;
            gap: 20px;
            z-index: 100;
        }
        .btn {
            background: rgba(255,255,255,0.2);
            border: 1px solid white;
            color: white;
            padding: 8px 16px;
            border-radius: 20px;
            cursor: pointer;
            backdrop-filter: blur(5px);
            transition: all 0.3s;
        }
        .btn:hover { background: white; color: #333; }