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

        body {
            font-family: 'Hind Siliguri', sans-serif;
            background: linear-gradient(135deg, #1a2980, #26d0ce);
            min-height: 100vh;
            color: #333;
        }

        .app-container {
            max-width: 1200px;
            margin: 0 auto;
            padding: 20px;
        }

        header {
            text-align: center;
            padding: 30px 0;
            color: white;
            animation: fadeInDown 1s ease;
        }

        header h1 {
            font-size: 2.5rem;
            margin-bottom: 10px;
            text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.3);
        }

        header p {
            font-size: 1.2rem;
            opacity: 0.9;
        }

        .class-grid {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
            gap: 30px;
            margin-top: 40px;
        }

        .class-card {
            background: white;
            border-radius: 15px;
            overflow: hidden;
            box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
            transition: transform 0.3s ease, box-shadow 0.3s ease;
            animation: fadeInUp 0.8s ease forwards;
            opacity: 0;
            position: relative;
        }

        .class-card:nth-child(1) { animation-delay: 0.1s; }
        .class-card:nth-child(2) { animation-delay: 0.2s; }
        .class-card:nth-child(3) { animation-delay: 0.3s; }
        .class-card:nth-child(4) { animation-delay: 0.4s; }
        .class-card:nth-child(5) { animation-delay: 0.5s; }
        .class-card:nth-child(6) { animation-delay: 0.6s; }

        .class-card:hover {
            transform: translateY(-10px);
            box-shadow: 0 15px 30px rgba(0, 0, 0, 0.2);
        }

        .class-header {
            background: linear-gradient(to right, #4facfe, #00f2fe);
            padding: 20px;
            color: white;
            position: relative;
        }

        .class-title {
            font-size: 1.5rem;
            font-weight: 600;
            margin-bottom: 5px;
        }

        .class-subtitle {
            font-size: 1rem;
            opacity: 0.9;
        }

        .lock-icon {
            position: absolute;
            top: 20px;
            right: 20px;
            font-size: 1.5rem;
            opacity: 0.8;
        }

        .class-content {
            padding: 20px;
        }

        .class-description {
            margin-bottom: 15px;
            line-height: 1.6;
        }

        .class-btn {
            background: linear-gradient(to right, #4facfe, #00f2fe);
            color: white;
            border: none;
            padding: 12px 20px;
            border-radius: 30px;
            font-size: 1rem;
            font-weight: 500;
            cursor: pointer;
            transition: all 0.3s ease;
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 8px;
        }

        .class-btn:hover {
            transform: scale(1.05);
            box-shadow: 0 5px 15px rgba(79, 172, 254, 0.4);
        }

        .modal {
            display: none;
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background-color: rgba(0, 0, 0, 0.7);
            z-index: 1000;
            animation: fadeIn 0.3s ease;
        }

        .modal-content {
            background-color: white;
            margin: 50px auto;
            padding: 30px;
            width: 90%;
            max-width: 600px;
            border-radius: 15px;
            box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
            animation: slideIn 0.5s ease;
            max-height: 80vh;
            overflow-y: auto;
        }

        .close-btn {
            color: #aaa;
            float: right;
            font-size: 28px;
            font-weight: bold;
            cursor: pointer;
            transition: color 0.3s ease;
        }

        .close-btn:hover {
            color: #333;
        }

        .passkey-form {
            margin-top: 20px;
        }

        .form-group {
            margin-bottom: 20px;
        }

        .form-group label {
            display: block;
            margin-bottom: 8px;
            font-weight: 500;
        }

        .form-group input {
            width: 100%;
            padding: 12px;
            border: 1px solid #ddd;
            border-radius: 8px;
            font-size: 1rem;
            transition: border-color 0.3s ease;
        }

        .form-group input:focus {
            border-color: #4facfe;
            outline: none;
        }

        .submit-btn {
            background: linear-gradient(to right, #4facfe, #00f2fe);
            color: white;
            border: none;
            padding: 12px 25px;
            border-radius: 30px;
            font-size: 1rem;
            font-weight: 500;
            cursor: pointer;
            transition: all 0.3s ease;
        }

        .submit-btn:hover {
            transform: scale(1.05);
            box-shadow: 0 5px 15px rgba(79, 172, 254, 0.4);
        }

        .error-message {
            color: #e74c3c;
            margin-top: 10px;
            font-size: 0.9rem;
            display: none;
        }

        .video-container {
            display: none;
            margin-top: 20px;
        }

        .video-list {
            display: grid;
            gap: 15px;
        }

        .video-item {
            background: #f9f9f9;
            border-radius: 10px;
            padding: 15px;
            display: flex;
            align-items: center;
            gap: 15px;
            transition: all 0.3s ease;
        }

        .video-item:hover {
            background: #f0f0f0;
            transform: translateX(5px);
        }

        .video-thumbnail {
            width: 120px;
            height: 80px;
            border-radius: 8px;
            overflow: hidden;
            position: relative;
        }

        .video-thumbnail img {
            width: 100%;
            height: 100%;
            object-fit: cover;
        }

        .video-play-icon {
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            color: white;
            font-size: 1.5rem;
            background-color: rgba(0, 0, 0, 0.5);
            width: 40px;
            height: 40px;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .video-info {
            flex: 1;
        }

        .video-title {
            font-weight: 600;
            margin-bottom: 5px;
        }

        .video-duration {
            color: #666;
            font-size: 0.9rem;
        }

        .video-player {
            width: 100%;
            border-radius: 10px;
            margin-top: 20px;
            display: none;
        }

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

        @keyframes fadeInDown {
            from {
                opacity: 0;
                transform: translateY(-30px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }

        @keyframes fadeInUp {
            from {
                opacity: 0;
                transform: translateY(30px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }

        @keyframes slideIn {
            from {
                transform: translateY(-50px);
                opacity: 0;
            }
            to {
                transform: translateY(0);
                opacity: 1;
            }
        }

        .success-message {
            background-color: #2ecc71;
            color: white;
            padding: 10px 15px;
            border-radius: 8px;
            margin-top: 15px;
            display: none;
            animation: fadeIn 0.5s ease;
        }

        .class-badge {
            position: absolute;
            top: -10px;
            right: -10px;
            background: #e74c3c;
            color: white;
            border-radius: 50%;
            width: 30px;
            height: 30px;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 0.8rem;
            font-weight: bold;
        }
         /* Responsive */
        @media (max-width: 768px) {
            .content-grid {
                grid-template-columns: 1fr;
            }

}

        @media (max-width: 768px) {
            header h1 {
                font-size: 2rem;
            }
            
            .class-grid {
                grid-template-columns: 1fr;
            }
        }