* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            transition: all 0.3s ease;
        }
        
        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            background: linear-gradient(135deg, #E3F2FD 0%, #F3E5F5 25%, #E8F5E9 50%, #FFF9C4 75%, #FCE4EC 100%);
            background-attachment: fixed;
            min-height: 100vh;
            color: #2c3e50;
            position: relative;
        }
        
        /* Notification System - FIXED */
        #notificationContainer {
            position: fixed;
            top: 20px;
            right: 20px;
            z-index: 100000;
            display: flex;
            flex-direction: column;
            gap: 10px;
            pointer-events: none;
        }
        
        .notification {
            padding: 15px 25px;
            border-radius: 10px;
            box-shadow: 0 5px 20px rgba(0, 0, 0, 0.2);
            animation: slideIn 0.3s ease;
            font-weight: 500;
            min-width: 250px;
            max-width: 400px;
            display: flex;
            align-items: center;
            gap: 10px;
            pointer-events: all;
        }
        
        @keyframes slideIn {
            from {
                transform: translateX(400px);
                opacity: 0;
            }
            to {
                transform: translateX(0);
                opacity: 1;
            }
        }
        
        @keyframes slideOut {
            from {
                transform: translateX(0);
                opacity: 1;
            }
            to {
                transform: translateX(400px);
                opacity: 0;
            }
        }
        
        .notification.success {
            background: linear-gradient(135deg, #4CAF50 0%, #45a049 100%);
            color: white;
        }
        
        .notification.error {
            background: linear-gradient(135deg, #f44336 0%, #da190b 100%);
            color: white;
        }
        
        .notification.info {
            background: linear-gradient(135deg, #2196F3 0%, #1976D2 100%);
            color: white;
        }
        
        .notification.warning {
            background: linear-gradient(135deg, #ff9800 0%, #e68900 100%);
            color: white;
        }
        
        .notification.hide {
            animation: slideOut 0.3s ease;
        }
        
        /* Loading Overlay */
        .loading-overlay {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background: rgba(0, 0, 0, 0.5);
            display: flex;
            justify-content: center;
            align-items: center;
            z-index: 99999;
            display: none;
        }
        
        .loading-overlay.active {
            display: flex;
        }
        
        .loading-spinner {
            width: 50px;
            height: 50px;
            border: 5px solid #f3f3f3;
            border-top: 5px solid #667eea;
            border-radius: 50%;
            animation: spin 1s linear infinite;
        }
        
        @keyframes spin {
            0% { transform: rotate(0deg); }
            100% { transform: rotate(360deg); }
        }
        
        /* Subtle animated background dots */
        body::before {
            content: '';
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background-image: 
                radial-gradient(circle at 20% 50%, rgba(120, 119, 198, 0.1) 0%, transparent 50%),
                radial-gradient(circle at 80% 80%, rgba(255, 119, 198, 0.1) 0%, transparent 50%),
                radial-gradient(circle at 40% 20%, rgba(119, 198, 120, 0.1) 0%, transparent 50%);
            z-index: -1;
            animation: floatBackground 20s ease-in-out infinite;
        }
        
        @keyframes floatBackground {
            0%, 100% { transform: translate(0, 0) rotate(0deg); }
            33% { transform: translate(-20px, -20px) rotate(1deg); }
            66% { transform: translate(20px, -10px) rotate(-1deg); }
        }
        
        header {
            background: rgba(255, 255, 255, 0.95);
            backdrop-filter: blur(10px);
            box-shadow: 0 2px 20px rgba(0, 0, 0, 0.1);
            padding: 20px 40px;
            position: sticky;
            top: 0;
            z-index: 100;
        }
        
        header nav {
            max-width: 1200px;
            margin: 0 auto;
            display: flex;
            justify-content: space-between;
            align-items: center;
        }
        
        .logo {
            font-size: 28px;
            font-weight: bold;
            cursor: pointer;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            display: flex;
            align-items: center;
            gap: 8px;
        }
        
        nav button {
            background: white;
            border: 2px solid #e0e0e0;
            color: #5a5a5a;
            padding: 10px 20px;
            margin: 0 5px;
            border-radius: 25px;
            cursor: pointer;
            font-size: 14px;
            font-weight: 500;
        }
        
        nav button:hover {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            border-color: transparent;
            transform: translateY(-2px);
            box-shadow: 0 5px 15px rgba(102, 126, 234, 0.3);
        }
        
        .user-badge {
            display: inline-flex;
            align-items: center;
            gap: 10px;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            padding: 8px 16px;
            border-radius: 20px;
            font-size: 14px;
            cursor: pointer;
        }
        
        .container {
            max-width: 1200px;
            margin: 0 auto;
            padding: 40px 20px;
        }
        
        .hidden {
            display: none !important;
        }
        
        .page {
            animation: fadeIn 0.5s ease;
        }
        
        @keyframes fadeIn {
            from { opacity: 0; transform: translateY(20px); }
            to { opacity: 1; transform: translateY(0); }
        }
        
        .hero {
            text-align: center;
            margin-bottom: 60px;
            padding: 60px 20px;
            background: rgba(255, 255, 255, 0.8);
            border-radius: 30px;
            box-shadow: 0 10px 40px rgba(0, 0, 0, 0.1);
        }
        
        .hero h1 {
            font-size: 48px;
            margin-bottom: 20px;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
        }
        
        .hero p {
            font-size: 18px;
            margin-bottom: 30px;
            color: #666;
        }
        
        .btn-primary {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            border: none;
            color: white;
            padding: 15px 40px;
            font-size: 16px;
            border-radius: 30px;
            cursor: pointer;
            font-weight: bold;
            box-shadow: 0 4px 15px rgba(102, 126, 234, 0.3);
        }
        
        .btn-primary:hover {
            transform: translateY(-3px);
            box-shadow: 0 6px 25px rgba(102, 126, 234, 0.4);
        }
        
        .btn-primary:disabled {
            opacity: 0.6;
            cursor: not-allowed;
        }
        
        .grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
            gap: 30px;
            margin-top: 40px;
        }
        
        .card {
            background: white;
            border-radius: 20px;
            padding: 30px;
            text-align: center;
            cursor: pointer;
            box-shadow: 0 5px 20px rgba(0, 0, 0, 0.08);
            transition: all 0.3s ease;
        }
        
        .card:hover {
            transform: translateY(-5px);
            box-shadow: 0 10px 35px rgba(0, 0, 0, 0.15);
        }
        
        .card-icon {
            font-size: 50px;
            margin-bottom: 20px;
            display: inline-block;
            width: 80px;
            height: 80px;
            line-height: 80px;
            background: linear-gradient(135deg, #E3F2FD 0%, #F3E5F5 100%);
            border-radius: 20px;
        }
        
        .card h3 {
            font-size: 22px;
            margin-bottom: 10px;
            color: #2c3e50;
        }
        
        .card p {
            color: #666;
            font-size: 14px;
            line-height: 1.6;
        }
        
        .card button {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            border: none;
            color: white;
            padding: 12px 30px;
            border-radius: 25px;
            cursor: pointer;
            margin-top: 20px;
            font-weight: 600;
            width: 100%;
        }
        
        .card button:hover {
            transform: scale(1.05);
            box-shadow: 0 5px 15px rgba(102, 126, 234, 0.3);
        }
        
        .lesson-list {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
            gap: 20px;
            margin: 30px 0;
        }
        
        .lesson-item {
            background: white;
            border: 2px solid #e0e0e0;
            border-radius: 15px;
            padding: 20px;
            cursor: pointer;
            transition: all 0.3s ease;
        }
        
        .lesson-item:hover {
            border-color: #667eea;
            transform: translateY(-3px);
            box-shadow: 0 5px 20px rgba(102, 126, 234, 0.2);
        }
        
        .lesson-item.complete {
            border-color: #4CAF50;
            background: linear-gradient(135deg, #E8F5E9 0%, #F1F8E9 100%);
        }
        
        .lesson-item.complete::after {
            content: "✓";
            float: right;
            color: #4CAF50;
            font-size: 24px;
            font-weight: bold;
        }
        
        .code-editor {
            background: white;
            border-radius: 15px;
            padding: 20px;
            margin: 20px 0;
            box-shadow: 0 5px 20px rgba(0, 0, 0, 0.08);
        }
        
        .code-editor textarea {
            width: 100%;
            height: 300px;
            background: #2d2d2d;
            color: #f8f8f2;
            border: none;
            border-radius: 10px;
            padding: 15px;
            font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
            font-size: 14px;
            resize: vertical;
            line-height: 1.6;
        }
        
        .code-editor textarea:focus {
            outline: none;
            box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.2);
        }
        
        .code-output {
            background: #f5f5f5;
            border: 2px solid #4CAF50;
            border-radius: 15px;
            padding: 20px;
            margin-top: 20px;
            font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
            color: #2c3e50;
            max-height: 300px;
            overflow-y: auto;
            white-space: pre-wrap;
        }
        
        .button-group {
            display: flex;
            gap: 15px;
            margin: 20px 0;
            flex-wrap: wrap;
        }
        
        .button-group button {
            padding: 12px 25px;
            border: none;
            border-radius: 25px;
            cursor: pointer;
            font-weight: 600;
            color: white;
            transition: all 0.3s ease;
        }
        
        .btn-run {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
        }
        
        .btn-complete {
            background: linear-gradient(135deg, #4CAF50 0%, #45a049 100%);
        }
        
        .btn-back {
            background: #9e9e9e;
        }
        
        .button-group button:hover {
            transform: translateY(-2px);
            box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
        }
        
        .quiz-question {
            background: white;
            border-radius: 15px;
            padding: 25px;
            margin: 20px 0;
            box-shadow: 0 3px 15px rgba(0, 0, 0, 0.08);
        }
        
        .quiz-question h4 {
            margin-bottom: 20px;
            font-size: 18px;
            color: #2c3e50;
        }
        
        .quiz-options {
            display: flex;
            flex-direction: column;
            gap: 12px;
        }
        
        .quiz-options label {
            background: #f8f9fa;
            border: 2px solid #e0e0e0;
            border-radius: 10px;
            padding: 15px;
            cursor: pointer;
            transition: all 0.3s ease;
        }
        
        .quiz-options label:hover {
            background: #e3f2fd;
            border-color: #667eea;
        }
        
        .quiz-options input {
            margin-right: 10px;
            cursor: pointer;
        }
        
        .form-group {
            margin: 20px 0;
        }
        
        .form-group label {
            display: block;
            margin-bottom: 8px;
            color: #666;
            font-weight: 500;
        }
        
        .form-group input, .form-group select {
            width: 100%;
            padding: 15px;
            border: 2px solid #e0e0e0;
            border-radius: 10px;
            font-size: 16px;
            background: white;
        }
        
        .form-group input:focus, .form-group select:focus {
            outline: none;
            border-color: #667eea;
            box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
        }
        
        .auth-container {
            max-width: 450px;
            margin: 50px auto;
            background: white;
            border-radius: 20px;
            padding: 40px;
            box-shadow: 0 10px 40px rgba(0, 0, 0, 0.1);
        }
        
        .auth-container h2 {
            color: #2c3e50;
            margin-bottom: 30px;
            text-align: center;
        }
        
        .auth-tabs {
            display: flex;
            gap: 10px;
            margin-bottom: 30px;
        }
        
        .auth-tab {
            flex: 1;
            padding: 10px;
            border: 2px solid #e0e0e0;
            background: white;
            border-radius: 10px;
            cursor: pointer;
            text-align: center;
            transition: all 0.3s ease;
        }
        
        .auth-tab.active {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            border-color: transparent;
        }
        
        .profile-section {
            background: white;
            border-radius: 20px;
            padding: 30px;
            margin-bottom: 30px;
            box-shadow: 0 5px 20px rgba(0, 0, 0, 0.08);
        }
        
        .profile-header {
            display: flex;
            align-items: center;
            gap: 20px;
            margin-bottom: 30px;
        }
        
        .profile-avatar {
            width: 80px;
            height: 80px;
            border-radius: 50%;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 36px;
            color: white;
            font-weight: bold;
        }
        
        .profile-info h3 {
            color: #2c3e50;
            margin-bottom: 5px;
        }
        
        .profile-info p {
            color: #666;
            font-size: 14px;
        }
        
        .stats-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
            gap: 20px;
            margin: 30px 0;
        }
        
        .stat-card {
            background: linear-gradient(135deg, #E3F2FD 0%, #F3E5F5 100%);
            border-radius: 15px;
            padding: 20px;
            text-align: center;
        }
        
        .stat-card .value {
            font-size: 32px;
            font-weight: bold;
            color: #667eea;
        }
        
        .stat-card .label {
            color: #666;
            font-size: 14px;
            margin-top: 5px;
        }
        
        .dashboard-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
            gap: 30px;
            margin: 30px 0;
        }
        
        .dashboard-card {
            background: white;
            border-radius: 20px;
            padding: 30px;
            box-shadow: 0 5px 20px rgba(0, 0, 0, 0.08);
        }
        
        .dashboard-card h3 {
            font-size: 22px;
            margin-bottom: 20px;
            color: #2c3e50;
        }
        
        .score-item {
            background: #f8f9fa;
            border-radius: 10px;
            padding: 15px;
            margin: 10px 0;
            display: flex;
            justify-content: space-between;
            align-items: center;
            border-left: 4px solid #667eea;
        }
        
        .score-bar {
            height: 8px;
            background: #e0e0e0;
            border-radius: 5px;
            margin-top: 10px;
            overflow: hidden;
        }
        
        .score-fill {
            height: 100%;
            background: linear-gradient(90deg, #4CAF50 0%, #45a049 100%);
        }
        
        .score-bad { background: linear-gradient(90deg, #f44336 0%, #da190b 100%) !important; }
        .score-ok { background: linear-gradient(90deg, #ff9800 0%, #e68900 100%) !important; }
        .score-good { background: linear-gradient(90deg, #4CAF50 0%, #45a049 100%) !important; }
        
        .achievements {
            display: grid;
            grid-template-columns: repeat(6, 1fr);
            gap: 15px;
            margin-top: 20px;
        }
        
        .achievement {
            background: linear-gradient(135deg, #E3F2FD 0%, #F3E5F5 100%);
            border-radius: 15px;
            padding: 20px;
            text-align: center;
            cursor: pointer;
            transition: all 0.3s ease;
        }
        
        .achievement:hover {
            transform: scale(1.1);
            box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
        }
        
        .achievement-emoji {
            font-size: 40px;
            margin-bottom: 10px;
        }
        
        .pricing-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
            gap: 30px;
            margin: 40px 0;
        }
        
        .pricing-card {
            background: white;
            border-radius: 20px;
            padding: 40px;
            text-align: center;
            transition: all 0.3s ease;
            box-shadow: 0 5px 20px rgba(0, 0, 0, 0.08);
        }
        
        .pricing-card:hover {
            transform: translateY(-10px);
            box-shadow: 0 15px 40px rgba(0, 0, 0, 0.15);
        }
        
        .pricing-card.popular {
            border: 3px solid #667eea;
            transform: scale(1.05);
        }
        
        .pricing-card h3 {
            font-size: 24px;
            margin-bottom: 15px;
            color: #2c3e50;
        }
        
        .price {
            font-size: 48px;
            font-weight: bold;
            margin: 20px 0;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
        }
        
        .features {
            text-align: left;
            margin: 30px 0;
        }
        
        .features li {
            list-style: none;
            padding: 10px 0;
            border-bottom: 1px solid #e0e0e0;
            color: #666;
        }
        
        .features li:before {
            content: "✓ ";
            color: #4CAF50;
            font-weight: bold;
            margin-right: 10px;
        }
        
        footer {
            background: white;
            border-top: 1px solid #e0e0e0;
            padding: 30px;
            text-align: center;
            margin-top: 60px;
            color: #666;
        }
        
        .language-selector {
            margin: 10px 0;
            padding: 15px;
            background: #f8f9fa;
            border-radius: 10px;
            display: inline-block;
        }
        
        .language-selector select {
            padding: 8px 15px;
            border-radius: 5px;
            background: white;
            color: #2c3e50;
            border: 2px solid #e0e0e0;
            font-size: 14px;
            cursor: pointer;
        }
        
        .language-selector select:focus {
            outline: none;
            border-color: #667eea;
        }

        .loading {
            text-align: center;
            padding: 50px;
            color: #666;
        }

        .loading::after {
            content: "...";
            animation: dots 1.5s steps(4, end) infinite;
        }

        @keyframes dots {
            0%, 20% { content: ""; }
            40% { content: "."; }
            60% { content: ".."; }
            80%, 100% { content: "..."; }
        }

        /* Success messages */
        .success-message {
            background: #E8F5E9;
            color: #2E7D32;
            padding: 15px;
            border-radius: 10px;
            margin: 20px 0;
            border-left: 4px solid #4CAF50;
        }

        /* Error messages */
        .error-message {
            background: #FFEBEE;
            color: #C62828;
            padding: 15px;
            border-radius: 10px;
            margin: 20px 0;
            border-left: 4px solid #f44336;
        }
        
        .link-text {
            color: #667eea;
            cursor: pointer;
            text-decoration: underline;
        }
        
        .link-text:hover {
            color: #764ba2;
        }