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

        body {
            font-family: 'Ubuntu', 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            background: linear-gradient(135deg, #0a192f 0%, #1a2332 100%);
            color: #e6f1ff;
            min-height: 100vh;
            padding: 0;
        }

        .navbar {
            background: rgba(15, 23, 42, 0.95);
            border-bottom: 2px solid rgba(100, 255, 218, 0.3);
            padding: 15px 0;
            position: sticky;
            top: 0;
            z-index: 1000;
            backdrop-filter: blur(10px);
        }

        .nav-container {
            max-width: 1200px;
            margin: 0 auto;
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 0 20px;
        }

        .nav-logo {
            font-size: 1.5em;
            font-weight: bold;
            color: #64ffda;
            text-shadow: 0 0 10px rgba(100, 255, 218, 0.5);
        }

        .nav-menu {
            display: flex;
            gap: 30px;
            list-style: none;
        }

        .nav-item {
            position: relative;
        }

        .nav-link {
            color: #ccd6f6;
            text-decoration: none;
            font-weight: 500;
            padding: 8px 16px;
            border-radius: 6px;
            transition: all 0.3s ease;
            cursor: pointer;
        }

        .nav-link:hover {
            color: #64ffda;
            background: rgba(100, 255, 218, 0.1);
        }

        .nav-link.active {
            color: #64ffda;
            background: rgba(100, 255, 218, 0.15);
        }

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

        .section {
            display: none;
        }

        .section.active {
            display: block;
        }

        .header {
            text-align: center;
            margin-bottom: 40px;
            padding: 30px;
            background: rgba(30, 41, 59, 0.6);
            border-radius: 12px;
            border: 1px solid rgba(100, 255, 218, 0.2);
        }

        .header h1 {
            font-size: 3em;
            color: #64ffda;
            margin-bottom: 10px;
            text-shadow: 0 0 20px rgba(100, 255, 218, 0.5);
        }

        .header p {
            color: #8892b0;
            font-size: 1.1em;
        }

        .stats {
            display: flex;
            gap: 20px;
            justify-content: center;
            margin-top: 20px;
        }

        .stat-box {
            background: rgba(100, 255, 218, 0.1);
            padding: 15px 30px;
            border-radius: 8px;
            border: 1px solid rgba(100, 255, 218, 0.3);
        }

        .stat-box .label {
            color: #8892b0;
            font-size: 0.9em;
        }

        .stat-box .value {
            color: #64ffda;
            font-size: 1.5em;
            font-weight: bold;
        }

        .player-name {
            color: #64ffda;
            font-size: 0.9em;
            margin-top: 5px;
        }

        .completed-badge {
            display: inline-block;
            background: rgba(34, 197, 94, 0.2);
            color: #22c55e;
            padding: 4px 12px;
            border-radius: 12px;
            font-size: 0.85em;
            font-weight: 600;
            margin-left: 10px;
        }

        .level-card {
            background: rgba(30, 41, 59, 0.8);
            border: 1px solid rgba(100, 255, 218, 0.2);
            border-radius: 8px;
            margin-bottom: 20px;
            overflow: hidden;
            transition: all 0.3s ease;
        }

        .level-card:hover {
            border-color: rgba(100, 255, 218, 0.5);
            box-shadow: 0 5px 20px rgba(100, 255, 218, 0.1);
        }

        .level-header {
            padding: 20px;
            display: flex;
            align-items: center;
            justify-content: space-between;
            cursor: pointer;
            background: rgba(15, 23, 42, 0.5);
        }

        .level-header:hover {
            background: rgba(15, 23, 42, 0.7);
        }

        .level-info {
            display: flex;
            align-items: center;
            gap: 15px;
            flex: 1;
        }

        .level-number {
            width: 50px;
            height: 50px;
            background: rgba(100, 255, 218, 0.2);
            border: 2px solid #64ffda;
            border-radius: 8px;
            display: flex;
            align-items: center;
            justify-content: center;
            font-weight: bold;
            font-size: 1.2em;
            color: #64ffda;
        }

        .level-number.completed {
            background: rgba(34, 197, 94, 0.3);
            border-color: #22c55e;
            color: #22c55e;
        }

        .level-details h3 {
            color: #e6f1ff;
            margin-bottom: 5px;
        }

        .level-meta {
            display: flex;
            gap: 15px;
            align-items: center;
        }

        .badge {
            padding: 4px 12px;
            border-radius: 12px;
            font-size: 0.85em;
            font-weight: 600;
        }

        .badge.easy { background: rgba(34, 197, 94, 0.2); color: #22c55e; }
        .badge.medium { background: rgba(234, 179, 8, 0.2); color: #eab308; }
        .badge.hard { background: rgba(249, 115, 22, 0.2); color: #f97316; }

        .points {
            color: #64ffda;
            font-weight: bold;
        }

        .expand-icon {
            color: #64ffda;
            transition: transform 0.3s ease;
        }

        .expand-icon.rotated {
            transform: rotate(180deg);
        }

        .level-content {
            max-height: 0;
            overflow: hidden;
            transition: max-height 0.3s ease;
        }

        .level-content.expanded {
            max-height: 2000px;
        }

        .level-body {
            padding: 25px;
            border-top: 1px solid rgba(100, 255, 218, 0.1);
        }

        .description {
            color: #ccd6f6;
            line-height: 1.6;
            margin-bottom: 20px;
        }

        .answer-section {
            margin-top: 20px;
        }

        .input-group {
            display: flex;
            gap: 10px;
            margin-bottom: 15px;
        }

        input[type="text"], input[type="password"] {
            flex: 1;
            padding: 12px 15px;
            background: rgba(15, 23, 42, 0.8);
            border: 1px solid rgba(100, 255, 218, 0.3);
            border-radius: 6px;
            color: #e6f1ff;
            font-size: 1em;
            transition: all 0.3s ease;
        }

        input[type="text"]:focus, input[type="password"]:focus {
            outline: none;
            border-color: #64ffda;
            box-shadow: 0 0 0 3px rgba(100, 255, 218, 0.1);
        }

        .btn {
            padding: 12px 24px;
            border: none;
            border-radius: 6px;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s ease;
            font-size: 1em;
        }

        .btn-submit {
            background: #64ffda;
            color: #0a192f;
        }

        .btn-submit:hover {
            background: #52d4ba;
            transform: translateY(-2px);
            box-shadow: 0 5px 15px rgba(100, 255, 218, 0.3);
        }

        .btn-submit:disabled {
            opacity: 0.6;
            cursor: not-allowed;
        }

        .feedback {
            padding: 12px 15px;
            border-radius: 6px;
            margin-top: 10px;
            display: none;
            align-items: center;
            gap: 10px;
        }

        .feedback.show {
            display: flex;
        }

        .feedback.success {
            background: rgba(34, 197, 94, 0.2);
            border: 1px solid #22c55e;
            color: #22c55e;
        }

        .feedback.error {
            background: rgba(239, 68, 68, 0.2);
            border: 1px solid #ef4444;
            color: #ef4444;
        }

        .login-box {
            background: rgba(15, 23, 42, 0.8);
            border: 1px solid rgba(100, 255, 218, 0.3);
            border-radius: 8px;
            padding: 25px;
            margin: 20px 0;
        }

        .login-box h4 {
            color: #64ffda;
            margin-bottom: 15px;
        }

        .login-box label {
            display: block;
            color: #8892b0;
            margin-bottom: 8px;
            margin-top: 15px;
        }

        .sql-hint {
            background: rgba(100, 255, 218, 0.05);
            border-left: 3px solid #64ffda;
            padding: 15px;
            margin: 15px 0;
            border-radius: 4px;
            color: #ccd6f6;
        }

        @keyframes slideIn {
            from {
                opacity: 0;
                transform: translateY(-10px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }

        .level-card {
            animation: slideIn 0.5s ease forwards;
        }

        @media (max-width: 768px) {
            .header h1 {
                font-size: 2em;
            }

            .stats {
                flex-direction: column;
            }

            .level-info {
                flex-direction: column;
                align-items: flex-start;
            }

            .input-group {
                flex-direction: column;
            }

            .nav-menu {
                gap: 15px;
            }

            .nav-link {
                padding: 6px 12px;
                font-size: 0.9em;
            }
        }

        .about-content {
            background: rgba(30, 41, 59, 0.6);
            border: 1px solid rgba(100, 255, 218, 0.2);
            border-radius: 12px;
            padding: 40px;
            line-height: 1.8;
        }

        .about-content h2 {
            color: #64ffda;
            margin-bottom: 20px;
            font-size: 2em;
        }

        .about-content h3 {
            color: #64ffda;
            margin-top: 30px;
            margin-bottom: 15px;
            font-size: 1.5em;
        }

        .about-content p {
            color: #ccd6f6;
            margin-bottom: 15px;
        }

        .completion-modal {
            display: none;
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background: rgba(0, 0, 0, 0.8);
            z-index: 2000;
            justify-content: center;
            align-items: center;
        }

        .completion-modal.show {
            display: flex;
        }

        .modal-content {
            background: rgba(30, 41, 59, 0.95);
            border: 2px solid #64ffda;
            border-radius: 12px;
            padding: 40px;
            max-width: 500px;
            width: 90%;
            text-align: center;
            animation: modalSlideIn 0.5s ease;
        }

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

        .modal-content h2 {
            color: #64ffda;
            font-size: 2em;
            margin-bottom: 20px;
        }

        .modal-content p {
            color: #ccd6f6;
            margin-bottom: 30px;
            font-size: 1.1em;
        }

        .modal-content input[type="text"] {
            width: 100%;
            padding: 15px;
            margin-bottom: 20px;
            background: rgba(15, 23, 42, 0.8);
            border: 1px solid rgba(100, 255, 218, 0.3);
            border-radius: 6px;
            color: #e6f1ff;
            font-size: 1.1em;
        }

        .trophy-icon {
            font-size: 3em;
            margin-bottom: 20px;
        }