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

        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            background-color: #f4f6f9;
            padding: 20px;
            line-height: 1.6;
        }

        .container {
            max-width: 700px;
            margin: 0 auto;
            background: white;
            border-radius: 12px;
            box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
            overflow: hidden;
        }

        .header {
            background: linear-gradient(135deg, #4a90e2, #357abd);
            color: white;
            padding: 25px;
            text-align: center;
        }

        .header h1 {
            font-size: 1.8rem;
            margin-bottom: 8px;
        }

        .header p {
            opacity: 0.9;
            font-size: 1rem;
        }

        /* Tree Container */
        .tree {
            padding: 0;
        }

        /* Category Styles */
        .category {
            border-bottom: 1px solid #e9ecef;
        }

        .category:last-child {
            border-bottom: none;
        }

        .category-header {
            background: #f8f9fa;
            padding: 18px 25px;
            cursor: pointer;
            display: flex;
            align-items: center;
            justify-content: space-between;
            transition: all 0.3s ease;
            border: none;
            width: 100%;
            text-align: left;
            font-size: 1.1rem;
            font-weight: 600;
            color: #2c3e50;
            user-select: none;
        }

        .category-header:hover {
            background: #e9ecef;
        }

        .category-header.active {
            background: #4a90e2;
            color: white;
        }

        .category-icon {
            transition: transform 0.3s ease;
            font-size: 0.9rem;
            opacity: 0.7;
        }

        .category-header.active .category-icon {
            transform: rotate(90deg);
        }

        /* Subtypes Container */
        .subtypes {
            max-height: 0;
            overflow: hidden;
            transition: max-height 0.4s ease;
            background: white;
        }

        .subtypes.open {
            max-height: 1000px;
        }

        /* Subtype Styles */
        .subtype {
            border-bottom: 1px solid #f1f3f5;
        }

        .subtype:last-child {
            border-bottom: none;
        }

        .subtype-header {
            padding: 15px 25px 15px 45px;
            cursor: pointer;
            display: flex;
            align-items: center;
            justify-content: space-between;
            transition: all 0.3s ease;
            background: white;
            color: #495057;
            font-size: 1rem;
            user-select: none;
        }

        .subtype-header:hover {
            background: #f8f9fa;
            padding-left: 50px;
        }

        .subtype-header.active {
            background: #e3f2fd;
            color: #1976d2;
            font-weight: 500;
        }

        .subtype-icon {
            font-size: 0.8rem;
            opacity: 0.6;
            transition: all 0.3s ease;
        }

        .subtype-header.active .subtype-icon {
            transform: rotate(90deg);
            opacity: 1;
        }

        /* Description Styles */
        .description {
            max-height: 0;
            overflow: hidden;
            transition: all 0.3s ease;
            background: #f8f9fb;
        }

        .description.open {
            max-height: 300px;
            padding: 20px 25px 20px 65px;
        }

        .description p {
            color: #6c757d;
            font-size: 0.95rem;
            line-height: 1.6;
            margin: 0;
        }

        /* Mobile Responsive */
        @media (max-width: 768px) {
            body {
                padding: 10px;
            }

            .header {
                padding: 20px 15px;
            }

            .header h1 {
                font-size: 1.5rem;
            }

            .category-header {
                padding: 15px 20px;
                font-size: 1rem;
            }

            .subtype-header {
                padding: 12px 20px 12px 35px;
                font-size: 0.9rem;
            }

            .subtype-header:hover {
                padding-left: 40px;
            }

            .description.open {
                padding: 15px 20px 15px 45px;
            }

            .description p {
                font-size: 0.9rem;
            }
        }

        /* Animation */
        .fade-in {
            animation: fadeIn 0.3s ease;
        }

        @keyframes fadeIn {
            from {
                opacity: 0;
                transform: translateY(-5px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }