.sig-digit {
            display: inline-block;
            padding: 0.1rem 0.2rem;
            border-radius: 3px;
            font-family: 'Courier New', monospace;
            font-size: 2rem;
            font-weight: 600;
            transition: all 0.2s;
            margin: 0 1px;
        }
        .sig-digit.valid {
            background-color: rgba(40, 167, 69, 0.25);
            color: #155724;
            border-bottom: 3px solid #28a745;
        }
        .sig-digit.invalid {
            background-color: rgba(220, 53, 69, 0.15);
            color: #721c24;
            border-bottom: 3px solid #dc3545;
            opacity: 0.6;
        }
        .sig-digit.placeholder {
            color: #adb5bd;
            font-weight: 300;
        }
        .sig-display {
            background-color: #f8f9fa;
            border-radius: 8px;
            padding: 1.2rem 1.5rem;
            text-align: center;
            border: 1px solid #dee2e6;
            min-height: 80px;
            display: flex;
            align-items: center;
            justify-content: center;
            flex-wrap: wrap;
            gap: 0.1rem;
        }
        .sig-result-box {
            background-color: white;
            border-radius: 8px;
            padding: 1rem 1.5rem;
            border: 1px solid #e9ecef;
            box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
        }
        .sig-rule-card {
            background-color: #f8f9fa;
            border-left: 4px solid var(--primary-color);
            padding: 1rem 1.2rem;
            margin-bottom: 1rem;
            border-radius: 0 6px 6px 0;
            transition: background 0.2s;
        }
        .sig-rule-card:hover {
            background-color: #eef4fa;
        }
        .sig-rule-card .rule-number {
            display: inline-block;
            background: var(--primary-color);
            color: white;
            border-radius: 50%;
            width: 28px;
            height: 28px;
            text-align: center;
            line-height: 28px;
            font-weight: 700;
            font-size: 0.85rem;
            margin-right: 10px;
        }
        .sig-mode-tab {
            cursor: pointer;
            padding: 0.5rem 1.2rem;
            border-radius: 30px;
            background: #f1f3f5;
            border: 2px solid transparent;
            transition: all 0.25s;
            font-weight: 500;
        }
        .sig-mode-tab.active {
            background: var(--primary-color);
            color: white;
            border-color: var(--primary-color);
        }
        .sig-mode-tab:hover:not(.active) {
            background: #e9ecef;
            border-color: #ced4da;
        }
        .sig-example-btn {
            background: rgba(70, 130, 180, 0.08);
            border: 1px solid rgba(70, 130, 180, 0.2);
            border-radius: 20px;
            padding: 0.3rem 1rem;
            font-size: 0.85rem;
            color: var(--primary-color);
            cursor: pointer;
            transition: all 0.2s;
            font-family: 'Courier New', monospace;
        }
        .sig-example-btn:hover {
            background: rgba(70, 130, 180, 0.18);
            transform: translateY(-2px);
            box-shadow: 0 2px 8px rgba(0, 0, 0, 0.06);
        }
        .sig-operator-btn {
            width: 48px;
            height: 48px;
            border-radius: 50%;
            border: 2px solid #dee2e6;
            background: white;
            font-size: 1.4rem;
            font-weight: 700;
            transition: all 0.2s;
            display: inline-flex;
            align-items: center;
            justify-content: center;
        }
        .sig-operator-btn.active {
            border-color: var(--primary-color);
            background: var(--primary-color);
            color: white;
        }
        .sig-operator-btn:hover {
            border-color: var(--primary-color);
            background: rgba(70, 130, 180, 0.08);
        }
        .sig-operator-btn.active:hover {
            background: var(--primary-color);
            color: white;
        }
        .sig-property-table {
            width: 100%;
            border-collapse: collapse;
            margin: 1.5rem 0;
        }
        .sig-property-table th,
        .sig-property-table td {
            padding: 0.75rem 1rem;
            border: 1px solid var(--border-color);
            text-align: left;
        }
        .sig-property-table th {
            background-color: var(--light-gray);
            font-weight: 600;
        }
        .sig-property-table tr:nth-child(even) {
            background-color: rgba(70, 130, 180, 0.04);
        }
        .sig-property-table .example-cell {
            font-family: 'Courier New', monospace;
            font-size: 0.95rem;
        }
        .sig-badge {
            display: inline-block;
            background: var(--primary-color);
            color: white;
            padding: 0.2rem 0.8rem;
            border-radius: 20px;
            font-size: 0.85rem;
            font-weight: 600;
        }
        .sig-case-study {
            background: linear-gradient(135deg, #f0f7fa 0%, #e8f0f5 100%);
            border-radius: 10px;
            padding: 1.5rem 2rem;
            margin: 1.5rem 0;
            border-left: 5px solid var(--primary-color);
        }
        .sig-authority-note {
            font-size: 0.85rem;
            color: var(--text-muted);
            border-top: 1px solid var(--border-color);
            padding-top: 1rem;
            margin-top: 1rem;
            text-align: right;
        }
        .sig-deep-dive {
            margin: 1.8rem 0;
        }
        .sig-deep-dive p {
            text-align: justify;
        }
        .sig-key-point {
            font-weight: 500;
            color: var(--accent-color);
        }
        .sig-privacy-note {
            font-size: 0.9rem;
            background-color: #e7f3ff;
            border: 1px solid #b8daff;
            color: #004085;
            padding: 0.5rem 1rem;
            border-radius: 4px;
            margin: 1rem 0;
        }
        .sig-warning {
            background-color: #fff3cd;
            border: 1px solid #ffeeba;
            color: #856404;
            padding: 0.5rem 1rem;
            border-radius: 4px;
            margin: 1rem 0;
            display: none;
        }
        .sig-result-value {
            font-size: 2.2rem;
            font-weight: 700;
            color: var(--primary-color);
            font-family: 'Courier New', monospace;
        }
        .sig-unit-note {
            font-size: 0.9rem;
            color: #6c757d;
        }
        .sig-legend {
            display: flex;
            justify-content: center;
            gap: 1.5rem;
            margin: 0.5rem 0 1rem;
            font-size: 0.9rem;
        }
        .sig-legend-item {
            display: flex;
            align-items: center;
            gap: 0.4rem;
        }
        .sig-legend-color {
            width: 18px;
            height: 18px;
            border-radius: 4px;
        }
        .sig-legend-color.green {
            background-color: rgba(40, 167, 69, 0.4);
            border: 2px solid #28a745;
        }
        .sig-legend-color.red {
            background-color: rgba(220, 53, 69, 0.3);
            border: 2px solid #dc3545;
        }
        .sig-operator-group {
            display: flex;
            gap: 0.5rem;
            justify-content: center;
            margin: 0.5rem 0;
        }
        .sig-calc-mode {
            display: none;
        }
        .sig-calc-mode.active {
            display: block;
        }
        .sig-result-detail {
            background: #f8f9fa;
            border-radius: 6px;
            padding: 0.8rem 1.2rem;
            margin: 0.5rem 0;
            font-family: 'Courier New', monospace;
        }
        @media (max-width: 768px) {
            .sig-digit {
                font-size: 1.5rem;
                padding: 0.05rem 0.15rem;
            }
            .sig-display {
                padding: 0.8rem 1rem;
                min-height: 60px;
            }
            .sig-result-value {
                font-size: 1.6rem;
            }
            .sig-operator-btn {
                width: 40px;
                height: 40px;
                font-size: 1.1rem;
            }
        }