.input-group-custom {
            margin-bottom: 1rem;
        }
        .deep-dive {
            margin: 1.8rem 0;
        }
        .deep-dive p {
            text-align: justify;
        }
        .unit-note {
            font-size: 0.9rem;
            color: #6c757d;
        }
        .coord-input {
            margin-bottom: 0.5rem;
        }
        .result-text {
            font-family: 'Courier New', monospace;
            font-size: 1.4rem;
            padding: 1.5rem;
            background-color: #f8f9fa;
            border-radius: 8px;
            border: 1px solid #ddd;
            min-height: 80px;
            word-break: break-all;
            white-space: pre-wrap;
        }
        .result-label {
            font-weight: 600;
            margin-top: 1rem;
            margin-bottom: 0.5rem;
        }
        .character-count {
            font-size: 0.9rem;
            color: #6c757d;
            text-align: right;
            margin-top: 0.25rem;
        }
        .rot13-badge {
            display: inline-block;
            background-color: #2d3748;
            color: #fff;
            padding: 0.2rem 0.8rem;
            border-radius: 20px;
            font-size: 0.8rem;
            font-weight: 600;
            letter-spacing: 0.5px;
        }
        .alphabet-ring {
            display: flex;
            flex-wrap: wrap;
            justify-content: center;
            gap: 0.15rem;
            margin: 1.5rem 0;
            font-family: 'Courier New', monospace;
            font-size: 1.1rem;
        }
        .alphabet-ring .letter {
            background-color: #f1f3f5;
            padding: 0.25rem 0.4rem;
            border-radius: 4px;
            border: 1px solid #dee2e6;
            min-width: 2rem;
            text-align: center;
        }
        .alphabet-ring .letter.rot {
            background-color: #d4edda;
            border-color: #28a745;
        }
        .alphabet-ring .letter.original {
            background-color: #cce5ff;
            border-color: #0d6efd;
        }
        .alphabet-ring .arrow {
            padding: 0.25rem 0.2rem;
            color: #6c757d;
        }
        .alphabet-ring .label {
            font-size: 0.7rem;
            color: #6c757d;
            text-align: center;
            width: 100%;
            margin-top: 0.25rem;
        }
        .history-timeline {
            position: relative;
            padding-left: 2rem;
            margin: 1.5rem 0;
        }
        .history-timeline::before {
            content: '';
            position: absolute;
            left: 0.5rem;
            top: 0;
            bottom: 0;
            width: 2px;
            background: var(--primary-color);
        }
        .history-event {
            position: relative;
            margin-bottom: 1.5rem;
            padding-left: 1rem;
        }
        .history-event::before {
            content: '';
            position: absolute;
            left: -1.5rem;
            top: 0.4rem;
            width: 10px;
            height: 10px;
            background: var(--primary-color);
            border-radius: 50%;
            border: 2px solid #fff;
            box-shadow: 0 0 0 2px var(--primary-color);
        }
        .history-event .year {
            font-weight: 700;
            color: var(--primary-color);
        }
        .history-event .desc {
            color: #333;
        }
        .tool-header .rot13-icon {
            font-size: 2.5rem;
            color: var(--primary-color);
            margin-right: 0.75rem;
        }
        .quick-reference {
            background-color: #f8f9fa;
            border: 1px solid #dee2e6;
            border-radius: 8px;
            padding: 1rem;
            margin: 1.5rem 0;
        }
        .quick-reference code {
            font-size: 1rem;
            background: #fff;
            padding: 0.2rem 0.4rem;
            border-radius: 3px;
        }
        .dual-input-area {
            display: flex;
            flex-direction: column;
            gap: 1.5rem;
        }
        @media (min-width: 768px) {
            .dual-input-area {
                flex-direction: row;
                gap: 2rem;
            }
            .dual-input-area > div {
                flex: 1;
            }
        }
        :root {
            --bg-body: #f8f9fa;
            --text-color: #212529;
            --card-bg: #ffffff;
            --border-color: #dee2e6;
            --light-gray: #f1f3f5;
            --text-muted: #6c757d;
     
            --input-bg: #ffffff;
            --input-border: #ced4da;
            --result-bg: #f8f9fa;
            --result-border: #ddd;
            --shadow-color: rgba(0,0,0,0.1);
        }
        [data-theme="dark"] {
            --bg-body: #1a1d20;
            --text-color: #e9ecef;
            --card-bg: #2b3035;
            --border-color: #495057;
            --light-gray: #343a40;
            --text-muted: #adb5bd;
            --primary-color: #6ea8fe;
            --accent-color: #6ea8fe;
            --input-bg: #343a40;
            --input-border: #495057;
            --result-bg: #343a40;
            --result-border: #495057;
            --shadow-color: rgba(0,0,0,0.5);
        }
        .tool-card, .math-box, .case-study, .author-bio, .quick-reference,
        .property-table th, .property-table td, .alphabet-ring .letter,
        .history-event .desc, .result-text, .privacy-note, .result-text {
            background-color: var(--result-bg);
            border-color: var(--result-border);
        }
        .alphabet-ring .letter.original {
            background-color: #cce5ff;
            border-color: #0d6efd;
        }
        [data-theme="dark"] .alphabet-ring .letter.original {
            background-color: #2c3e50;
            border-color: #6ea8fe;
        }
        .alphabet-ring .letter.rot {
            background-color: #d4edda;
            border-color: #28a745;
        }
        [data-theme="dark"] .alphabet-ring .letter.rot {
            background-color: #2c4e3a;
            border-color: #5cb85c;
        }
        [data-theme="dark"] [data-theme="dark"] [data-theme="dark"] [data-theme="dark"] .navbar, .theme-toggle {
            cursor: pointer;
            background: transparent;
            border: none;
            font-size: 1.2rem;
            color: var(--text-color);
            transition: 0.3s;
        }
        .theme-toggle:hover {
            transform: scale(1.1);
        }
        .tool-header h1 {
            flex: 1;
        }
        .theme-toggle-wrapper {
            margin-left: 1rem;
        }
        .form-switch .form-check-input {
            width: 2.5em;
            height: 1.25em;
        }
        .cipher-selector {
            max-width: 200px;
        }
        .btn-group-options {
            gap: 0.5rem;
        }