/* === A4 Print Layout === */
        @page {
            size: A4;
            margin: 20mm 18mm 25mm 18mm;
        }

        @media print {
            body { padding: 0; margin: 0; max-width: 170mm; }
            .no-print { display: none !important; }
            .page-break { page-break-before: always; }
            .avoid-break { page-break-inside: avoid; }
            a { color: inherit; text-decoration: none; }
            .toc a { color: #1a1a2e; }
        }

        /* === Base Styles === */
        * { box-sizing: border-box; margin: 0; padding: 0; }

        body {
            font-family: 'Inter', 'Segoe UI', system-ui, -apple-system, sans-serif;
            font-size: 11pt;
            line-height: 1.7;
            color: #1a1a2e;
            max-width: 960px;
            margin: 0 auto;
            padding: 40px 48px;
            background: white;
        }

        /* === Typography === */
        h1 {
            font-size: 22pt;
            font-weight: 700;
            color: #0f172a;
            margin-bottom: 8pt;
            line-height: 1.2;
        }

        h2 {
            font-size: 15pt;
            font-weight: 600;
            color: #1e293b;
            margin-top: 24pt;
            margin-bottom: 10pt;
            padding-bottom: 4pt;
            border-bottom: 2px solid #e2e8f0;
        }

        h3 {
            font-size: 12pt;
            font-weight: 600;
            color: #334155;
            margin-top: 16pt;
            margin-bottom: 8pt;
        }

        h4 {
            font-size: 10.5pt;
            font-weight: 600;
            color: #475569;
            margin-top: 12pt;
            margin-bottom: 6pt;
        }

        p { margin-bottom: 8pt; }

        /* === Title Page === */
        .title-page {
            text-align: center;
            padding: 60pt 0 40pt;
            min-height: 60vh;
            display: flex;
            flex-direction: column;
            justify-content: center;
            align-items: center;
        }

        .title-page .series-label {
            font-size: 10pt;
            font-weight: 500;
            text-transform: uppercase;
            letter-spacing: 2px;
            color: #1a9c8d;
            margin-bottom: 16pt;
        }

        .title-page h1 {
            font-size: 28pt;
            margin-bottom: 12pt;
        }

        .title-page .subtitle {
            font-size: 13pt;
            color: #64748b;
            font-weight: 400;
            max-width: 560px;
            margin-bottom: 40pt;
        }

        .title-page .meta {
            font-size: 9pt;
            color: #94a3b8;
        }

        /* === Table of Contents === */
        .toc {
            padding: 16pt 20pt;
            background: #f8fafc;
            border-radius: 8pt;
            margin: 20pt 0;
        }

        .toc h2 {
            font-size: 12pt;
            margin-top: 0;
            border: none;
            padding-bottom: 8pt;
        }

        .toc ol {
            list-style: none;
            counter-reset: toc;
            padding: 0;
        }

        .toc > ol > li {
            counter-increment: toc;
            margin-bottom: 4pt;
        }

        .toc > ol > li::before {
            content: counter(toc) ". ";
            font-weight: 600;
            color: #1a9c8d;
        }

        .toc a {
            color: #334155;
            text-decoration: none;
        }

        .toc a:hover { color: #1a9c8d; }

        .toc .sub-items {
            padding-left: 20pt;
            list-style: none;
        }

        .toc .sub-items li {
            font-size: 9.5pt;
            color: #64748b;
            margin-bottom: 2pt;
        }

        .toc .toc-part-label {
            font-weight: 600;
            font-size: 10pt;
            color: #1a9c8d;
            text-transform: uppercase;
            letter-spacing: 1px;
            margin-top: 12pt;
            margin-bottom: 4pt;
            padding-top: 8pt;
            border-top: 1px solid #e2e8f0;
        }

        .toc .toc-part-label:first-child {
            margin-top: 0;
            padding-top: 0;
            border-top: none;
        }

        /* === Part Dividers === */
        .part-divider {
            text-align: center;
            padding: 40pt 0 20pt;
        }

        .part-divider .part-label {
            font-size: 10pt;
            font-weight: 500;
            text-transform: uppercase;
            letter-spacing: 3px;
            color: #1a9c8d;
            margin-bottom: 8pt;
        }

        .part-divider h2 {
            border: none;
            font-size: 18pt;
            margin-top: 0;
        }

        .part-divider p {
            color: #64748b;
            font-size: 10.5pt;
        }

        /* === Info Boxes === */
        .info-box {
            background: #fafafa;
            border: 1px solid #e2e8f0;
            padding: 12pt 16pt;
            border-radius: 6pt;
            margin: 12pt 0;
            font-size: 10pt;
        }



        .info-box-title {
            font-weight: 600;
            margin-bottom: 4pt;
        }

        /* === Glossary / Definition Box === */
        .glossary {
            background: #fafafa;
            border: 1px solid #e2e8f0;
            border-radius: 8pt;
            padding: 16pt;
            margin: 16pt 0;
        }

        .glossary h3 {
            margin-top: 0;
            font-size: 11pt;
        }

        .glossary dl {
            margin: 0;
        }

        .glossary dt {
            font-weight: 600;
            color: #1e293b;
            margin-top: 8pt;
        }

        .glossary dd {
            margin-left: 0;
            padding-left: 16pt;
            color: #475569;
            font-size: 10pt;
        }

        /* === Figures === */
        figure {
            margin: 16pt 0;
            text-align: center;
            page-break-inside: avoid;
        }

        figure img {
            max-width: 100%;
            border: 1px solid #e2e8f0;
            border-radius: 6pt;
            box-shadow: 0 2px 8px rgba(0,0,0,0.08);
        }

        figcaption {
            font-size: 9pt;
            color: #64748b;
            font-style: italic;
            margin-top: 6pt;
        }

        /* === Tables === */
        table {
            width: 100%;
            border-collapse: collapse;
            margin: 12pt 0;
            font-size: 10pt;
            page-break-inside: avoid;
        }

        th, td {
            padding: 8pt 10pt;
            text-align: left;
            border-bottom: 1px solid #e2e8f0;
        }

        th {
            background: #f8fafc;
            font-weight: 600;
            color: #334155;
            font-size: 9.5pt;
            text-transform: uppercase;
            letter-spacing: 0.5px;
        }

        /* === Code / Formulas === */
        code {
            font-family: 'JetBrains Mono', monospace;
            font-size: 9pt;
            background: #f1f5f9;
            padding: 1pt 4pt;
            border-radius: 3pt;
            color: #0f172a;
        }

        pre {
            font-family: 'JetBrains Mono', monospace;
            font-size: 9pt;
            background: #f8fafc;
            border: 1px solid #e2e8f0;
            border-radius: 6pt;
            padding: 12pt 16pt;
            overflow-x: auto;
            margin: 10pt 0;
            line-height: 1.6;
        }

        .formula-box {
            background: #f8fafc;
            border: 1px solid #cbd5e1;
            border-radius: 8pt;
            padding: 16pt 20pt;
            margin: 14pt 0;
            text-align: center;
            page-break-inside: avoid;
        }

        .formula-box .formula {
            font-family: 'JetBrains Mono', monospace;
            font-size: 11pt;
            color: #1e293b;
            margin: 8pt 0;
        }

        .formula-box .formula-label {
            font-size: 9pt;
            color: #64748b;
            margin-top: 6pt;
        }

        /* === Example Walkthrough === */
        .example-box {
            background: #fefce8;
            border: 1px solid #fde68a;
            border-radius: 8pt;
            padding: 16pt;
            margin: 14pt 0;
            page-break-inside: avoid;
        }

        .example-box h4 {
            color: #92400e;
            margin-top: 0;
        }

        .example-box .calculation {
            font-family: 'JetBrains Mono', monospace;
            font-size: 9.5pt;
            background: white;
            border-radius: 4pt;
            padding: 10pt;
            margin: 8pt 0;
        }

        /* === UI Mockup Boxes === */
        .ui-box {
            background: #f8fafc;
            border: 2px solid #e2e8f0;
            border-radius: 10pt;
            padding: 20pt;
            margin: 14pt 0;
            page-break-inside: avoid;
        }

        .ui-box .ui-label {
            font-size: 9pt;
            text-transform: uppercase;
            letter-spacing: 1px;
            color: #94a3b8;
            font-weight: 600;
            margin-bottom: 6pt;
        }

        .ui-box .ui-field {
            display: flex;
            align-items: center;
            gap: 10pt;
            margin-bottom: 8pt;
        }

        .ui-box .ui-field-name {
            font-weight: 600;
            min-width: 120pt;
            color: #334155;
        }

        .ui-box .ui-field-value {
            background: white;
            border: 1px solid #cbd5e1;
            border-radius: 4pt;
            padding: 4pt 10pt;
            flex: 1;
            color: #475569;
            font-size: 10pt;
        }

        /* === Step-by-Step === */
        .step {
            display: flex;
            gap: 12pt;
            margin: 12pt 0;
            padding: 12pt;
            background: #fafafa;
            border-radius: 8pt;
            page-break-inside: avoid;
        }

        .step-number {
            flex-shrink: 0;
            width: 28pt;
            height: 28pt;
            background: #1a9c8d;
            color: white;
            font-weight: 700;
            font-size: 12pt;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .step-content {
            flex: 1;
        }

        .step-content p:last-child { margin-bottom: 0; }

        /* === Comparison Table (Method Summary) === */
        .method-comparison {
            border: 2px solid #e2e8f0;
            border-radius: 8pt;
            overflow: hidden;
            margin: 16pt 0;
        }

        .method-comparison th {
            background: #1e293b;
            color: white;
            text-transform: none;
            font-size: 10pt;
        }

        .method-comparison td {
            vertical-align: top;
        }

        .method-comparison .rank-best { color: #16a34a; font-weight: 600; }
        .method-comparison .rank-good { color: #2563eb; font-weight: 600; }
        .method-comparison .rank-ok { color: #d97706; font-weight: 600; }
        .method-comparison .rank-caution { color: #dc2626; font-weight: 600; }

        /* === References (APA 6) === */
        .references {
            margin-top: 30pt;
        }

        .references h2 {
            border-bottom: 2px solid #334155;
        }

        .references p {
            padding-left: 36pt;
            text-indent: -36pt;
            margin-bottom: 6pt;
            font-size: 9.5pt;
            line-height: 1.5;
        }

        /* === Utility === */
        .text-muted { color: #94a3b8; }
        .text-primary { color: #1a9c8d; }
        .font-mono { font-family: 'JetBrains Mono', monospace; }
        .mt-1 { margin-top: 8pt; }
        .mt-2 { margin-top: 16pt; }
        .mb-1 { margin-bottom: 8pt; }
        .mb-2 { margin-bottom: 16pt; }

        ul, ol { margin-bottom: 8pt; padding-left: 20pt; }
        li { margin-bottom: 4pt; }

        /* === Print Button (screen only) === */
        .print-btn {
            position: fixed;
            bottom: 20px;
            right: 20px;
            background: #1a9c8d;
            color: white;
            border: none;
            padding: 10px 20px;
            border-radius: 8px;
            cursor: pointer;
            font-size: 14px;
            box-shadow: 0 2px 10px rgba(0,0,0,0.2);
            z-index: 100;
        }

        .print-btn:hover { background: #2d8a9e; }