:root {
            --page-bg: var(--warm-50);
            --page-color: var(--slate-700);
            --site-nav-bg: rgba(250, 249, 247, 0.85);
            --site-nav-padding: 0 32px;
            --site-nav-gap: 0;
            --nav-links-gap: 28px;
            --nav-link-hover: var(--teal-700);
            --footer-padding: 56px 32px 28px;
            --footer-inner-max: 1080px;
            --footer-top-gap: 40px;
            --footer-top-margin: 44px;
            --footer-tablet-gap: 28px;
            --footer-mobile-padding: 40px 16px 24px;
            --footer-tagline-max: 300px;
            --footer-heading-color: rgba(255, 255, 255, .85);
            --footer-legal-max: 620px;
        }

        html {
            overflow-x: visible;
        }

        .citation {
            text-decoration: underline
        }

        body.article-wide {
            --article-head-max: 1200px;
            --deck-max: 960px;
        }

        body.article-compact {
            --article-head-max: 800px;
            --deck-max: 660px;
        }

        /* NAV */
        .nav-left {
            display: flex;
            align-items: center;
            gap: 14px;
        }

        .nav-sep {
            width: 1px;
            height: 20px;
            background: var(--slate-200);
        }

        .nav-blogtag {
            font-size: 13.5px;
            font-weight: 600;
            color: var(--slate-500);
            letter-spacing: 0.01em;
        }

        .nav-back {
            display: inline-flex;
            align-items: center;
            gap: 7px;
            font-size: 13.5px;
            font-weight: 600;
            color: var(--slate-600);
            padding: 7px 14px;
            border: 1px solid var(--slate-200);
            border-radius: 8px;
            background: #fff;
            transition: border-color .15s, color .15s;
        }

        .nav-back:hover {
            border-color: var(--teal-200);
            color: var(--teal-700);
        }

        /* reading progress */
        .progress-rail {
            position: fixed;
            top: 60px;
            left: 0;
            right: 0;
            height: 2px;
            z-index: 99;
            background: transparent;
        }

        .progress-bar {
            height: 100%;
            width: 0%;
            background: var(--teal-500);
            transition: width .1s linear;
        }

        /* ARTICLE HEADER */
        .article-head {
            max-width: var(--article-head-max, 1120px);
            margin: 0 auto;
            padding: 72px 32px 0;
            text-align: center;
        }

        h1.title {
            font-size: clamp(34px, 4.6vw, 52px);
            font-weight: 700;
            line-height: 1.08;
            letter-spacing: -0.032em;
            color: var(--slate-900);
            text-wrap: balance;
            margin-bottom: 24px;
        }

        .deck {
            font-size: clamp(18px, 2.1vw, 21px);
            line-height: 1.55;
            color: var(--slate-600);
            font-weight: 400;
            max-width: var(--deck-max, 880px);
            margin: 0 auto 36px;
            text-wrap: pretty;
        }

        .byline {
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 14px;
            padding-bottom: 4px;
        }

        .byline-mark {
            width: 42px;
            height: 42px;
            border-radius: 50%;
            background: var(--teal-50);
            border: 1px solid var(--teal-100);
            display: flex;
            align-items: center;
            justify-content: center;
            flex-shrink: 0;
        }
        .byline-mark img {
            width: 24px;
            height: 24px;
            display: block;
        }

        .byline-text {
            text-align: left;
        }

        .byline-author {
            font-size: 14px;
            font-weight: 600;
            color: var(--slate-800);
            white-space: nowrap;
        }

        .byline-meta {
            font-size: 13px;
            color: var(--slate-500);
            margin-top: 2px;
            white-space: nowrap;
        }

        .byline-meta .dot {
            color: var(--slate-300);
            margin: 0 7px;
        }

        /* HERO FIGURE */
        .hero-figure {
            max-width: 1080px;
            margin: 44px auto 0;
            padding: 0 32px;
        }

        .hero-frame {
            background: linear-gradient(165deg, var(--slate-100) 0%, var(--warm-100) 100%);
            border: 1px solid var(--slate-200);
            border-radius: 18px;
            padding: 20px;
            box-shadow: 0 4px 6px rgba(13, 20, 40, 0.03), 0 24px 64px rgba(13, 20, 40, 0.08);
        }

        .hero-frame img {
            width: 100%;
            display: block;
            border-radius: 6px;
        }

        .hero-cap {
            max-width: 720px;
            margin: 16px auto 0;
            font-size: 13.5px;
            line-height: 1.55;
            color: var(--slate-500);
            text-align: center;
            text-wrap: pretty;
        }

        .hero-cap b {
            color: var(--slate-700);
            font-weight: 600;
        }

        /* BODY LAYOUT */
        .layout {
            max-width: 1080px;
            margin: 0 auto;
            padding: 56px 32px 96px;
            display: grid;
            grid-template-columns: 232px minmax(0, 1fr);
            gap: 64px;
            align-items: start;
        }

        /* TOC */
        .toc {
            position: sticky;
            top: 92px;
            align-self: start;
        }

        .toc-label {
            font-size: 11px;
            font-weight: 700;
            letter-spacing: 0.1em;
            text-transform: uppercase;
            color: var(--slate-400);
            margin-bottom: 14px;
            padding-left: 14px;
        }

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

        .toc li {
            counter-increment: toc;
        }

        .toc a {
            display: grid;
            grid-template-columns: 22px 1fr;
            gap: 4px;
            padding: 7px 14px;
            font-size: 13px;
            line-height: 1.4;
            color: var(--slate-500);
            border-left: 2px solid var(--slate-200);
            transition: color .15s, border-color .15s;
        }

        .toc a::before {
            content: counter(toc, decimal-leading-zero);
            font-family: var(--mono);
            font-size: 11px;
            color: var(--slate-400);
            font-weight: 500;
        }

        .toc a:hover {
            color: var(--slate-800);
        }

        .toc a.active {
            color: var(--teal-700);
            font-weight: 600;
            border-left-color: var(--teal-500);
        }

        .toc a.active::before {
            color: var(--teal-600);
        }

        /* TOC drawer base. */
        .toc-summary {
            list-style: none;
            pointer-events: none;
            display: flex;
            align-items: center;
        }

        .toc-summary::-webkit-details-marker { display: none; }

        .toc-chevron { display: none; }

        /* ARTICLE PROSE */
        .prose {
            max-width: var(--measure);
            min-width: 0;
        }

        .prose > p {
            font-size: 17.5px;
            line-height: 1.78;
            color: var(--slate-700);
            margin-bottom: 22px;
            text-wrap: pretty;
            text-align: justify;
        }

        .prose .lead-first::first-letter {
            initial-letter: 3;
            -webkit-initial-letter: 3;
            font-weight: 700;
            color: var(--slate-900);
            margin-right: 12px;
        }

        .prose h2 {
            font-size: clamp(25px, 2.8vw, 31px);
            font-weight: 700;
            line-height: 1.2;
            letter-spacing: -0.025em;
            color: var(--slate-900);
            margin: 60px 0 8px;
            scroll-margin-top: 84px;
            text-wrap: balance;
        }

        .prose h2 .h2-num {
            display: block;
            font-family: var(--mono);
            font-size: 12.5px;
            font-weight: 500;
            letter-spacing: 0.06em;
            color: var(--teal-600);
            margin-bottom: 12px;
        }

        .prose h2 + p {
            margin-top: 18px;
        }


        .prose h3 {
            font-size: 20px;
            line-height: 1.3;
            letter-spacing: -0.015em;
            color: var(--slate-900);
            margin: 36px 0 12px;
            font-weight: 700;
        }

        .prose strong {
            color: var(--slate-900);
            font-weight: 600;
        }

        .prose em {
            font-style: italic;
        }

        .prose a.ref {
            color: var(--teal-700);
            font-weight: 500;
            border-bottom: 1px solid var(--teal-200);
        }

        .prose a.ref:hover {
            border-bottom-color: var(--teal-600);
        }

        .prose code {
            font-family: var(--mono);
            font-size: 0.88em;
            background: var(--slate-100);
            color: var(--slate-800);
            padding: 1.5px 6px;
            border-radius: 5px;
            border: 1px solid var(--slate-200);
            white-space: nowrap;
        }

        .formula {
            display: block;
            font-family: var(--mono);
            font-size: 15px;
            color: var(--slate-800);
            background: var(--warm-100);
            border: 1px solid var(--warm-200);
            border-radius: 8px;
            padding: 14px 18px;
            margin: 6px 0 22px;
            text-align: center;
            white-space: nowrap;
            overflow-x: auto;
        }

        /* Section divider rule under h2 group intro. */
        .kicker-rule {
            height: 1px;
            background: var(--slate-200);
            margin: 4px 0 0;
        }

        /* KEY-POINT CALLOUT */
        .callout {
            display: grid;
            grid-template-columns: 34px 1fr;
            gap: 14px;
            background: var(--teal-50);
            border: 1px solid var(--teal-100);
            border-radius: 14px;
            padding: 20px 22px;
            margin: 28px 0;
        }

        .callout .ic {
            width: 34px;
            height: 34px;
            border-radius: 9px;
            background: #fff;
            border: 1px solid var(--teal-200);
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .callout .c-label {
            font-size: 11px;
            font-weight: 700;
            letter-spacing: 0.08em;
            text-transform: uppercase;
            color: var(--teal-700);
            margin-bottom: 5px;
        }

        .callout p {
            font-size: 15px;
            line-height: 1.6;
            color: var(--slate-700);
            margin: 0;
        }

        .callout p strong {
            color: var(--teal-800);
        }

        /* amber variant for "common mistake" */
        .callout.warn {
            background: var(--amber-50);
            border-color: var(--amber-100);
        }

        .callout.warn .ic {
            border-color: #FDE9B8;
        }

        .callout.warn .c-label {
            color: var(--amber-700);
        }

        .callout.warn p strong {
            color: var(--amber-700);
        }

        /* PULL EMPHASIS */
        .pull {
            margin: 36px 0;
            padding: 4px 0 4px 26px;
            border-left: 3px solid var(--teal-500);
        }

        .pull p {
            font-size: clamp(20px, 2.4vw, 25px);
            line-height: 1.35;
            letter-spacing: -0.02em;
            color: var(--slate-900);
            font-weight: 600;
            text-wrap: balance;
            margin: 0;
        }

        /* BASELINE SUMMARY CARD */
        .baseline {
            background: #fff;
            border: 1px solid var(--slate-200);
            border-radius: 16px;
            padding: 4px;
            margin: 30px 0;
            box-shadow: 0 1px 2px rgba(13, 20, 40, 0.04);
        }

        .baseline-head {
            display: flex;
            align-items: center;
            gap: 10px;
            padding: 16px 20px 14px;
        }

        .baseline-head .bh-title {
            font-size: 14px;
            font-weight: 700;
            color: var(--slate-900);
        }

        .baseline-head .bh-sub {
            font-size: 12.5px;
            color: var(--slate-500);
        }

        .baseline-grid {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 1px;
            background: var(--slate-200);
            border-radius: 12px;
            overflow: hidden;
        }

        .baseline-cell {
            background: #fff;
            padding: 18px 20px;
        }

        .baseline-cell .bc-tag {
            display: inline-block;
            font-size: 10.5px;
            font-weight: 700;
            letter-spacing: 0.06em;
            text-transform: uppercase;
            padding: 3px 9px;
            border-radius: 100px;
            margin-bottom: 10px;
        }

        .baseline-cell.osha .bc-tag {
            background: var(--teal-50);
            color: var(--teal-700);
            border: 1px solid var(--teal-100);
        }

        .baseline-cell.un .bc-tag {
            background: var(--slate-100);
            color: var(--slate-600);
            border: 1px solid var(--slate-200);
        }

        .baseline-cell .bc-rev {
            font-size: 22px;
            font-weight: 700;
            color: var(--slate-900);
            letter-spacing: -0.02em;
            line-height: 1.1;
            margin-bottom: 8px;
        }

        .baseline-cell .bc-rev span {
            color: var(--slate-400);
            font-weight: 500;
            font-size: 14px;
        }

        .baseline-cell ul {
            list-style: none;
            display: flex;
            flex-direction: column;
            gap: 6px;
        }

        .baseline-cell li {
            font-size: 12.5px;
            line-height: 1.45;
            color: var(--slate-600);
            display: grid;
            grid-template-columns: 14px 1fr;
            gap: 7px;
            align-items: start;
        }

        .baseline-cell li .m {
            color: var(--teal-600);
            font-weight: 700;
        }

        .baseline-cell.un li .m {
            color: var(--slate-400);
        }

        /* DATA TABLE */
        .table-wrap {
            margin: 30px 0;
        }

        .table-scroll {
            overflow-x: auto;
            border: 1px solid var(--slate-200);
            border-radius: 14px;
            background: #fff;
        }

        table.data {
            width: 100%;
            border-collapse: collapse;
            font-size: 13.5px;
            min-width: 660px;
        }

        table.data thead th {
            background: var(--slate-50);
            color: var(--slate-700);
            font-weight: 600;
            font-size: 12.5px;
            text-align: center;
            padding: 13px 14px;
            border-bottom: 1px solid var(--slate-200);
            white-space: nowrap;
        }

        table.data thead th:first-child {
            text-align: left;
        }

        table.data thead th .sub {
            display: block;
            font-size: 10px;
            font-weight: 600;
            letter-spacing: 0.05em;
            text-transform: uppercase;
            color: var(--slate-400);
            margin-top: 3px;
        }

        table.data tbody th {
            text-align: left;
            font-weight: 600;
            color: var(--slate-800);
            padding: 12px 14px;
            border-bottom: 1px solid var(--slate-100);
            white-space: nowrap;
        }

        table.data tbody td {
            text-align: center;
            padding: 12px 14px;
            border-bottom: 1px solid var(--slate-100);
            color: var(--slate-600);
            font-variant-numeric: tabular-nums;
            white-space: nowrap;
        }

        table.data tbody tr:last-child th, table.data tbody tr:last-child td {
            border-bottom: none;
        }

        table.data tbody tr:hover th, table.data tbody tr:hover td {
            background: var(--slate-50);
        }

        /* highlight GHS-only column */
        table.data .col-ghs {
            background: var(--teal-50) !important;
            color: var(--teal-800);
            font-weight: 500;
        }

        table.data thead th.col-ghs {
            background: var(--teal-100) !important;
            color: var(--teal-800);
        }

        table.data thead th.col-ghs .sub {
            color: var(--teal-600);
        }

        .osha-band {
            position: relative;
        }

        .table-legend {
            display: flex;
            flex-wrap: wrap;
            gap: 16px;
            margin-top: 12px;
            font-size: 12.5px;
            color: var(--slate-500);
        }

        .table-legend span {
            display: inline-flex;
            align-items: center;
            gap: 7px;
        }

        .table-legend .sw {
            width: 12px;
            height: 12px;
            border-radius: 3px;
        }

        .table-legend .sw.osha {
            background: #fff;
            border: 1px solid var(--slate-300);
        }

        .table-legend .sw.ghs {
            background: var(--teal-100);
            border: 1px solid var(--teal-200);
        }

        /* DECISION RULES */
        .rules {
            display: flex;
            flex-direction: column;
            gap: 16px;
            margin: 32px 0 0;
        }

        .rule {
            display: grid;
            grid-template-columns: 44px 1fr;
            gap: 18px;
            background: #fff;
            border: 1px solid var(--slate-200);
            border-radius: 14px;
            padding: 22px 24px;
            transition: border-color .2s, box-shadow .2s;
        }

        .rule:hover {
            border-color: var(--teal-200);
            box-shadow: 0 8px 32px rgba(13, 20, 40, 0.07);
        }

        .rule-num {
            width: 44px;
            height: 44px;
            border-radius: 50%;
            background: var(--teal-600);
            color: #fff;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 17px;
            font-weight: 700;
            flex-shrink: 0;
            box-shadow: 0 0 0 5px rgba(13, 148, 136, 0.10);
        }

        .rule-body p {
            font-size: 15.5px;
            line-height: 1.62;
            color: var(--slate-700);
            margin: 0;
        }

        .rule-body p strong {
            color: var(--slate-900);
        }

        .rule-lede {
            display: block;
            font-size: 14px;
            font-weight: 700;
            color: var(--slate-900);
            margin-bottom: 5px;
            letter-spacing: -0.01em;
        }

        /* ARTICLE FOOTER NOTE */
        .article-note {
            max-width: var(--measure);
            margin: 56px 0 0;
            padding: 22px 24px;
            background: var(--warm-100);
            border: 1px solid var(--warm-200);
            border-radius: 14px;
        }

        .article-note .an-label {
            font-size: 11px;
            font-weight: 700;
            letter-spacing: 0.08em;
            text-transform: uppercase;
            color: var(--slate-500);
            margin-bottom: 8px;
        }

        .article-note p {
            font-size: 13.5px;
            line-height: 1.65;
            color: var(--slate-600);
            margin: 0;
        }

        .article-note p + p {
            margin-top: 10px;
        }

        /* RESPONSIVE */

        /* Smaller laptop: max 1079px. */
        @media (max-width: 1079px) {
            .layout {
                grid-template-columns: 200px minmax(0, 1fr);
                gap: 48px;
            }
        }

        /* Tablet / phone landscape: max 920px. */
        @media (max-width: 920px) {
            .layout {
                grid-template-columns: minmax(0, 1fr);
                gap: 0;
                padding-top: 40px;
            }

            .toc {
                position: static;
                margin-bottom: 32px;
            }

            .toc-drawer {
                background: #fff;
                border: 1px solid var(--slate-200);
                border-radius: 14px;
                overflow: hidden;
            }

            .toc-summary {
                pointer-events: auto;
                cursor: pointer;
                justify-content: space-between;
                padding: 14px 18px;
                user-select: none;
                border-bottom: 1px solid transparent;
                transition: border-color .15s;
            }

            .toc-drawer[open] .toc-summary {
                border-bottom-color: var(--slate-100);
            }

            .toc-label {
                font-size: 13px;
                font-weight: 600;
                color: var(--slate-700);
                letter-spacing: 0;
                text-transform: none;
                margin-bottom: 0;
                padding-left: 0;
            }

            .toc-chevron {
                display: block;
                color: var(--slate-400);
                transition: transform .2s;
                flex-shrink: 0;
            }

            .toc-drawer[open] .toc-chevron {
                transform: rotate(180deg);
            }

            .toc-drawer > nav {
                padding: 0 8px 8px;
            }

            .hero-figure {
                margin-top: 36px;
            }

        }

        /* Phone landscape / small tablet portrait: max 640px. */
        @media (max-width: 640px) {
            nav.site-nav {
                padding: 0 20px;
            }

            .nav-blogtag {
                display: none;
            }

            .article-head {
                padding: 44px 20px 0;
            }

            .hero-figure,
            .layout {
                padding-left: 20px;
                padding-right: 20px;
            }

            .hero-frame {
                padding: 14px;
            }

            .prose > p {
                font-size: 16.5px;
            }

            .prose h2 {
                margin-top: 48px;
            }

            .callout {
                padding: 16px 18px;
                gap: 12px;
            }

            .pull {
                margin: 28px 0;
                padding-left: 20px;
            }

            .pull p {
                font-size: clamp(18px, 5vw, 22px);
            }

            .rule {
                padding: 18px 20px;
                gap: 14px;
            }

            table.data {
                font-size: 12.5px;
                min-width: 480px;
            }

            table.data thead th,
            table.data tbody th,
            table.data tbody td {
                padding: 10px 12px;
            }
        }

        /* Phone portrait: max 480px. */
        @media (max-width: 480px) {
            .nav-links {
                display: none;
            }

            .article-head {
                padding: 36px 16px 0;
            }

            .hero-figure,
            .layout {
                padding-left: 16px;
                padding-right: 16px;
            }

            .hero-frame {
                padding: 10px;
                border-radius: 14px;
            }

            .hero-cap {
                font-size: 12.5px;
            }

            .prose > p {
                font-size: 16px;
                line-height: 1.72;
            }

            .prose h2 {
                margin-top: 40px;
                scroll-margin-top: 72px;
            }

            .byline {
                flex-direction: column;
                align-items: center;
                justify-content: center;
                gap: 8px;
            }

            .byline-text {
                text-align: center;
            }

            .byline-author,
            .byline-meta {
                white-space: normal;
            }

            .callout {
                grid-template-columns: 30px 1fr;
                gap: 10px;
                padding: 14px 16px;
            }

            .callout .ic {
                width: 30px;
                height: 30px;
                border-radius: 7px;
            }

            .rule {
                grid-template-columns: 36px 1fr;
                gap: 12px;
                padding: 16px;
            }

            .rule-num {
                width: 36px;
                height: 36px;
                font-size: 14px;
                box-shadow: 0 0 0 4px rgba(13, 148, 136, 0.10);
            }

            .article-note {
                padding: 18px;
            }

        }