/* WR Exam Hub — single shared stylesheet. Mobile-first, no frameworks. */
:root{
  --navy:#123524; --navy-2:#1d4d33; --water:#2e7d4f; --water-dark:#1e5c39;
  --ink:#1d2b36; --muted:#5b6b78; --bg:#e2f2e2; --card:#ffffff;
  --line:#c6ddc8; --amber:#b45309; --amber-bg:#fef3e2; --green:#166534; --green-bg:#ecfdf3;
  --radius:10px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
  color:var(--ink);background:var(--bg);line-height:1.65;font-size:17px}
.wrap{max-width:1080px;margin:0 auto;padding:0 20px}
.content{max-width:780px;padding-top:28px;padding-bottom:8px}
h1,h2,h3{line-height:1.25;color:var(--navy);margin:1.4em 0 .6em}
h1{font-size:2rem;margin-top:.4em}
h2{font-size:1.45rem;border-bottom:2px solid var(--line);padding-bottom:.35em}
h3{font-size:1.15rem}
p{margin:.8em 0}
a{color:var(--water-dark)}
a:visited{color:var(--water-dark)}
main[aria-busy="true"]{opacity:.68;transition:opacity .15s ease}
.load-notice{background:var(--amber-bg);border:1px solid var(--amber);border-radius:8px;color:var(--ink);font-weight:700;margin:0 0 20px;padding:12px 16px}
.disclaimer-bar{background:var(--navy);color:#cfe0ee;font-size:.78rem;text-align:center;padding:8px 16px;line-height:1.4}
.site-header{background:var(--card);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:50}
.header-inner{display:flex;align-items:center;justify-content:space-between;gap:12px;padding:12px 20px;flex-wrap:wrap}
.brand{font-weight:800;font-size:1.25rem;color:var(--navy);text-decoration:none;display:inline-flex;align-items:center;gap:10px}
.brand-logo{width:32px;height:32px;border-radius:8px;display:block}
.brand-mark{color:var(--water)}
.site-nav{display:flex;gap:4px;flex-wrap:wrap}
.site-nav a{text-decoration:none;color:var(--ink);font-weight:600;font-size:.95rem;padding:8px 12px;border-radius:8px}
.site-nav a:hover{background:var(--bg)}
.site-nav a.active{color:var(--water-dark);background:#e4f1e7}
/* hero */
.hero{background:linear-gradient(135deg,var(--navy) 0%,var(--navy-2) 60%,var(--water-dark) 100%);
  color:#fff;padding:56px 0;margin:0 -20px 8px}
.hero .wrap{max-width:1080px}
.hero h1{color:#fff;font-size:2.4rem;margin:0 0 .4em;max-width:16em}
.hero p.lede{font-size:1.15rem;color:#d2e8d7;max-width:34em}
.hero-ctas{display:flex;gap:12px;flex-wrap:wrap;margin-top:20px;align-items:center}
.hero-pick{font-weight:700;color:#fff;margin:22px 0 0;font-size:1.05rem}
.hero-paths{display:flex;gap:12px;flex-wrap:wrap;margin-top:12px}
.hero-paths .btn{background:#fff;border-color:#fff;color:var(--navy);font-size:1.05rem;padding:14px 24px}
.hero-paths .btn:hover{background:#d2e8d7;border-color:#d2e8d7;color:var(--navy)}
.hero-textlink{color:#d2e8d7;font-weight:600}
.hero-textlink:visited{color:#d2e8d7} /* visited-state fix: a:visited (line 20) outranks .hero-textlink, so a visited hero link rendered dark-on-navy; confirmed by two visual QA runs */
/* Anchor offset so the sticky desktop header never covers a jumped-to heading (2026-10-20) */
#topics,#fe-path,#pe-path,#calculators{scroll-margin-top:84px}
.btn{display:inline-block;background:var(--water-dark);color:#fff;font-weight:700;text-decoration:none;
  padding:12px 22px;border-radius:9px;border:2px solid var(--water-dark)}
.btn:hover{background:var(--water-dark);border-color:var(--water-dark)}
.btn.ghost{background:transparent;border-color:#93c69f;color:#fff}
.btn.ghost:hover{background:rgba(255,255,255,.12)}
.btn.dark{background:var(--navy);border-color:var(--navy)}
/* steps */
.steps3{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:16px;margin:24px 0}
.step-card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:20px}
.step-num{display:inline-flex;width:34px;height:34px;border-radius:50%;background:var(--water-dark);color:#fff;
  font-weight:800;align-items:center;justify-content:center;margin-bottom:8px}
.step-card h3{margin:.2em 0 .4em}
/* topic cards */
.topic-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(240px,1fr));gap:16px;margin:24px 0}
.topic-card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:20px;
  text-decoration:none;color:var(--ink);display:flex;flex-direction:column;gap:6px}
.topic-card:hover{border-color:var(--water);box-shadow:0 4px 14px rgba(46,125,79,.12)}
.topic-card .t-num{font-size:.8rem;font-weight:800;color:var(--water);text-transform:uppercase;letter-spacing:.06em}
.topic-card h3{margin:0;font-size:1.05rem}
.topic-card p{margin:0;font-size:.92rem;color:var(--muted)}
/* formula + example + traps */
.formula-box{background:#e9f4ec;border:1px solid #bcdcc4;border-left:5px solid var(--water);
  border-radius:8px;padding:18px 20px;margin:22px 0}
.eq{font-size:1.25rem;text-align:center;margin:.5em 0;font-family:Georgia,"Times New Roman",serif}
.eq .frac{display:inline-block;vertical-align:middle;text-align:center;margin:0 .15em}
.eq .frac>span{display:block;padding:0 .35em}
.eq .frac>span:first-child{border-bottom:1.5px solid var(--ink)}
.var-table{width:100%;border-collapse:collapse;margin:10px 0 2px;font-size:.95rem}
.var-table td{padding:5px 8px;border-top:1px dashed #bcdcc4;vertical-align:top}
.var-table td:first-child{white-space:nowrap;font-weight:700;color:var(--navy-2)}
/* row-header cells: same look as the old first-column td (th defaults are bold+centred, which we keep bold but left-align) */
.var-table th[scope="row"]{padding:5px 8px;border-top:1px dashed #bcdcc4;vertical-align:top;
  white-space:nowrap;font-weight:700;color:var(--navy-2);text-align:left}
.formula-note{font-size:.9rem;color:var(--muted);margin-bottom:0}
.example-box{background:var(--green-bg);border:1px solid #bbe7c8;border-left:5px solid var(--green);
  border-radius:8px;padding:18px 20px;margin:22px 0}
.example-box h3{margin-top:0;color:var(--green)}
.example-box .steps li{margin-bottom:.55em}
.example-box .answer{background:#fff;border-radius:6px;padding:8px 12px;display:inline-block}
.tag{display:inline-block;background:var(--green);color:#fff;font-size:.72rem;font-weight:800;
  text-transform:uppercase;letter-spacing:.05em;border-radius:5px;padding:3px 9px;margin-right:8px;vertical-align:middle}
.tag.warn{background:var(--amber)}
.traps-box{background:var(--amber-bg);border:1px solid #f3d9a8;border-left:5px solid var(--amber);
  border-radius:8px;padding:18px 20px;margin:22px 0}
.traps-box h3{margin-top:0;color:var(--amber)}
.traps-box li{margin-bottom:.45em}
/* CTA */
.cta-box{background:var(--navy);color:#eaf2f9;border-radius:12px;padding:28px;margin:34px 0;text-align:center}
.cta-box h2{color:#fff;border:none;margin-top:0}
.cta-box h3{color:#fff;margin-top:0}
.cta-box a{color:#fff;text-decoration:underline}
.cta-box a:hover{color:#d8ecfa}
.cta-box p{color:#c9dcea;max-width:36em;margin-left:auto;margin-right:auto}
/* prev/next */
.prevnext-row{display:flex;justify-content:space-between;gap:12px;margin:34px 0;flex-wrap:wrap}
.prevnext{background:var(--card);border:1px solid var(--line);border-radius:8px;padding:10px 16px;
  text-decoration:none;font-weight:600;color:var(--navy-2);font-size:.95rem}
.prevnext:hover{border-color:var(--water)}
/* quiz cards */
.quiz-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(300px,1fr));gap:18px;margin:24px 0}
.quiz-card{background:var(--card);border:1px solid var(--line);border-radius:12px;padding:26px;display:flex;flex-direction:column;gap:10px}
.quiz-card .price{font-size:1.6rem;font-weight:800;color:var(--navy)}
.quiz-card h2{border:none;margin:0;padding:0}
.quiz-card ul{margin:.2em 0;padding-left:1.2em;font-size:.95rem}
.quiz-card .btn{margin-top:8px;text-align:center}
/* quiz sales page */
.sales-page{max-width:900px}
.quiz-feature{background:var(--card);border:2px solid var(--water);border-radius:12px;padding:28px;margin:28px 0}
.quiz-feature.flagship{border-width:3px;box-shadow:0 10px 28px rgba(14,124,196,.13)}
.quiz-feature.secondary{border-color:var(--line)}
.quiz-heading{display:flex;justify-content:space-between;align-items:flex-start;gap:20px;border-bottom:1px solid var(--line);padding-bottom:16px;margin-bottom:16px}
.quiz-heading h2{border:0;margin:.35em 0 0;padding:0}
.quiz-heading .price{font-size:2rem;font-weight:800;color:var(--navy);margin:0;white-space:nowrap}
.best-fit,.scope-label{display:inline-block;font-size:.76rem;font-weight:800;letter-spacing:.04em;text-transform:uppercase;border-radius:5px;padding:4px 9px}
.best-fit{background:var(--water-dark);color:#fff}.scope-label{background:var(--bg);color:var(--navy-2);border:1px solid var(--line)}
.quiz-details{display:grid;grid-template-columns:1.25fr 1fr;gap:24px;margin:18px 0 22px}
.quiz-details h3{margin:.1em 0 .55em}.quiz-details ul,.quiz-details ol{margin:0;padding-left:1.25em}.quiz-details li{margin-bottom:.45em}
.quiz-preview{background:var(--bg);border-radius:8px;padding:18px}
.buy-btn{display:block;text-align:center;font-size:1.05rem;padding:14px 20px}
.purchase-note{text-align:center;color:var(--muted);font-size:.83rem;margin:.55em 0 0}
.sales-disclaimer{background:var(--amber-bg);border:1px solid #e8c985;border-radius:8px;padding:14px 16px;margin:24px 0}
@media(max-width:640px){.quiz-feature{padding:20px 16px}.quiz-heading{align-items:end}.quiz-heading .price{font-size:1.6rem}.quiz-details{grid-template-columns:1fr}.buy-btn{width:100%}}

/* misc */
.breadcrumb{font-size:.85rem;color:var(--muted);margin-bottom:6px}
.breadcrumb a{color:var(--muted)}
.kicker{font-size:.85rem;font-weight:800;color:var(--water-dark);text-transform:uppercase;letter-spacing:.07em;margin-bottom:0}
.free-banner{background:#e9f4ec;border:1px solid #bcdcc4;border-radius:10px;padding:16px 20px;margin:22px 0}
.site-footer{background:var(--navy);color:#b9cede;margin-top:44px;padding:30px 0;font-size:.85rem}
.site-footer strong{color:#fff}
.foot-disclaimer{max-width:60em}
.foot-note{color:#8fa9c2}
/* tags, see-also, formula index */
.tags{list-style:none;display:flex;gap:8px;flex-wrap:wrap;padding:0;margin:12px 0 0}
.tags li{background:#e4f1e7;color:var(--water-dark);font-size:.78rem;font-weight:700;border-radius:20px;padding:4px 12px}
.seealso{background:var(--card);border:1px solid var(--line);border-radius:8px;padding:16px 20px;margin:26px 0}
.seealso h2{font-size:1.05rem;border:none;margin:0 0 .3em;padding:0}
.seealso ul{margin:.3em 0;padding-left:1.2em}
.seealso li{margin-bottom:.3em}
.index-topic{font-size:.82rem;font-weight:700;margin:0 0 2px;text-align:left}
.index-topic a{color:var(--water-dark);text-decoration:none}
.index-topic a:hover{text-decoration:underline}
.formula-jumps{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:8px;margin:22px 0 30px}
.formula-jumps a{background:var(--card);border:1px solid var(--line);border-radius:7px;padding:9px 11px;text-decoration:none;font-size:.88rem;font-weight:700}
.formula-jumps a:hover{border-color:var(--water)}
[id^="formula-topic-"],#formula-pe{scroll-margin-top:82px}
@media(min-width:720px){.formula-jumps{grid-template-columns:repeat(3,minmax(0,1fr))}}
@media (max-width:640px){
  body{font-size:16px}
  /* Mobile header fix (2026-10-20, Katharine's report): the sticky header
     covered most of the phone screen while scrolling. On small screens the
     header now scrolls away with the page instead of staying pinned. */
  .site-header{position:static}
  h1{font-size:1.65rem}
  .hero{padding:40px 0}
  .hero h1{font-size:1.9rem}
  .eq{font-size:1.1rem}
  .prevnext-row .prevnext{flex:1 1 100%;text-align:center}
}

/* Artifact presentation refinements: keyboard focus, narrow screens, and system dark mode. */
:root{color-scheme:light dark}
.site-nav{margin-left:auto}
a:focus-visible{outline:3px solid #f2a93b;outline-offset:3px;border-radius:4px}
.btn:focus-visible,.prevnext:focus-visible,.topic-card:focus-visible{outline-offset:4px}

/* Keyboard-focus audit (2026-10-17): every keyboard-focusable control shows a
   visible focus state in BOTH light and dark modes. The amber outline reads on
   light and dark backgrounds alike; no separate dark-mode rule is needed.
   Covers: quiz check buttons, calculator buttons, the homepage path filter,
   audio-narration buttons, FAQ summaries, and quiz radio labels (the label
   lights up when its inner radio has focus, mirroring the :checked pattern). */
.check-answer:focus-visible,.calc-btn:focus-visible,
.filter-btn:focus-visible,.audio-btn:focus-visible,
.faq-item summary:focus-visible{outline:3px solid #f2a93b;outline-offset:3px;border-radius:8px}
.quiz-options input:focus-visible{outline:3px solid #f2a93b;outline-offset:2px}
.quiz-options label:has(input:focus-visible){border-color:#f2a93b;box-shadow:0 0 0 2px #f2a93b}

/* Skip-link audit (2026-10-18): the first focusable element on every page
   (right after <body>, before the disclaimer bar). Visually hidden until it
   takes keyboard focus, then pinned to the top-left. Dark-navy background with
   white text reads at ~13:1 contrast on BOTH light and dark page backgrounds,
   so no dark-mode override is needed; the amber outline matches every other
   focus indicator on the site. tabindex="-1" on <main id="main"> moves focus
   along with the viewport in browsers that support it. */
.skip-link{position:absolute;left:1rem;top:-4rem;z-index:2000;
  background:#123524;color:#fff;font-weight:600;text-decoration:none;
  padding:.65rem 1.1rem;border-radius:8px;transition:top .15s ease}
.skip-link:visited{color:#fff}
.skip-link:focus-visible{top:1rem;outline:3px solid #f2a93b;outline-offset:2px}

/* External-link signal (2026-10-19): a small "opens elsewhere" arrow after
   every outbound text link (exam subdomain, Kit, YouTube, Telegram,
   NCEES). Background-image icon rather than generated text, so screen readers
   are not fed a decorative glyph; icon-only social SVG buttons are excluded
   via :has(svg), and same-site absolute links by the href guard. currentColor
   keeps the arrow readable in light, dark, and button contexts — no overrides. */
a[href^="https://"]:not([href^="https://waterresourceshub.com"]):not(:has(svg))::after{
  content:"";display:inline-block;width:.72em;height:.72em;margin-left:.2em;
  background:no-repeat center/contain url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16'%3E%3Cg fill='none' stroke='currentColor' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M3.5 12.5 12.5 3.5'/%3E%3Cpath d='M6.5 3.5h6v6'/%3E%3C/g%3E%3C/svg%3E")}
/* Reduced-motion guard (2026-10-21): users who set prefers-reduced-motion
   get no smooth scrolling, no hover/loading transitions, and no hover lift
   on the footer social icons — instant state changes instead. The scroll-behavior
   rule above (smooth for jump links) is already neutralised here; the three
   transition declarations (skip-link slide, social-icon hover, main loading
   fade) and the social-icon translateY also need explicit overrides. */
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  .skip-link,.social-row a,main[aria-busy="true"]{transition:none}
  .social-row a:hover{transform:none}
}
@media (max-width:520px){
  /* Compact mobile header (2026-10-20): the nav was a full-width vertical
     column (~300px tall) pinned by the sticky header. It is now a slim
     wrapping row, and the header itself is static at this width. */
  .header-inner{padding:8px 12px;gap:6px}
  .brand{font-size:1.05rem}
  .site-nav{width:100%;display:flex;flex-direction:row;flex-wrap:wrap;gap:2px;margin-left:0}
  .site-nav a{text-align:left;padding:6px 8px;font-size:.85rem}
  .site-nav a.exam-pill{white-space:nowrap;margin-left:0;padding:6px 12px}
  .hero-paths .btn{flex:1 1 100%;text-align:center}
  #topics,#fe-path,#pe-path,#calculators{scroll-margin-top:12px}
  .content{padding-left:16px;padding-right:16px}
  .hero{margin-left:-16px;margin-right:-16px}
  .topic-grid,.quiz-grid{grid-template-columns:1fr}
  .formula-box,.example-box,.traps-box{padding:16px 14px;margin-left:-4px;margin-right:-4px}
  .var-table,.var-table tbody{display:block;overflow:visible}
  .var-table tr{display:block;padding:8px 0;border-bottom:1px dashed var(--line)}
  .var-table tr:last-child{border-bottom:none}
  .var-table th[scope="row"]{display:block;white-space:normal;margin-bottom:2px}
  .var-table td,.var-table td:first-child{display:block;white-space:normal;overflow-wrap:anywhere}
  [id^="formula-topic-"],#formula-pe{scroll-margin-top:12px}
}
@media (prefers-color-scheme:dark){
  :root{
    --navy:#cdeeda;--navy-2:#a9d9bc;--water:#5cc583;--water-dark:#8fd6a8;
    --ink:#e8f4ea;--muted:#aecbb2;--bg:#0d1a10;--card:#152419;
    --line:#2c4632;--amber:#f3b65f;--amber-bg:#2a2115;--green:#75d59a;--green-bg:#13261c;
  }
  .disclaimer-bar,.site-footer,.cta-box{background:#091a10;color:#cfe4d2}
  .paid-preview{background:#123524}
  .btn.dark{background:#123524;border-color:#123524}
  .audio-btn{background:#123524}
  .site-header{background:#152419}
  .hero{background:linear-gradient(135deg,#08130b 0%,#123524 62%,#1e5c39 100%)}
  .hero p.lede{color:#d9efe0}
  .formula-box,.free-banner{background:#12291a;border-color:#2c5c3a}
  .formula-box{border-left-color:var(--water)}
  .var-table td,.var-table th[scope="row"]{border-color:#2c5c3a}
  .eq .frac>span:first-child{border-color:var(--ink)}
  .example-box{background:#13261c;border-color:#2f6544}
  .example-box .answer{background:#0e1d16}
  .traps-box{background:#2a2115;border-color:#624a26}
  .tags li,.site-nav a.active{background:#1a3524;color:#a9e5c0}
  .btn{color:#07130b}
  .btn.ghost{color:#fff}
  /* Contrast fix (2026-10-24): the hero path buttons keep a white background in
     both modes, but their text colour is var(--navy), which flips pale in dark
     mode (1.4:1 on white). Pin the light-mode navy so they stay readable. */
  .hero-paths .btn,.hero-paths .btn:hover{color:#123524}
  .site-footer strong,.cta-box h2{color:#fff}
  /* Dark-mode contrast fixes (2026-10-14 audit): the dark palette lightens the
     --water/--green/--amber backgrounds, so elements pairing white text with
     those backgrounds fall below WCAG contrast. Fixes verified by computation. */
  .btn.dark{color:#fff}
  .step-num,.best-fit{background:#0a6db3}
  .tag,.tag.warn{color:#07130b}
  .check-answer{color:#07130b}
  .audio-btn:hover{background:#0a6db3}
  .calc-field input,.calc-field select{background:#12291a;color:var(--ink);border-color:#2c5c3a}
  .calc-field input::placeholder{color:#8fa9c2}
  .calc-results{background:#12291a;border-color:#2c5c3a}
  .calc-results td,.calc-results th[scope="row"]{border-color:#2c5c3a}
  .calc-error{color:#ff9d9d}
}

/* Exam-specification map and FE-to-PE depth cues */
.level-row{display:flex;gap:7px;flex-wrap:wrap;margin:12px 0 18px}
.level-badge{display:inline-flex;align-items:center;border-radius:999px;padding:4px 10px;font-size:.74rem;font-weight:800;letter-spacing:.02em}
.level-fe{background:#e4f1e7;color:#075b90}
.level-both{background:#e8f7ee;color:#145f35}
.level-pe{background:#fff0d9;color:#8a4308}
.spec-note{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:18px 20px;margin:18px 0 26px}
.spec-note h2,.spec-note h3{border:0;padding:0;margin-top:0}
.spec-note p:last-child{margin-bottom:0}
.spec-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px;margin:20px 0}
.spec-card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:22px}
.spec-card h3{margin:.1em 0 .4em}
/* Heading-hierarchy audit (2026-10-22): the blueprint spec-card headings are
   top-level sections, so they are h2s now; spec-card h2 mirrors the old h3
   look (no base-h2 border) so nothing changes visually. */
.spec-card h2{font-size:1.15rem;border:none;padding-bottom:0;margin:.1em 0 .4em}
/* Heading-hierarchy audit (2026-10-22): screen-reader-only heading class for
   section labels that would duplicate a visible heading (e.g. the calculator
   card grid on calculators.html) — stays clipped in print too. */
.visually-hidden{position:absolute!important;width:1px;height:1px;margin:-1px;
  padding:0;border:0;clip:rect(0 0 0 0);clip-path:inset(50%);overflow:hidden;white-space:nowrap}
.spec-card ul{padding-left:1.2em;margin:.65em 0}
.spec-card li{margin:.4em 0}
.weight{font-variant-numeric:tabular-nums;font-weight:800;color:var(--water-dark);white-space:nowrap}
.depth-box{background:#fff7e8;border:1px solid #e8c985;border-left:5px solid var(--amber);border-radius:8px;padding:18px 20px;margin:24px 0}
.depth-box h2,.depth-box h3{border:0;padding:0;margin-top:0;color:var(--amber)}
.depth-box .formula-box{margin-bottom:8px}
.source-note{font-size:.88rem;color:var(--muted)}
.topic-card .level-row{margin:4px 0 2px}
.topic-card .level-badge{font-size:.67rem;padding:2px 8px}
@media(max-width:640px){.spec-grid{grid-template-columns:1fr}.spec-card{padding:18px}.depth-box{padding:16px 14px;margin-left:-4px;margin-right:-4px}}
@media(prefers-color-scheme:dark){
  .level-fe{background:#16364a;color:#9dd6f6}.level-both{background:#163a28;color:#91dfad}.level-pe{background:#3a2b17;color:#f3c77d}
  .depth-box{background:#2c2418;border-color:#6b522c}
}


/* free mini-quizzes */
.quiz-jump{margin:18px 0 26px}
.quiz-jump a{display:inline-block;background:var(--card);border:1px solid var(--water);border-radius:8px;padding:10px 14px;text-decoration:none;font-weight:800}
.mini-quiz{scroll-margin-top:88px;margin:34px 0;background:var(--card);border:1px solid var(--line);border-radius:12px;padding:28px}
.mini-quiz>h2{margin-top:.25em}
.quiz-question{border-top:1px solid var(--line);padding:18px 0 4px}
.quiz-question h3{margin:.2em 0 .55em}
.quiz-options{display:grid;gap:8px;margin:.6em 0 1em}
.quiz-options label{display:flex;align-items:flex-start;gap:10px;background:var(--bg);border:1px solid var(--line);border-radius:8px;padding:10px 12px;cursor:pointer}
.quiz-options label:has(input:checked){border-color:var(--water);background:#e9f4ec}
.quiz-options input{margin-top:.35em;accent-color:var(--water)}
.check-answer{appearance:none;background:var(--water-dark);border:2px solid var(--water-dark);border-radius:8px;color:#fff;font:inherit;font-weight:800;padding:8px 14px;cursor:pointer}
.check-answer:hover{background:var(--water-dark);border-color:var(--water-dark)}
.answer-feedback{border-radius:8px;padding:9px 13px;margin-top:9px}
.answer-feedback p{margin:0}
.answer-feedback.is-correct{background:var(--green-bg);border:1px solid var(--green)}
.answer-feedback.is-incorrect,.answer-feedback.needs-answer{background:var(--amber-bg);border:1px solid var(--amber)}
.mini-quiz-cta{background:var(--navy);color:#eaf2f9;border-radius:10px;padding:22px;margin-top:24px}
.mini-quiz-cta h3{color:#fff;margin:0 0 .3em}
.mini-quiz-cta p{color:#c9dcea}
.paid-quiz-links{display:flex;gap:10px;flex-wrap:wrap;margin-top:14px}
.paid-quiz-links .btn{flex:1 1 240px;text-align:center}
.free-quiz-directory{margin:30px 0 38px}
.free-quiz-directory>h2{margin-top:.25em}
.free-quiz-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:10px;margin-top:18px}
.free-quiz-card{display:flex;flex-direction:column;background:var(--card);border:1px solid var(--line);border-radius:8px;padding:14px 16px;text-decoration:none;color:var(--ink)}
.free-quiz-card:hover{border-color:var(--water)}
.free-quiz-card span{font-size:.74rem;font-weight:800;color:var(--water-dark);text-transform:uppercase;letter-spacing:.05em}
.free-quiz-card strong{color:var(--navy);margin:.1em 0}
.free-quiz-card small{color:var(--muted)}
@media(max-width:640px){.mini-quiz{padding:20px 15px;margin-left:-4px;margin-right:-4px}.free-quiz-grid{grid-template-columns:1fr}.paid-quiz-links{display:grid;grid-template-columns:1fr}}
@media(prefers-color-scheme:dark){.mini-quiz-cta{background:#091a10}.mini-quiz-cta h3{color:#fff}.quiz-options label:has(input:checked){background:#12291a}}

/* calculators */
.calc-box{background:var(--card);border:1px solid var(--line);border-radius:12px;padding:24px;margin:24px 0}
.calc-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(200px,1fr));gap:14px;margin:16px 0}
.calc-field{display:flex;flex-direction:column;gap:6px;font-size:.92rem;font-weight:600;color:var(--navy-2)}
.calc-field input,.calc-field select{font-size:1rem;padding:10px 12px;border:1px solid var(--line);border-radius:8px;background:#fff;color:var(--ink)}
.calc-field input:focus,.calc-field select:focus{outline:2px solid var(--water);border-color:var(--water)}
.calc-btn{margin-top:4px;cursor:pointer;font-size:1rem}
.calc-results{margin-top:18px;background:#e9f4ec;border:1px solid #bcdcc4;border-radius:8px;padding:16px 20px;display:none}
.calc-results.show{display:block}
.calc-results table{width:100%;border-collapse:collapse;font-size:.95rem}
.calc-results td,.calc-results th[scope="row"]{padding:6px 8px;border-top:1px dashed #bcdcc4}
.calc-results td:first-child,.calc-results th[scope="row"]{color:var(--muted);font-weight:400;text-align:left}
.calc-results td:last-child{font-weight:700;color:var(--navy);text-align:right}
.calc-error{color:#9c1c1c;font-weight:600}
.calc-note{font-size:.88rem;color:var(--muted);margin-top:14px}
/* FAQ */
.faq{margin:24px 0}
.faq-item{background:var(--card);border:1px solid var(--line);border-radius:10px;margin-bottom:12px;overflow:hidden}
.faq-item summary{cursor:pointer;font-weight:700;color:var(--navy);padding:16px 20px;list-style:none}
.faq-item summary::-webkit-details-marker{display:none}
.faq-item summary::after{content:"+";float:right;color:var(--water);font-size:1.3rem;line-height:1}
.faq-item[open] summary::after{content:"\2212"}
.faq-item .faq-a{padding:0 20px 18px;color:var(--ink)}
.faq-item .faq-a p{margin:.5em 0}
/* paid preview */
.paid-preview{background:var(--navy);color:#eaf2f9;border-radius:12px;padding:30px;margin:34px 0}
.paid-preview h2{color:#fff;border:none;margin-top:0}
.paid-preview p{color:#c9dcea}
.paid-preview .price{font-size:1.8rem;font-weight:800;color:#fff}
.sample-q{background:rgba(255,255,255,.07);border:1px solid rgba(255,255,255,.18);border-radius:10px;padding:20px;margin:18px 0;text-align:left}
.sample-q h3{color:#fff;margin-top:0}
.sample-q ol{color:#d2e8d7}
.sample-q .answer{color:#fff;background:rgba(255,255,255,.12);border-radius:6px;padding:8px 12px;display:inline-block;margin-top:8px}
/* footer links */
.site-footer a{color:#cfe0ee}

/* audio overview button */
.audio-overview{margin:1.1em 0}
.audio-btn{display:inline-flex;align-items:center;gap:.55em;background:var(--navy);color:#fff;border:none;border-radius:8px;padding:.62em 1.15em;font:inherit;font-weight:700;cursor:pointer}
.audio-btn:hover{background:var(--navy-2)}
.audio-btn .audio-icon{font-size:.85em}

/* Social icons in footer (matches exam site) */
.social-row{display:flex;gap:14px;align-items:center;margin:16px 0 6px}
.social-row a{display:inline-flex;width:34px;height:34px;border-radius:50%;background:#1b3a52;align-items:center;justify-content:center;transition:background .2s,transform .2s}
.social-row a:hover{background:#0B5FA5;transform:translateY(-2px)}
.social-row svg{width:18px;height:18px;fill:#d9efe0}

/* Exam Simulators pill in header (mirrors Learning Hub pill on exam site) */
.site-nav a.exam-pill{font-weight:700;color:var(--water-dark);border:1px solid var(--line);border-radius:999px;padding:8px 16px;white-space:nowrap;margin-left:6px}
.site-nav a.exam-pill:hover{background:var(--water-dark);color:#fff;border-color:var(--water-dark)}
@media (prefers-color-scheme:dark){
  .site-nav a.exam-pill{color:#8fd6a8;border-color:#2c4632}
  .site-nav a.exam-pill:hover{background:#0a6db3;color:#fff;border-color:#0a6db3}
}

/* Exam path filter */
.path-filter{display:flex;gap:10px;flex-wrap:wrap;margin:16px 0 6px}
.plan-tabs{display:flex;gap:10px;flex-wrap:wrap;margin:18px 0 4px}
.filter-btn{appearance:none;border:1px solid var(--line);background:var(--card);color:var(--ink);border-radius:999px;padding:9px 20px;font:inherit;font-weight:700;cursor:pointer}
.filter-btn:hover{border-color:var(--water)}
.filter-btn.active{background:var(--navy);border-color:var(--navy);color:#fff}
@media (prefers-color-scheme:dark){
  .filter-btn.active{background:#0a6db3;border-color:#0a6db3}
}

/* Dark-mode fix: .paid-preview base rule (line ~284) overrides the earlier
   dark-mode rule on source order; this late override restores the dark box. */
@media (prefers-color-scheme:dark){
  body .paid-preview{background:#123524;color:#eaf2f9}
  body .paid-preview h2{color:#fff}
  body .paid-preview p{color:#c9dcea}
  body .paid-preview .price{color:#fff}
}

/* Visited-state fix: keep button text readable after click.
   a:visited outranks .btn on specificity, so scope it explicitly. */
a.btn:visited{color:#fff}
a.btn.ghost:visited{color:#fff}
a.btn.dark:visited{color:#fff}
@media (prefers-color-scheme:dark){
  a.btn:visited{color:#07130b}
  a.btn.ghost:visited{color:#fff}
  a.btn.dark:visited{color:#fff}
}

/* PRINT — reference pages (formula index, calculators, cheat sheet) print cleanly.
   Site chrome (skip link, disclaimer bar, header, footer), interactive widgets
   (mini-quizzes, calculator/check buttons, exam-path filters, audio buttons),
   promos (cta-box, quiz-feature upsells, see-also) and prev/next sequence nav are
   hidden; dark-mode palettes are forced to black-on-white so a printout never
   wastes ink on dark backgrounds. Rolled out site-wide 2026-10-20 (daily site
   improvement: print stylesheet coverage) — replaces the page-local print block
   that used to live on open-channel-flow-cheat-sheet.html. */
@media print{
  body{background:#fff !important;color:#000 !important;font-size:11pt}
  h1,h2,h3,h4,.breadcrumb,.kicker{color:#000 !important}
  a,a:visited{color:#000 !important;text-decoration:underline}
  .wrap{max-width:none}
  .skip-link,.disclaimer-bar,.site-header,.site-footer,
  .mini-quiz,.mini-quiz-cta,.cta-box,.seealso,.prevnext-row,
  .print-note,.audio-btn,.check-answer,.calc-btn,.filter-btn,
  .path-filter,.plan-tabs,.quiz-feature,.load-notice{display:none !important}
}
.video-banner{background:#0b3c5d;color:#fff;text-align:center;padding:10px 16px;font-size:.95rem;line-height:1.45}
.video-banner a{color:#ffd23f;font-weight:700;text-decoration:underline}

/* KaTeX typeset math (auto-render, self-hosted assets/katex/) */
.katex-display{margin:.6em 0;padding:.1em 0;overflow-x:auto;overflow-y:hidden}
.eq .katex{font-size:1.02em}
.steps .katex,.example-box .katex{font-size:1.03em}

/* Transportation hub home components (from the WRH hub pattern) */
.hub-jumps{display:flex;flex-wrap:wrap;gap:8px;margin:18px 0 6px}
.hub-jumps a{background:var(--card);border:1px solid var(--line);border-radius:7px;padding:9px 11px;text-decoration:none;font-size:.88rem;font-weight:700}
.map-table{width:100%;border-collapse:collapse;margin:14px 0 22px;font-size:.95rem}
.map-table th,.map-table td{border:1px solid var(--line);padding:9px 11px;text-align:left;vertical-align:top}
.map-table th{background:var(--card)}
.ep-list{list-style:none;padding:0;margin:14px 0}
.ep-list li{background:var(--card);border:1px solid var(--line);border-radius:8px;padding:13px 16px;margin:0 0 10px}
.ep-list .ep-num{font-size:.78rem;font-weight:800;text-transform:uppercase;letter-spacing:.06em;color:var(--water)}
.ep-list p{margin:.25em 0 0;color:var(--muted);font-size:.93rem}