/* WR Exam Hub — single shared stylesheet. Mobile-first, no frameworks. */
:root{
  --navy:#0e2a44; --navy-2:#143a5c; --water:#0e7cc4; --water-dark:#0a5f96;
  --ink:#1d2b36; --muted:#5b6b78; --bg:#f6f9fb; --card:#ffffff;
  --line:#dbe5ec; --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)}
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}
.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:#e8f3fa}
/* 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:#d7e7f4;max-width:34em}
.hero-ctas{display:flex;gap:12px;flex-wrap:wrap;margin-top:20px}
.btn{display:inline-block;background:var(--water);color:#fff;font-weight:700;text-decoration:none;
  padding:12px 22px;border-radius:9px;border:2px solid var(--water)}
.btn:hover{background:var(--water-dark);border-color:var(--water-dark)}
.btn.ghost{background:transparent;border-color:#9cc6e2;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);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(14,124,196,.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:#eaf4fb;border:1px solid #bcd9ee;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 #bcd9ee;vertical-align:top}
.var-table td:first-child{white-space:nowrap;font-weight:700;color:var(--navy-2)}
.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 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);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:#eaf4fb;border:1px solid #bcd9ee;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:#e8f3fa;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}
  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}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}}
@media (max-width:520px){
  .header-inner{padding:8px 12px}
  .site-nav{width:100%;display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:4px}
  .site-nav a{text-align:center;padding:8px 6px;font-size:.86rem}
  .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{display:block;overflow:visible}
  .var-table tr{display:grid;grid-template-columns:minmax(3rem,auto) 1fr}
  .var-table td,.var-table td:first-child{white-space:normal;overflow-wrap:anywhere}
  [id^="formula-topic-"],#formula-pe{scroll-margin-top:176px}
}
@media (prefers-color-scheme:dark){
  :root{
    --navy:#b9ddf7;--navy-2:#8fcaf2;--water:#52afe7;--water-dark:#83c8f2;
    --ink:#e7eef4;--muted:#b3c1cc;--bg:#101820;--card:#17232c;
    --line:#344652;--amber:#f3b65f;--amber-bg:#2a2115;--green:#75d59a;--green-bg:#13261c;
  }
  .disclaimer-bar,.site-footer,.cta-box{background:#09131b;color:#c3d2dc}
  .site-header{background:#17232c}
  .hero{background:linear-gradient(135deg,#091c2b 0%,#103452 62%,#0a5a84 100%)}
  .hero p.lede{color:#d9eaf5}
  .formula-box,.free-banner{background:#122b3b;border-color:#285570}
  .formula-box{border-left-color:var(--water)}
  .var-table td{border-color:#285570}
  .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:#1a3445;color:#9ed5f5}
  .btn{color:#07131b}
  .btn.ghost{color:#fff}
  .site-footer strong,.cta-box h2{color:#fff}
}

/* 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:#e8f3fa;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}
.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:#eaf4fb}
.quiz-options input{margin-top:.35em;accent-color:var(--water)}
.check-answer{appearance:none;background:var(--water);border:2px solid var(--water);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:#09131b}.mini-quiz-cta h3{color:#fff}.quiz-options label:has(input:checked){background:#122b3b}}

/* 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:#eaf4fb;border:1px solid #bcd9ee;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{padding:6px 8px;border-top:1px dashed #bcd9ee}
.calc-results td:first-child{color:var(--muted)}
.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:#d7e7f4}
.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}