/* engineerexamlab.com: "lab notebook" (light paper, navy ink, one amber accent, dark calc-pad problem blocks).
   Tokens first; one radius scale (10px blocks, 999px buttons); no frameworks; no JS. */
:root {
  --ink: #0B1F3A;
  --ink-2: #2E3D57;
  --muted: #5A6781;
  --paper: #F6F7F9;
  --card: #FFFFFF;
  --line: #DCE1E9;
  --amber: #F5B700;
  --amber-soft: #FFF4CC;
  --pad: #0E1A2E;
  --pad-2: #15253F;
  --pad-text: #E9EEF6;
  --pad-dim: #A3B0C5;
  --radius: 10px;
  --serif: "Source Serif 4", "Source Serif Pro", Georgia, "Times New Roman", serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--paper); color: var(--ink); font: 400 17px/1.65 var(--sans); }
@media (min-width: 760px) { body { font-size: 18px; } }
img { max-width: 100%; height: auto; }
a { color: var(--ink); text-decoration: underline; text-decoration-color: var(--amber); text-decoration-thickness: 2px; text-underline-offset: 3px; }
a:hover { background: var(--amber-soft); }
:focus-visible { outline: 3px solid var(--amber); outline-offset: 2px; }
.skip { position: absolute; left: -9999px; }
.skip:focus { left: 16px; top: 8px; background: var(--card); padding: 8px 12px; z-index: 10; }
.wrap { max-width: 1160px; margin: 0 auto; padding: 0 16px; }
.wrap-narrow { max-width: 760px; margin: 0 auto; padding: 0 16px; }

/* header */
.site-header { background: var(--card); border-bottom: 1px solid var(--line); }
.header-row { display: flex; align-items: center; gap: 20px; min-height: 64px; }
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; font-size: 14px; white-space: nowrap; }
.brand img { border-radius: 7px; }
.brand:hover { background: none; }
.nav { display: none; gap: 22px; margin-left: auto; }
.nav a { text-decoration: none; font-weight: 600; font-size: 15px; color: var(--ink-2); padding: 4px 0; border-bottom: 2px solid transparent; }
.nav a:hover, .nav a[aria-current="page"] { background: none; color: var(--ink); border-bottom-color: var(--amber); }
.btn { display: inline-block; text-decoration: none; font-weight: 700; border-radius: 999px; padding: 12px 22px; white-space: nowrap; transition: transform .15s ease, box-shadow .15s ease; }
.btn:active { transform: translateY(1px); }
.btn-primary, .btn-small { background: var(--amber); color: var(--ink); box-shadow: 0 1px 0 rgba(11, 31, 58, .25); }
.btn-primary:hover, .btn-small:hover { background: #FFC81F; box-shadow: 0 4px 14px rgba(245, 183, 0, .35); }
.btn-small { padding: 8px 16px; font-size: 14px; margin-left: auto; }
.btn-ghost { border: 2px solid var(--ink); color: var(--ink); }
.btn-ghost:hover { background: var(--ink); color: var(--card); }
.menu { position: relative; }
.menu summary { list-style: none; cursor: pointer; font-weight: 700; font-size: 14px; padding: 8px 12px; border: 1px solid var(--line); border-radius: 999px; }
.menu summary::-webkit-details-marker { display: none; }
.menu nav { position: absolute; right: 0; top: 46px; background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 8px; display: grid; min-width: 200px; box-shadow: 0 12px 30px rgba(11, 31, 58, .12); z-index: 5; }
.menu nav a { text-decoration: none; padding: 10px 12px; border-radius: 6px; font-weight: 600; }
@media (max-width: 420px) { .btn-small { display: none; } .menu { margin-left: auto; } }
@media (min-width: 900px) { .nav { display: flex; } .menu { display: none; } .btn-small { margin-left: 6px; } }

/* article */
.article { padding: 28px 16px 56px; }
.crumbs { font-size: 14px; color: var(--muted); margin-bottom: 14px; }
.crumbs a { color: var(--muted); text-decoration-color: var(--line); }
h1, h2, h3 { font-family: var(--serif); color: var(--ink); line-height: 1.18; text-wrap: balance; }
h1 { font-size: clamp(30px, 6vw, 44px); font-weight: 700; margin: 0 0 12px; letter-spacing: -.01em; }
h2 { font-size: clamp(23px, 3.6vw, 29px); font-weight: 700; margin: 44px 0 12px; }
h3 { font-size: 20px; font-weight: 600; margin: 28px 0 8px; }
.byline { color: var(--muted); font-size: 15px; margin: 0 0 22px; }
.prose { max-width: 72ch; }
.prose p, .prose li { text-wrap: pretty; }
.prose .lead { font-size: 1.12em; color: var(--ink); border-left: 4px solid var(--amber); padding: 4px 0 4px 16px; margin: 0 0 26px; }
.prose ul, .prose ol { padding-left: 1.3em; }
.prose li { margin: 6px 0; }
.prose code { font-family: var(--mono); font-size: .9em; background: #EEF1F5; padding: 1px 5px; border-radius: 5px; }
.table-wrap { overflow-x: auto; margin: 18px 0 24px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--card); }
table { border-collapse: collapse; width: 100%; font-size: 15.5px; font-variant-numeric: tabular-nums; }
th, td { text-align: left; padding: 10px 14px; vertical-align: top; }
thead th { background: #EEF1F5; font-weight: 700; border-bottom: 1px solid var(--line); }
tbody tr + tr td { border-top: 1px solid #EDF0F4; }
.toc { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 14px 18px; margin: 0 0 28px; max-width: 72ch; }
.toc-h, .related-h { font-weight: 700; margin: 0 0 6px; font-size: 15px; }
.toc ol { margin: 0; padding-left: 1.2em; font-size: 15.5px; }
.toc li { margin: 3px 0; }
.faq .qa { border-top: 1px solid var(--line); padding-top: 4px; }
.faq h3 { font-family: var(--sans); font-size: 18px; font-weight: 700; }
.sources ol { font-size: 15px; color: var(--ink-2); padding-left: 1.4em; }
.sources li { margin: 6px 0; word-break: break-word; }
.related { max-width: 72ch; margin-top: 34px; border-top: 1px solid var(--line); padding-top: 18px; }
.related ul { margin: 0; padding-left: 1.2em; }

/* membership block (exactly one per page) */
.cta { background: var(--ink); color: var(--pad-text); border-radius: 14px; padding: 26px 24px; margin: 42px 0; }
.cta-title { font-family: var(--serif); font-weight: 700; font-size: 26px; line-height: 1.2; color: #fff; margin: 0 0 6px; }
.cta-sub { color: var(--pad-dim); margin: 0 0 14px; font-size: 16px; }
.cta-list, .prose .cta-list { list-style: none; padding: 0; margin: 0 0 16px; }
.cta-list li { padding-left: 22px; position: relative; margin: 8px 0; }
.cta-list li::before { content: ""; position: absolute; left: 2px; top: .62em; width: 9px; height: 9px; border-radius: 2px; background: var(--amber); }
.cta-list strong { color: #fff; }
.cta-tiers { display: grid; gap: 8px; margin: 0 0 18px; }
.cta-tiers p { margin: 0; background: var(--pad-2); border-radius: 8px; padding: 10px 14px; font-family: var(--mono); font-size: 14.5px; }
.cta-tiers span { color: var(--amber); font-weight: 500; margin-right: 6px; }
.cta-fine { color: var(--pad-dim); font-size: 14px; margin: 12px 0 0; }
@media (min-width: 760px) { .cta { padding: 32px 34px; } .cta-tiers { grid-template-columns: 1fr 1fr; } }

/* problem blocks (engine output) */
.problem { background: var(--pad); color: var(--pad-text); border-radius: var(--radius); padding: 20px 20px 16px; margin: 22px 0; font-size: 16px; }
.problem-label { font-family: var(--mono); color: var(--amber); font-size: 13px; letter-spacing: .04em; margin: 0 0 10px; text-transform: uppercase; }
.problem-label .sep { color: var(--pad-dim); }
.problem-stem { margin: 0 0 12px; line-height: 1.6; }
.options, .prose .options { list-style: none; padding: 0; margin: 0 0 12px; display: grid; gap: 6px; font-family: var(--mono); font-size: 15px; }
.options li { background: var(--pad-2); border-radius: 7px; padding: 8px 12px; }
.options b { color: var(--amber); margin-right: 8px; font-weight: 500; }
.fill { font-family: var(--mono); font-size: 14.5px; color: var(--pad-dim); margin: 0 0 12px; }
.problem-hb { font-family: var(--mono); font-size: 13.5px; color: var(--pad-dim); margin: 0 0 10px; }
.solution summary { cursor: pointer; color: var(--amber); font-weight: 700; padding: 8px 0; list-style: none; }
.solution summary::-webkit-details-marker { display: none; }
.solution summary::before { content: "+ "; font-family: var(--mono); }
.solution[open] summary::before { content: "- "; }
.sol { margin: 8px 0 4px; display: grid; grid-template-columns: 1fr; gap: 2px 16px; font-size: 15px; }
.sol dt { font-family: var(--mono); color: var(--amber); font-size: 12.5px; text-transform: uppercase; letter-spacing: .05em; margin-top: 10px; }
.sol dd { margin: 0; }
.sol code { font-family: var(--mono); font-size: 14px; color: var(--pad-text); background: none; padding: 0; white-space: pre-wrap; }
.sol ol.steps { margin: 4px 0; padding-left: 1.2em; }
.sol ul { margin: 4px 0; padding-left: 1.1em; }
@media (min-width: 760px) { .problem { padding: 24px 26px 18px; } .sol { grid-template-columns: 140px 1fr; } .sol dt { margin-top: 6px; } }

/* hubs */
.hub-group { margin: 34px 0; max-width: 900px; }
.hub-list, .prose .hub-list { list-style: none; padding: 0; margin: 0; display: grid; gap: 0; border-top: 1px solid var(--line); }
.hub-list li { padding: 14px 0; border-bottom: 1px solid var(--line); display: grid; gap: 2px; }
.hub-list a, .hub-list .unlinked { font-weight: 700; font-size: 17px; }
.hub-list span { color: var(--muted); font-size: 15px; }
@media (min-width: 900px) { .hub-list { grid-template-columns: 1fr 1fr; column-gap: 36px; } }

/* home */
.home .hero { padding: 44px 0 30px; }
.hero-grid { display: grid; gap: 30px; align-items: start; }
.hero h1 { font-size: clamp(34px, 6.4vw, 54px); margin-bottom: 14px; }
.hero h1 em { font-style: normal; background: linear-gradient(transparent 62%, var(--amber-soft) 62%); }
.hero-sub { font-size: 19px; color: var(--ink-2); max-width: 34ch; margin: 0 0 22px; }
.hero-ctas { display: flex; gap: 12px; flex-wrap: wrap; }
.hero .problem { margin: 0; box-shadow: 0 24px 48px rgba(11, 31, 58, .18); }
@media (min-width: 980px) { .hero-grid { grid-template-columns: 1.05fr 1fr; gap: 48px; } .home .hero { padding: 64px 0 40px; } }
.facts-strip { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1px; background: var(--line); border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; margin: 10px 0 0; }
.facts-strip > a, .facts-strip > .unlinked { background: var(--card); padding: 16px 16px 14px; text-decoration: none; display: block; }
.facts-strip a:hover { background: var(--amber-soft); }
.facts-strip b { display: block; font-family: var(--mono); font-weight: 500; font-size: 26px; color: var(--ink); }
.facts-strip span { color: var(--muted); font-size: 14.5px; }
@media (min-width: 760px) { .facts-strip { grid-template-columns: repeat(4, 1fr); } }
.home-section { padding: 40px 0; }
.home-section h2 { margin-top: 0; }
.split { display: grid; gap: 26px; }
@media (min-width: 900px) { .split { grid-template-columns: 1fr 1fr; gap: 44px; } }
.schedule { list-style: none; padding: 0; margin: 0; border-left: 3px solid var(--amber); }
.schedule li { padding: 0 0 18px 18px; position: relative; }
.schedule li b { display: block; font-family: var(--mono); font-weight: 500; font-size: 14px; color: var(--muted); }
.home .prose-wide { max-width: 72ch; }
.method { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 22px 22px; }
.method ol { margin: 0; padding-left: 1.2em; }

/* footer */
.site-footer { background: var(--ink); color: var(--pad-dim); margin-top: 40px; padding: 40px 0 26px; font-size: 15px; }
.site-footer a { color: #fff; text-decoration-color: rgba(245, 183, 0, .6); }
.site-footer a:hover { background: none; color: var(--amber); }
.footer-grid { display: grid; gap: 24px; }
.footer-grid nav { display: grid; gap: 6px; align-content: start; }
.footer-brand { display: flex; align-items: center; gap: 10px; color: #fff; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; font-size: 14px; }
.footer-brand img { border-radius: 6px; }
.footer-h { color: #fff; font-weight: 700; margin: 0 0 4px; }
.footer-legal { border-top: 1px solid rgba(255, 255, 255, .12); margin-top: 26px; padding-top: 16px; font-size: 13.5px; }
@media (min-width: 760px) { .footer-grid { grid-template-columns: 2fr 1fr 1fr; } }
@media (prefers-reduced-motion: reduce) { * { transition: none !important; } }
@media print { .site-header, .site-footer, .cta, .toc { display: none; } .problem { color: #000; background: #fff; border: 1px solid #999; } }

/* 2026-10-03: visible non-affiliation notice on every page */
.site-notice{margin:0;padding:.55rem 0;font-size:.9rem;line-height:1.4;background:#F3EFE4;color:#2b2b2b;border-bottom:1px solid #E3DCC9;text-align:center}
.site-notice .wrap{display:block;padding:0 1rem}
.site-notice a{color:inherit;text-decoration:underline}