:root {
  --bg: #eef0f8;
  --panel: #eef0f8;
  --surface: #f2f4fa;
  --text: #252830;
  --muted: #62697c;
  --line: #cdd3e1;
  --accent: #9f5543;
  --gold: var(--accent);
  --serif: Georgia, "Times New Roman", serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --shadow-card: 10px 12px 26px rgba(165, 174, 195, .24), -8px -8px 24px rgba(255, 255, 255, .85);
  --shadow-control: 3px 4px 8px rgba(154, 163, 183, .30), -3px -3px 8px rgba(255, 255, 255, .90);
  --shadow-inset: inset 2px 2px 5px rgba(160, 169, 188, .19), inset -2px -2px 5px rgba(255, 255, 255, .75);
  color-scheme: light;
  font-family: -apple-system, BlinkMacSystemFont, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  -webkit-font-smoothing: antialiased;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 108px; }
body { margin: 0; background: var(--bg); }
button, input, select { font: inherit; }
button, a, input, summary { -webkit-tap-highlight-color: transparent; }
a { color: inherit; }
button { cursor: pointer; }
a:focus-visible, button:focus-visible, input:focus-visible, select:focus-visible, summary:focus-visible, [tabindex]:focus-visible { outline: 3px solid var(--gold); outline-offset: 5px; }
button:disabled { cursor: default; opacity: .45; }
.page-width { max-width: 1380px; margin-inline: auto; padding-inline: clamp(20px, 5vw, 76px); }
.visually-hidden { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; border: 0; }
.skip-link { position: fixed; left: 20px; top: -90px; padding: 12px 18px; background: var(--accent); color: #fff; border-radius: 12px; z-index: 100; }
.skip-link:focus { top: 12px; }
.site-header { position: sticky; z-index: 20; top: 0; background: rgba(238, 240, 248, .94); border-bottom: 1px solid rgba(190, 199, 216, .5); display: flex; align-items: center; justify-content: space-between; gap: 26px; padding: 22px clamp(22px, 4vw, 60px); backdrop-filter: blur(18px); -webkit-backdrop-filter: blur(18px); }
.brand { text-decoration: none; display: flex; align-items: center; gap: 12px; font-size: 24px; letter-spacing: -.035em; line-height: 1; white-space: nowrap; font-family: var(--serif); font-weight: 400; }
.brand b { font-weight: 400; color: var(--accent); }
.brand small { font-size: 10px; display: inline-block; letter-spacing: .16em; margin-left: 12px; color: var(--muted); font-family: var(--mono); }
.brand-mark { display: block; width: 29px; height: 29px; border: 1px solid var(--line); border-radius: 50%; position: relative; box-shadow: var(--shadow-control); }
.brand-mark::before, .brand-mark::after { content: ""; position: absolute; border: 1px solid var(--line); border-radius: 50%; inset: 5px; }
.brand-mark::after { inset: 10px; background: var(--accent); border-color: var(--accent); }
.primary-nav { display: flex; align-items: center; gap: 28px; }
.primary-nav a, .header-link { text-decoration: none; color: var(--muted); font-size: 13px; white-space: nowrap; }
.primary-nav a:hover, .primary-nav a.is-active, .header-link:hover { color: var(--gold); }
.header-link span { margin-left: 8px; }

.hero-copy { max-width: 980px; margin-inline: auto; }
.hero-cinema { width: 100%; margin: 0; }
.hero-cinema img { display: block; width: 100%; aspect-ratio: 16 / 9; object-fit: cover; border-radius: 24px; box-shadow: var(--shadow-card); }
.hero-cinema figcaption { display: flex; justify-content: space-between; gap: 12px 28px; flex-wrap: wrap; margin: 16px auto 0; font-family: var(--mono); font-size: 10px; letter-spacing: .06em; line-height: 1.75; color: var(--muted); text-align: left; }
.cinema-intro { margin-top: 52px; padding: clamp(24px, 4vw, 42px); background: var(--panel); border-radius: 28px; box-shadow: var(--shadow-card); }
.cinema-intro-copy { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); align-items: start; gap: 18px 42px; margin-bottom: 34px; }
.cinema-intro-copy h2 { font-family: var(--serif); font-size: clamp(29px, 3vw, 44px); font-weight: 400; line-height: 1.16; letter-spacing: -.035em; margin: 0; }
.cinema-intro-copy .eyebrow { grid-column: 1; grid-row: 1; margin: 0; }
.cinema-intro-copy h2 { grid-column: 1; grid-row: 2; }
.cinema-intro-copy p:not(.eyebrow) { grid-column: 2; grid-row: 1 / span 3; font-size: 15px; line-height: 1.8; color: #4b5060; margin: 0; padding-top: 28px; }
.cinema-intro-copy .text-link { grid-column: 1; grid-row: 3; justify-self: start; }
.cinema-gallery { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 18px; }
.cinema-shot { margin: 0; min-width: 0; }
.cinema-shot :is(img,svg) { display: block; width: 100%; aspect-ratio: 16 / 9; object-fit: cover; border-radius: 16px; overflow: hidden; }
.cinema-shot figcaption { padding: 13px 2px 0; font-size: 12px; line-height: 1.7; color: var(--muted); }
.cinema-shot figcaption small { display: block; font-family: var(--mono); font-size: 9px; letter-spacing: .1em; margin-bottom: 8px; }
.cinema-shot figcaption p { margin: 0; }
.cinema-shot figcaption strong, .cinema-shot figcaption b { display: block; font-family: var(--serif); font-weight: 400; font-size: 20px; color: var(--text); margin-bottom: 4px; }
.lesson-nav-group { margin-top: 24px; }
.lesson-group-title { margin: 0 0 9px; padding-inline: 12px; font-family: var(--mono); font-weight: 400; font-size: 10px; letter-spacing: .12em; line-height: 1.7; color: var(--muted); text-transform: uppercase; }
.track-nav { display: flex; flex-wrap: wrap; gap: 8px; margin: 0 0 24px; }
.track-nav a, .track-nav button { padding: 12px 18px; min-height: 44px; border: 1px solid var(--line); border-radius: 999px; background: var(--panel); color: var(--muted); text-decoration: none; font-family: var(--mono); font-size: 12px; letter-spacing: .04em; }
.track-nav a.is-active, .track-nav button[aria-selected="true"] { color: var(--accent); box-shadow: var(--shadow-control); border-color: transparent; }

.hero { display: grid; grid-template-columns: minmax(0, 1fr); gap: 46px; padding-top: 76px; padding-bottom: 64px; align-items: center; text-align: center; }
.eyebrow { font-size: 11px; line-height: 1.6; letter-spacing: .15em; font-weight: 400; color: var(--muted); margin: 0 0 22px; font-family: var(--mono); }
.live-dot { display: inline-block; background: var(--gold); height: 5px; width: 5px; border-radius: 50%; margin: 0 8px 2px 0; }
h1 { margin: 0 auto; font-size: clamp(44px, 5.6vw, 78px); line-height: 1.07; font-weight: 400; letter-spacing: -.045em; max-width: 980px; font-family: var(--serif); text-wrap: balance; }
h1 em { color: var(--accent); font-style: normal; }
.hero-description { font-size: 18px; line-height: 1.75; color: var(--muted); max-width: 760px; margin: 28px auto 30px; }
.hero-actions { display: flex; align-items: center; flex-wrap: wrap; gap: 20px 25px; justify-content: center; }
.button { display: inline-flex; justify-content: center; align-items: center; gap: 18px; padding: 14px 23px; min-height: 47px; text-decoration: none; font-size: 12px; font-weight: 600; border: 1px solid transparent; border-radius: 999px; font-family: var(--mono); letter-spacing: .05em; }
.button-gold { color: var(--accent); background: var(--panel); box-shadow: var(--shadow-control); }
.button-gold:hover { background: var(--surface); box-shadow: var(--shadow-inset); }
.button-outline { color: var(--muted); background: transparent; border-color: var(--line); border: 1px dashed var(--line); }
.button-outline:hover { border-color: var(--gold); color: var(--gold); }
.text-link { display: inline-flex; gap: 12px; align-items: center; text-decoration: none; font-size: 14px; border-bottom: 0; padding: 6px 0; color: var(--accent); }
.text-link:hover { color: var(--gold); }
.founder-note { color: var(--muted); font-size: 12px; line-height: 1.8; max-width: 760px; margin: 26px auto 0; }
.founder-note a { color: var(--accent); text-underline-offset: 3px; }
.hero-demo { border: 0; border-radius: 28px; background: var(--panel); padding: 27px; box-shadow: var(--shadow-card); max-width: 620px; width: 100%; margin-inline: auto; text-align: left; }
.demo-top { display: flex; justify-content: space-between; gap: 20px; color: var(--muted); font-size: 11px; letter-spacing: .12em; }
.mono { font-family: ui-monospace, SFMono-Regular, Consolas, monospace; white-space: nowrap; }
.aperture-comparison { display: flex; align-items: center; justify-content: center; gap: 23px; padding: 48px 0 39px; }
.aperture-comparison > div { display: flex; align-items: center; flex-direction: column; }
.aperture-ring { width: 121px; height: 121px; border-radius: 50%; background: var(--panel); display: grid; place-items: center; border: 1px solid var(--line); box-shadow: var(--shadow-card); }
.aperture-open { display: block; width: 72px; height: 72px; background: var(--gold); border-radius: 50%; }
.aperture-closed { display: block; width: 50.4px; height: 50.4px; background: var(--gold); border-radius: 50%; }
.aperture-comparison strong { font-size: 27px; font-weight: 400; letter-spacing: -.04em; margin-top: 23px; font-family: var(--serif); }
.aperture-comparison small { font-size: 11px; color: var(--muted); margin-top: 8px; }
.demo-arrow { color: var(--muted); font-size: 29px; margin-top: -46px; }
.demo-math { border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); display: flex; align-items: center; gap: 24px; padding: 17px 0; }
.demo-math strong { font-size: 61px; font-weight: 400; letter-spacing: -.06em; color: var(--gold); font-family: var(--serif); }
.demo-math strong span { font-size: 12px; letter-spacing: 0; display: inline-block; margin-left: 7px; }
.demo-math p { font-size: 13px; color: var(--muted); line-height: 1.7; }
.demo-link { display: flex; justify-content: space-between; align-items: center; padding-top: 19px; text-decoration: none; font-size: 13px; color: var(--gold); }
.demo-caption { font-size: 11px; color: var(--muted); line-height: 1.6; margin: 12px 0 0; }
.learning-facts { display: flex; justify-content: space-between; align-items: center; gap: 25px; border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); padding-top: 24px; padding-bottom: 24px; color: var(--muted); font-size: 13px; }
.learning-facts b { color: var(--text); font-size: 27px; font-weight: 400; margin-right: 9px; font-family: var(--serif); }
.facts-philosophy { color: var(--muted); font-size: 12px; }
.facts-philosophy i { color: var(--gold); font-style: normal; margin-inline: 9px; }
.site-search { padding-top: 30px; }
.site-search > label { display: flex; align-items: center; gap: 15px; background: var(--panel); border: 1px solid rgba(205, 211, 225, .6); border-radius: 16px; padding: 12px 18px; box-shadow: var(--shadow-inset); }
.site-search label > span { font-size: 26px; color: var(--gold); line-height: 1; }
.site-search input { flex: 1; min-width: 0; background: transparent; border: 0; color: var(--text); font-size: 15px; line-height: 1.6; padding: 6px 0; }
.site-search input::placeholder { color: var(--muted); }
.search-results { padding: 18px 22px; border: 1px solid var(--line); border-top: 0; background: var(--surface); border-radius: 16px; margin-top: 10px; box-shadow: var(--shadow-card); }
.search-results p { font-size: 13px; color: var(--muted); line-height: 1.7; margin-top: 0; }
.search-results ul { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: 1fr 1fr; gap: 8px 22px; }
.search-results a { display: block; text-decoration: none; padding: 9px 0; color: var(--text); font-size: 14px; }
.search-results small { display: block; font-size: 11px; letter-spacing: .09em; color: var(--gold); margin-bottom: 5px; }
.section-heading { display: flex; justify-content: space-between; align-items: end; gap: 55px; padding-bottom: 35px; }
.section-heading h2 { font-size: clamp(31px, 3.5vw, 49px); letter-spacing: -.035em; font-weight: 400; line-height: 1.12; margin: 0; max-width: 700px; font-family: var(--serif); }
.section-heading .eyebrow { margin-bottom: 16px; }
.section-heading > p { flex: 0 0 310px; color: var(--muted); font-size: 15px; line-height: 1.8; margin: 0 0 3px; }
.course-section, .experiment-section, .guide-section, .glossary-section, .sources-section { padding-top: 95px; }
.course-layout { display: grid; grid-template-columns: 260px minmax(0, 1fr); gap: 42px; align-items: start; }
.course-sidebar { position: sticky; top: 110px; }
.course-sidebar summary { color: var(--text); font-size: 12px; font-weight: 400; display: flex; justify-content: space-between; align-items: center; cursor: pointer; padding: 0 0 19px; border-bottom: 1px solid var(--line); font-family: var(--mono); letter-spacing: .06em; }
.course-sidebar summary::-webkit-details-marker { display: none; }
.course-sidebar summary span { font: 11px ui-monospace, monospace; color: var(--gold); }
.lesson-nav-link { display: flex; align-items: start; gap: 11px; padding: 12px; border-bottom: 0; border-left: 2px solid transparent; text-decoration: none; font-size: 13px; color: var(--muted); line-height: 1.45; border-radius: 10px; margin: 2px 0; }
.lesson-nav-link > span { font: 10px ui-monospace, monospace; color: var(--muted); padding-top: 3px; width: 17px; flex-shrink: 0; }
.lesson-nav-link b { font-weight: 400; }
.lesson-nav-link.is-active { border-left-color: transparent; background: var(--panel); color: var(--accent); box-shadow: var(--shadow-control); }
.lesson-nav-link:hover { color: var(--gold); }
.lesson-content { border: 1px solid rgba(205, 211, 225, .3); border-radius: 28px; background: var(--panel); padding: clamp(24px, 4vw, 48px); box-shadow: var(--shadow-card); }
.lesson-meta { display: flex; flex-wrap: wrap; gap: 9px 20px; color: var(--muted); font-size: 11px; margin-bottom: 21px; font-family: var(--mono); letter-spacing: .045em; }
.lesson-meta .lesson-number { color: var(--gold); }
.lesson-content h3 { margin: 0 0 22px; font-weight: 400; font-size: clamp(29px, 3.4vw, 44px); line-height: 1.18; letter-spacing: -.03em; font-family: var(--serif); }
.lesson-body p, .guide-body p { font-size: 16px; line-height: 1.85; color: #4b5060; margin: 0 0 20px; }
.lesson-background { margin: 26px 0; padding: 0 20px; border: 1px solid rgba(205, 211, 225, .65); border-radius: 16px; background: var(--surface); }
.lesson-background > summary { padding: 16px 0; cursor: pointer; color: var(--text); font-size: 15px; line-height: 1.7; }
.lesson-background > .lesson-body { padding-top: 15px; }
.lesson-section-title { display: flex; align-items: center; gap: 12px; margin: 36px 0 17px; color: var(--text); font-size: 24px; font-weight: 400; letter-spacing: -.02em; font-family: var(--serif); }
.lesson-section-title small { font: 10px ui-monospace, monospace; color: var(--gold); letter-spacing: .03em; font-family: var(--mono); font-size: 11px; }
.lesson-experiment { padding: 24px; margin: 29px 0; border: 1px solid rgba(205, 211, 225, .65); border-radius: 18px; background: var(--surface); }
.lesson-experiment p { margin: 0 0 12px; color: var(--muted); font-size: 14px; line-height: 1.7; }
.app-steps { padding-left: 23px; margin: 0; }
.app-steps li, .limits-list li { color: #4b5060; font-size: 15px; line-height: 1.8; padding: 5px 0 5px 8px; }
.app-steps li::marker { color: var(--gold); font-size: 12px; }
.tips-grid { display: grid; gap: 11px; }
.tip { padding: 0 20px; background: var(--surface); border: 1px solid rgba(205, 211, 225, .65); border-radius: 16px; }
.tip summary { padding: 16px 0; cursor: pointer; color: var(--text); font-size: 15px; line-height: 1.7; }
.tip summary small { display: block; color: var(--muted); font-size: 10px; line-height: 1.8; letter-spacing: .04em; margin-bottom: 5px; font-family: var(--mono); }
.tip p { color: #4b5060; font-size: 14px; line-height: 1.8; margin: 0 0 15px; }
.tip p b { color: var(--text); font-weight: 500; }
.limits-list { margin: 0; padding-left: 17px; }
.lesson-bottom { display: flex; gap: 15px; justify-content: space-between; align-items: center; border-top: 1px solid var(--line); margin-top: 33px; padding-top: 25px; }
.lesson-bottom button { background: transparent; border: 0; color: var(--muted); font-size: 13px; padding: 10px 0; text-align: left; }
.lesson-bottom button:last-child { color: var(--gold); text-align: right; }
.experiment-tabs { display: flex; gap: 8px; flex-wrap: wrap; margin: 2px 0 22px; padding: 8px; background: var(--panel); border: 1px solid var(--line); border-radius: 22px; box-shadow: var(--shadow-inset); width: fit-content; max-width: 100%; }
.experiment-tabs button { border: 1px solid transparent; background: transparent; padding: 11px 18px; min-height: 44px; font-size: 12px; color: var(--muted); border-radius: 999px; font-family: var(--mono); letter-spacing: .03em; }
.experiment-tabs button[aria-selected="true"] { color: var(--accent); background: var(--panel); border-color: transparent; font-weight: 400; box-shadow: var(--shadow-control); }
.model-note { color: var(--muted); font-size: 12px; line-height: 1.8; margin: 18px 0 0; max-width: 750px; }
.guide-toolbar { display: flex; align-items: center; flex-wrap: wrap; gap: 15px 22px; margin-bottom: 26px; }
.file-type { color: var(--muted); font-family: ui-monospace, monospace; font-size: 11px; }
.guide-chapter { border-top: 1px solid var(--line); }
.guide-chapter:last-child { border-bottom: 1px solid var(--line); }
.guide-chapter > summary { font-size: 22px; line-height: 1.6; color: var(--text); cursor: pointer; padding: 22px 2px; font-family: var(--serif); }
.guide-chapter > summary .chapter-number { color: var(--gold); font: 11px ui-monospace, monospace; margin-right: 19px; }
.guide-body { padding: 8px 0 26px; max-width: 900px; margin-left: 43px; }
.guide-body h3 { font-size: 21px; color: var(--text); line-height: 1.5; font-weight: 400; margin: 28px 0 14px; font-family: var(--serif); }
.guide-body ul, .guide-body ol { padding-left: 22px; }
.guide-body li { color: #4b5060; font-size: 15px; line-height: 1.85; padding: 4px 0; }
.glossary-search { display: block; max-width: 520px; }
.glossary-search input { background: var(--panel); border: 1px solid var(--line); border-radius: 14px; color: var(--text); min-height: 47px; width: 100%; padding: 12px 16px; font-size: 15px; box-shadow: var(--shadow-inset); }
.result-count { color: var(--muted); font-size: 11px; margin: 14px 0 26px; }
.glossary-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 28px 32px; margin: 0; }
.glossary-item { border-top: 1px solid var(--line); padding-top: 20px; }
.glossary-item dt { color: var(--text); font-size: 22px; line-height: 1.5; letter-spacing: -.025em; margin-bottom: 11px; font-family: var(--serif); }
.glossary-item dd { margin: 0; color: #4b5060; font-size: 14px; line-height: 1.9; }
.glossary-item.is-highlighted { border-color: var(--gold); background: var(--surface); padding: 20px 15px; border-radius: 16px; box-shadow: var(--shadow-control); }
.sources-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 25px; }
.source-card { border: 1px solid rgba(205, 211, 225, .45); border-radius: 20px; padding: 24px; background: var(--panel); box-shadow: var(--shadow-control); }
.source-card a { display: flex; gap: 12px; align-items: start; justify-content: space-between; font-size: 17px; color: var(--text); line-height: 1.7; text-decoration: none; font-family: var(--serif); }
.source-card a span { color: var(--gold); }
.source-card p { font-size: 13px; color: var(--muted); line-height: 1.9; margin: 15px 0 0; }
.source-card a:hover { color: var(--gold); }
.site-footer { margin-top: 90px; padding-top: 37px; padding-bottom: 45px; border-top: 1px solid var(--line); display: flex; justify-content: space-between; gap: 35px; flex-wrap: wrap; }
.footer-brand { font-size: 24px; letter-spacing: -.035em; text-decoration: none; font-family: var(--serif); }
.footer-brand span { font-size: 10px; color: var(--gold); letter-spacing: .12em; margin-left: 13px; font-family: var(--mono); }
.site-footer p { color: var(--muted); font-size: 12px; line-height: 1.8; margin-top: 12px; }
.site-footer nav { display: flex; gap: 25px; align-items: start; }
.site-footer nav a { color: var(--muted); font-size: 12px; text-decoration: none; }
.site-footer small { width: 100%; color: var(--muted); font-size: 11px; line-height: 1.8; }
.no-script { padding: 24px; border: 1px solid var(--gold); margin: 25px; color: var(--text); line-height: 1.8; }
.print-appendix { display: none; }
@media (min-width: 1100px) { .course-sidebar details { max-height: calc(100vh - 133px); overflow-y: auto; padding-right: 8px; scrollbar-width: thin; } }
@media (max-width: 1100px) { .header-link { display: none; } .primary-nav { gap: 20px; } .facts-philosophy { display: none; } .section-heading > p { flex-basis: 270px; } .course-layout { grid-template-columns: 220px minmax(0,1fr); gap: 28px; } .sources-grid { grid-template-columns: repeat(2, minmax(0,1fr)); } }
@media (max-width: 820px) {
  html { scroll-padding-top: 135px; }
  .site-header { flex-wrap: wrap; gap: 16px; padding-top: 18px; padding-bottom: 12px; }
  .primary-nav { width: 100%; justify-content: space-between; gap: 20px; overflow-x: auto; padding-bottom: 4px; }
  .hero { padding-top: 56px; gap: 34px; }
  h1 { font-size: clamp(42px, 7.6vw, 64px); }
  .hero-description { font-size: 17px; }
  .hero-demo { max-width: 520px; width: 100%; }
  .hero-cinema img { border-radius: 20px; }
  .aperture-comparison { gap: 30px; }
  .cinema-intro-copy { grid-template-columns: minmax(0,1fr); gap: 18px; }
  .cinema-intro-copy .eyebrow, .cinema-intro-copy h2, .cinema-intro-copy p:not(.eyebrow), .cinema-intro-copy .text-link { grid-column: auto; grid-row: auto; }
  .cinema-intro-copy p:not(.eyebrow) { padding-top: 0; }
  .cinema-gallery { gap: 12px; }
  .course-layout { grid-template-columns: minmax(0,1fr); }
  .course-sidebar { position: static; }
  #lesson-nav { display: grid; grid-template-columns: repeat(2,minmax(0,1fr)); gap: 0 20px; }
  .lesson-nav-group { min-width: 0; }
  .course-sidebar summary::before { content: "+"; color: var(--muted); font-weight: 400; margin-right: 12px; }
  .course-sidebar details[open] summary::before { content: "−"; }
  .course-sidebar summary #route-count { margin-left: auto; }
  .section-heading { display: block; }
  .section-heading > p { margin-top: 20px; max-width: 580px; }
  .learning-facts { gap: 16px; }
  .learning-facts span { font-size: 12px; }
  .learning-facts b { font-size: 23px; }
  .glossary-grid { grid-template-columns: repeat(2,minmax(0,1fr)); }
  .course-section, .experiment-section, .guide-section, .glossary-section, .sources-section { padding-top: 72px; }
  .guide-body { margin-left: 0; }
  .search-results ul { grid-template-columns: minmax(0,1fr); }
}
@media (max-width: 520px) {
  .cinema-gallery { grid-template-columns: minmax(0,1fr); gap: 22px; }
  #lesson-nav { grid-template-columns: minmax(0,1fr); }
}
@media (max-width: 440px) {
  .site-header { padding-inline: 20px; }
  .brand { font-size: 21px; }
  .brand small { margin-left: 6px; font-size: 9px; }
  .brand-mark { width: 25px; height: 25px; flex-shrink: 0; }
  .primary-nav a { font-size: 11px; }
  .primary-nav { gap: 18px; justify-content: flex-start; }
  .hero { padding-top: 42px; padding-bottom: 40px; }
  h1 { font-size: 38px; letter-spacing: -.04em; }
  .eyebrow { font-size: 10px; }
  .hero-description { font-size: 16px; }
  .hero-cinema img { border-radius: 16px; }
  .hero-cinema figcaption { text-align: left; font-size: 10px; }
  .hero-demo { padding: 20px; }
  .aperture-ring { width: 90px; height: 90px; }
  .aperture-comparison { gap: 18px; padding: 36px 0 28px; }
  .aperture-open { width: 56px; height: 56px; }
  .aperture-closed { width: 39.6px; height: 39.6px; }
  .demo-top { font-size: 9px; gap: 10px; }
  .learning-facts { padding-top: 22px; padding-bottom: 22px; flex-wrap: wrap; justify-content: flex-start; gap: 12px 20px; }
  .learning-facts span { font-size: 12px; }
  .learning-facts b { margin-right: 5px; }
  .cinema-intro { padding: 22px; border-radius: 22px; }
  .cinema-intro-copy p:not(.eyebrow) { font-size: 14px; }
  .lesson-content { padding: 26px 20px; border-radius: 22px; }
  .lesson-content h3 { font-size: 29px; }
  .lesson-body p, .guide-body p { font-size: 15px; line-height: 1.8; }
  .app-steps li, .limits-list li { font-size: 14px; }
  .lesson-experiment { padding: 20px; }
  .lesson-nav-link { font-size: 13px; }
  .glossary-grid, .sources-grid { grid-template-columns: minmax(0,1fr); }
  .guide-chapter > summary { font-size: 19px; }
  .guide-chapter > summary .chapter-number { margin-right: 10px; }
  .experiment-tabs { gap: 7px; border-radius: 18px; }
  .experiment-tabs button { font-size: 11px; padding: 11px 13px; }
  .site-footer nav { flex-wrap: wrap; gap: 20px; }
  .section-heading h2 { font-size: 32px; }
}
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } *, *::before, *::after { animation: none !important; transition: none !important; } }
@media print { :root { --bg: #fff; --panel: #fff; --text: #111; color-scheme: light; background: #fff; color: #111; } body { background: #fff; } body>*, main>* { display: none !important; } main, #guide { display: block !important; } .guide-toolbar,.section-heading>p,.guide-chapter>summary::marker { display: none !important; } #guide { padding: 0; margin: 0; max-width: none; } #guide h2 { font-size: 25pt; color: #111; } #guide .eyebrow { color: #444; } .guide-chapter { border-color: #bbb; break-inside: auto; } .guide-chapter>summary { color: #111; font-size: 14pt; padding-top: 22pt; padding-bottom: 12pt; list-style: none; } .guide-chapter>summary .chapter-number { color: #444; } .guide-chapter:not([open])>div { display: block !important; } .guide-body { max-width: none; margin-left: 0; } .guide-body p,.guide-body li { color: #222; font-size: 10pt; line-height: 1.6; } .guide-body h3 { color: #111; font-size: 12pt; break-after: avoid; } .print-appendix { display: block; break-before: page; } .print-appendix h3 { font-size: 18pt; } .print-appendix dt { font-size: 11pt; font-weight: 600; margin: 15pt 0 5pt; } .print-appendix dd { font-size: 10pt; line-height: 1.5; margin: 0; } .print-appendix li { font-size: 10pt; line-height: 1.6; margin-bottom: 14pt; } .print-appendix a { color: #333; overflow-wrap: anywhere; } @page { size: A4; margin: 18mm; } }