:root {
  --ink: #111111;
  --paper: #f5f5f0;
  --white: #ffffff;
  --blue: #075cff;
  --yellow: #ffd400;
  --red: #ff4b3e;
  --line: #c9c9c2;
  --muted: #65655f;
  --max: 1280px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: Inter, system-ui, -apple-system, BlinkMacSystemFont, "PingFang TC", "Noto Sans TC", sans-serif;
  letter-spacing: 0;
}
img { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button, summary { font: inherit; }
section[id] { scroll-margin-top: 86px; }

.site-header {
  position: sticky;
  z-index: 20;
  top: 0;
  min-height: 68px;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  border-bottom: 1px solid #2a2a2a;
  color: var(--white);
  background: var(--ink);
}
.brand, .header-buy, .site-header nav { height: 68px; display: flex; align-items: center; }
.brand { gap: 12px; padding: 0 28px; font-weight: 750; }
.brand-mark { display: inline-flex; gap: 3px; }
.brand-mark i { width: 5px; height: 15px; display: block; background: var(--yellow); }
.site-header nav a { padding: 23px 18px; color: #d0d0cc; font-size: 14px; }
.site-header nav a:hover, .site-header nav a:focus-visible { color: var(--yellow); }
.header-buy { justify-self: end; min-width: 160px; justify-content: center; background: var(--yellow); color: var(--ink); font-weight: 800; }

.product-intro { background: var(--ink); color: var(--white); overflow: hidden; }
.intro-copy { max-width: var(--max); margin: 0 auto; padding: 64px 44px 34px; }
.eyebrow, .section-number { margin: 0 0 22px; color: var(--blue); font-size: 13px; font-weight: 800; text-transform: uppercase; }
.eyebrow { color: var(--yellow); }
h1, h2, h3, p { letter-spacing: 0; }
h1 { max-width: 840px; margin: 0; font-size: 72px; line-height: 1.02; font-weight: 800; }
.lead { max-width: 760px; margin: 28px 0 0; color: #c9c9c3; font-size: 20px; line-height: 1.7; }
.buy-line { margin-top: 36px; display: flex; align-items: stretch; justify-content: space-between; gap: 32px; border-top: 1px solid #393939; border-bottom: 1px solid #393939; }
.buy-line > div { display: flex; align-items: baseline; gap: 16px; padding: 24px 0; }
.buy-line strong { font-size: 30px; }
.buy-line span { color: #a9a9a4; font-size: 13px; }
.primary-action { min-width: 240px; display: inline-flex; align-items: center; justify-content: space-between; gap: 24px; padding: 18px 22px; background: var(--yellow); color: var(--ink); font-weight: 800; }
.primary-action:hover, .primary-action:focus-visible { background: var(--white); }
.hero-product { max-width: 1440px; margin: 0 auto; padding: 0 22px; }
.hero-product img { width: 100%; height: 320px; object-fit: cover; object-position: top; border: 1px solid #373737; }
.section-cue { width: max-content; margin: 22px auto 0; padding: 12px 18px 28px; display: block; color: #bfbfba; font-size: 13px; }

.system-overview, .fit-section, .faq-section { max-width: var(--max); margin: 0 auto; padding: 112px 44px; }
.section-heading { display: grid; grid-template-columns: 1fr 2fr; gap: 32px; align-items: start; margin-bottom: 56px; }
.section-heading h2, .fit-copy h2, .closing-buy h2 { margin: 0; font-size: 48px; line-height: 1.16; font-weight: 760; }
.preview-switcher { border-top: 1px solid var(--ink); }
.preview-tabs { display: grid; grid-template-columns: repeat(5, 1fr); border-bottom: 1px solid var(--ink); }
.preview-tabs button { min-height: 56px; border: 0; border-right: 1px solid var(--ink); padding: 10px 14px; background: transparent; color: var(--ink); cursor: pointer; }
.preview-tabs button:last-child { border-right: 0; }
.preview-tabs button[aria-selected="true"] { background: var(--blue); color: var(--white); }
.preview-tabs button:focus-visible { outline: 3px solid var(--red); outline-offset: -3px; }
.preview-stage { margin: 0; padding: 32px 0 0; }
.preview-stage img { width: 100%; aspect-ratio: 16 / 9; object-fit: contain; object-position: top; background: var(--white); border: 1px solid var(--line); }
.preview-stage figcaption { display: grid; grid-template-columns: 80px 1fr; gap: 24px; border-bottom: 1px solid var(--ink); padding: 22px 0 30px; }
.preview-stage figcaption span { color: var(--blue); font-size: 22px; font-weight: 800; }
.preview-stage figcaption p { max-width: 720px; margin: 0; color: var(--muted); line-height: 1.7; }
.sheet-list { margin: 56px 0 0; padding: 0; display: grid; grid-template-columns: repeat(3, 1fr); list-style: none; border-top: 1px solid var(--ink); }
.sheet-list li { min-height: 64px; display: grid; grid-template-columns: 42px 1fr; align-items: center; border-bottom: 1px solid var(--line); padding: 0 12px; }
.sheet-list li:nth-child(3n+2), .sheet-list li:nth-child(3n+3) { border-left: 1px solid var(--line); }
.sheet-list span { color: var(--blue); font-size: 12px; font-weight: 800; }

.fit-section { display: grid; grid-template-columns: 1fr 1.45fr; gap: 80px; border-top: 1px solid var(--ink); }
.fit-copy { position: sticky; top: 104px; align-self: start; }
.fit-grid { border-top: 1px solid var(--ink); }
.fit-grid article { display: grid; grid-template-columns: 48px 180px 1fr; align-items: baseline; gap: 20px; padding: 28px 0; border-bottom: 1px solid var(--line); }
.fit-grid article > span { color: var(--blue); font-size: 13px; font-weight: 800; }
.fit-grid h3 { margin: 0; font-size: 19px; }
.fit-grid p { margin: 0; color: var(--muted); line-height: 1.65; }

.deliverables { padding: 104px max(44px, calc((100vw - var(--max)) / 2 + 44px)); background: var(--ink); color: var(--white); }
.section-heading.inverse { max-width: var(--max); margin-left: auto; margin-right: auto; }
.deliverable-table { max-width: var(--max); margin: 0 auto; border-top: 1px solid #555; }
.deliverable-table > div { min-height: 80px; display: grid; grid-template-columns: 70px 1.2fr 1.6fr 80px; gap: 20px; align-items: center; border-bottom: 1px solid #3c3c3c; }
.deliverable-table > div > span:first-child { color: var(--yellow); font-weight: 800; }
.deliverable-table strong { font-size: 20px; }
.deliverable-table > div > span:nth-child(3) { color: #bdbdb8; }
.deliverable-table b { color: var(--blue); font-size: 13px; }
.compatibility { max-width: var(--max); margin: 42px auto 0; display: grid; grid-template-columns: 170px 1fr; gap: 28px; padding: 24px; background: var(--yellow); color: var(--ink); }
.compatibility p { margin: 0; line-height: 1.6; }

.free-tool { max-width: var(--max); margin: 0 auto; display: grid; grid-template-columns: 2fr 1fr; align-items: end; gap: 70px; padding: 100px 44px; border-bottom: 1px solid var(--ink); }
.free-tool h2 { margin: 0; font-size: 48px; line-height: 1.12; }
.free-tool p:not(.section-number) { max-width: 620px; margin: 24px 0 0; color: var(--muted); font-size: 17px; line-height: 1.7; }
.download-action { min-height: 84px; display: flex; align-items: center; justify-content: space-between; gap: 20px; padding: 22px 24px; background: var(--yellow); font-size: 18px; font-weight: 800; }
.download-action:hover, .download-action:focus-visible { background: var(--blue); color: var(--white); }

.faq-section { display: grid; grid-template-columns: 1fr 2fr; gap: 70px; }
.faq-section .section-heading { display: block; margin: 0; }
.faq-list { border-top: 1px solid var(--ink); }
.faq-list details { border-bottom: 1px solid var(--line); }
.faq-list summary { position: relative; cursor: pointer; list-style: none; padding: 25px 44px 25px 0; font-size: 18px; font-weight: 700; }
.faq-list summary::-webkit-details-marker { display: none; }
.faq-list summary::after { content: "+"; position: absolute; right: 4px; top: 20px; color: var(--blue); font-size: 28px; font-weight: 400; }
.faq-list details[open] summary::after { content: "−"; }
.faq-list details p { margin: 0; padding: 0 44px 26px 0; color: var(--muted); line-height: 1.7; }

.closing-buy { padding: 104px max(44px, calc((100vw - var(--max)) / 2 + 44px)); background: var(--blue); color: var(--white); }
.closing-buy .section-number { color: var(--yellow); }
.closing-buy h2 { max-width: var(--max); font-size: 58px; }
.early-access { max-width: var(--max); margin-top: 58px; display: grid; grid-template-columns: minmax(220px, .75fr) minmax(420px, 1.25fr); gap: 54px; align-items: center; border-top: 1px solid rgba(255,255,255,.45); border-bottom: 1px solid rgba(255,255,255,.45); padding: 28px 0; }
.early-access > div { display: grid; gap: 7px; }
.early-access strong { font-size: 32px; }
.early-access > div span { color: #d8e4ff; font-size: 13px; }
.early-access form { display: grid; gap: 9px; }
.early-access label { font-size: 13px; font-weight: 750; }
.early-access-fields { display: grid; grid-template-columns: minmax(0, 1fr) auto; }
.early-access input[type="email"] { min-width: 0; min-height: 54px; border: 1px solid var(--white); border-radius: 0; padding: 0 16px; background: var(--white); color: var(--ink); font: inherit; }
.early-access button { min-width: 150px; border: 1px solid var(--yellow); border-radius: 0; padding: 0 18px; display: flex; align-items: center; justify-content: space-between; gap: 20px; background: var(--yellow); color: var(--ink); font: inherit; font-weight: 800; cursor: pointer; }
.early-access button:hover, .early-access button:focus-visible { background: var(--white); border-color: var(--white); }
.early-access small { color: #d8e4ff; font-size: 11px; }
.form-honey { position: absolute; left: -9999px; width: 1px; height: 1px; opacity: 0; pointer-events: none; }
.primary-action.light { background: var(--white); }
.primary-action.light:hover, .primary-action.light:focus-visible { background: var(--yellow); }

footer { min-height: 180px; display: grid; grid-template-columns: 1fr 1fr auto; align-items: end; gap: 30px; padding: 52px max(28px, calc((100vw - var(--max)) / 2 + 44px)); background: var(--ink); color: var(--white); }
.footer-brand { display: flex; gap: 12px; align-items: center; }
footer p { margin: 0; color: #aaa; font-size: 13px; }
footer p a { display: inline-block; margin-top: 8px; color: var(--yellow); }
footer > span { color: #777; font-size: 11px; }

.guide-page { background: var(--paper); }
.guide-hero { padding: 86px max(44px, calc((100vw - 1080px) / 2)); border-bottom: 1px solid var(--ink); }
.guide-hero h1 { max-width: 980px; font-size: 58px; color: var(--ink); }
.guide-hero .lead { color: var(--muted); }
.guide-meta { margin-top: 30px; display: flex; gap: 24px; color: var(--muted); font-size: 13px; }
.guide-visual { max-width: 1180px; margin: 0 auto; padding: 0 44px; transform: translateY(44px); }
.guide-visual img { width: 100%; border: 1px solid var(--line); background: var(--white); }
.guide-body { max-width: 1080px; margin: 44px auto 0; display: grid; grid-template-columns: 260px 1fr; gap: 80px; padding: 96px 44px 112px; }
.guide-toc { position: sticky; top: 100px; align-self: start; border-top: 1px solid var(--ink); }
.guide-toc strong { display: block; padding: 18px 0; font-size: 13px; }
.guide-toc a { display: block; padding: 10px 0; border-top: 1px solid var(--line); color: var(--muted); font-size: 13px; }
.guide-toc a:hover, .guide-toc a:focus-visible { color: var(--blue); }
.guide-article section { scroll-margin-top: 95px; margin-bottom: 80px; }
.guide-article h2 { margin: 0 0 24px; font-size: 34px; line-height: 1.2; }
.guide-article h3 { margin: 38px 0 13px; font-size: 21px; }
.guide-article p, .guide-article li { color: #41413d; font-size: 17px; line-height: 1.85; }
.guide-article ul, .guide-article ol { padding-left: 23px; }
.guide-rule { margin: 30px 0; padding: 22px 24px; border-left: 7px solid var(--yellow); background: var(--white); font-weight: 700; }
.guide-table { width: 100%; border-collapse: collapse; margin: 26px 0 34px; background: var(--white); }
.guide-table th, .guide-table td { padding: 15px 13px; border: 1px solid var(--line); text-align: left; vertical-align: top; }
.guide-table th { background: var(--blue); color: var(--white); font-size: 13px; }
.guide-table td { color: #41413d; line-height: 1.55; }
.guide-cta { margin-top: 70px; padding: 34px; background: var(--ink); color: var(--white); }
.guide-cta h2 { color: var(--white); }
.guide-cta p { color: #c3c3be; }
.guide-actions { display: flex; gap: 12px; margin-top: 24px; }
.guide-actions a { padding: 16px 20px; background: var(--yellow); color: var(--ink); font-weight: 800; }
.guide-actions a.secondary { background: var(--blue); color: var(--white); }

.notes-index { max-width: var(--max); margin: 0 auto; padding: 82px 44px 112px; }
.notes-intro { max-width: 850px; }
.notes-intro h1 { color: var(--ink); font-size: 58px; }
.guide-hero .eyebrow, .notes-intro .eyebrow { color: var(--blue); }
.notes-intro .lead { color: var(--muted); }
.notes-grid { margin-top: 70px; display: grid; grid-template-columns: repeat(3, 1fr); border-top: 1px solid var(--ink); }
.note-card { min-height: 330px; display: flex; flex-direction: column; padding: 28px 24px 24px; border-bottom: 1px solid var(--ink); }
.note-card + .note-card { border-left: 1px solid var(--ink); }
.note-card .section-number { margin-bottom: 36px; }
.note-card h2 { margin: 0; font-size: 27px; line-height: 1.28; }
.note-card p { margin: 18px 0 26px; color: var(--muted); line-height: 1.7; }
.note-card a { margin-top: auto; display: flex; justify-content: space-between; gap: 20px; padding-top: 18px; border-top: 1px solid var(--line); color: var(--blue); font-weight: 800; }
.note-card:hover { background: var(--white); }
.article-source { margin-top: 32px; padding-top: 18px; border-top: 1px solid var(--line); color: var(--muted); font-size: 13px; }
.article-source a { color: var(--blue); text-decoration: underline; text-underline-offset: 3px; }

.not-found {
  min-height: 100vh;
  display: grid;
  place-content: center;
  justify-items: start;
  gap: 18px;
  padding: 48px;
  background: var(--paper);
}
.not-found h1 { max-width: 760px; margin: 0; font-size: 64px; line-height: 1.02; }
.not-found p { margin: 0; color: var(--muted); font-size: 18px; }
.not-found .primary-action { margin-top: 12px; }

@media (max-width: 900px) {
  .site-header { grid-template-columns: 1fr auto; }
  .site-header nav { display: none; }
  .header-buy { min-width: 120px; }
  .intro-copy, .system-overview, .fit-section, .faq-section { padding-left: 24px; padding-right: 24px; }
  h1 { font-size: 58px; }
  .section-heading, .faq-section, .free-tool, .early-access { grid-template-columns: 1fr; }
  .section-heading { gap: 10px; }
  .fit-section { grid-template-columns: 1fr; gap: 50px; }
  .fit-copy { position: static; }
  .deliverables, .closing-buy { padding-left: 24px; padding-right: 24px; }
  .free-tool { padding-left: 24px; padding-right: 24px; }
  .sheet-list { grid-template-columns: repeat(2, 1fr); }
  .sheet-list li:nth-child(3n+2), .sheet-list li:nth-child(3n+3) { border-left: 0; }
  .sheet-list li:nth-child(even) { border-left: 1px solid var(--line); }
  .guide-body { grid-template-columns: 1fr; gap: 40px; }
  .guide-toc { position: static; }
  .notes-grid { grid-template-columns: 1fr; }
  .note-card + .note-card { border-left: 0; }
}

@media (max-width: 620px) {
  .brand { padding: 0 16px; }
  .brand > span:last-child { font-size: 14px; }
  .header-buy { min-width: 104px; font-size: 14px; }
  .product-intro { min-height: auto; }
  .intro-copy { padding-top: 38px; padding-bottom: 24px; }
  h1 { font-size: 43px; line-height: 1.08; }
  .lead { margin-top: 22px; font-size: 16px; }
  .buy-line { margin-top: 28px; }
  .buy-line > div { padding: 18px 0; }
  .buy-line { display: block; }
  .buy-line > div { display: grid; gap: 5px; }
  .early-access { gap: 24px; }
  .early-access-fields { grid-template-columns: 1fr; gap: 8px; }
  .early-access button { min-height: 54px; }
  .primary-action { width: 100%; min-width: 0; }
  .hero-product { padding: 0 12px; }
  .hero-product img { height: 150px; object-fit: cover; object-position: left top; }
  .section-cue { margin-top: 12px; padding-bottom: 18px; }
  .system-overview, .fit-section, .faq-section { padding-top: 80px; padding-bottom: 80px; }
  .section-heading h2, .fit-copy h2, .closing-buy h2, .free-tool h2 { font-size: 34px; }
  .preview-tabs { grid-template-columns: repeat(5, minmax(88px, 1fr)); overflow-x: auto; }
  .preview-tabs button { white-space: nowrap; }
  .preview-stage img { aspect-ratio: 4 / 3; object-fit: cover; object-position: left top; }
  .preview-stage figcaption { grid-template-columns: 42px 1fr; }
  .sheet-list { grid-template-columns: 1fr; }
  .sheet-list li:nth-child(even) { border-left: 0; }
  .fit-grid article { grid-template-columns: 38px 1fr; }
  .fit-grid article p { grid-column: 2; }
  .deliverable-table > div { grid-template-columns: 42px 1fr 55px; padding: 20px 0; }
  .deliverable-table > div > span:nth-child(3) { grid-column: 2 / 4; }
  .compatibility { grid-template-columns: 1fr; }
  footer { grid-template-columns: 1fr; align-items: start; }
  .guide-hero { padding: 54px 24px; }
  .guide-hero h1 { font-size: 40px; }
  .guide-meta { display: grid; gap: 7px; }
  .guide-visual { padding: 0 12px; transform: translateY(24px); }
  .guide-body { margin-top: 24px; padding: 70px 24px 90px; }
  .guide-article h2 { font-size: 29px; }
  .guide-article p, .guide-article li { font-size: 16px; }
  .guide-table { font-size: 13px; }
  .guide-table th, .guide-table td { padding: 11px 9px; }
  .guide-actions { display: grid; }
  .notes-index { padding: 58px 24px 90px; }
  .notes-intro h1 { font-size: 42px; }
  .note-card { min-height: 0; padding: 26px 0; }
  .not-found { padding: 28px 20px; }
  .not-found h1 { font-size: 42px; }
}


@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}