:root {
  --paper: #f5f7f8;
  --white: #ffffff;
  --ink: #17202a;
  --text: #35424b;
  --muted: #697780;
  --line: #d7dfe3;
  --red: #c53b24;
  --blue: #2d65d4;
  --navy: #131d27;
  --shell: min(1180px, calc(100vw - 64px));
  --serif: 'Songti SC', 'STSong', 'Iowan Old Style', Georgia, serif;
  --sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 86px; }
body { margin: 0; overflow-x: hidden; color: var(--ink); background: var(--paper); font-family: var(--sans); -webkit-font-smoothing: antialiased; }
img { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button, a { -webkit-tap-highlight-color: transparent; }
.section-shell { width: var(--shell); margin-inline: auto; }
.skip-link { position: fixed; z-index: 100; top: 10px; left: 10px; padding: 10px 14px; transform: translateY(-150%); background: var(--ink); color: white; border-radius: 4px; }
.skip-link:focus { transform: none; }

.site-header { position: sticky; z-index: 50; top: 0; height: 74px; border-bottom: 1px solid transparent; transition: background .25s ease, border-color .25s ease, box-shadow .25s ease; }
.site-header.scrolled { border-color: rgba(23,32,42,.1); background: rgba(245,247,248,.86); box-shadow: 0 8px 30px rgba(22,36,47,.04); backdrop-filter: blur(18px); }
.nav-shell { width: var(--shell); height: 100%; margin: auto; display: flex; align-items: center; gap: 48px; }
.brand { display: inline-flex; align-items: center; gap: 9px; flex: none; }
.brand img { border-radius: 8px; }
.brand span, .footer-brand > span { font: 700 25px/1 var(--serif); letter-spacing: 2px; }
.brand i, .footer-brand i { color: var(--red); font-style: normal; }
.nav-links { display: flex; align-items: center; gap: 30px; margin-left: auto; font-size: 13px; color: #53616a; }
.nav-links a { position: relative; padding: 10px 0; }
.nav-links a::after { content: ''; position: absolute; left: 0; right: 100%; bottom: 3px; height: 1px; background: var(--red); transition: right .22s ease; }
.nav-links a:hover::after { right: 0; }
.nav-download { margin-left: 8px; padding: 11px 17px; border: 1px solid #bfc9ce; border-radius: 7px; background: rgba(255,255,255,.7); font-size: 13px; font-weight: 650; transition: transform .2s ease, border-color .2s ease, box-shadow .2s ease; }
.nav-download:hover { transform: translateY(-1px); border-color: var(--ink); box-shadow: 0 6px 18px rgba(23,32,42,.08); }

.hero { min-height: 670px; padding: 108px 0 92px; display: grid; grid-template-columns: minmax(0, 820px) 250px; align-items: end; justify-content: space-between; gap: 64px; }
.eyebrow { margin: 0 0 24px; color: var(--red); font-size: 12px; line-height: 1; font-weight: 750; letter-spacing: 1.7px; text-transform: uppercase; }
.eyebrow span { display: inline-block; width: 36px; margin-right: 10px; border-top: 1px solid currentColor; vertical-align: 4px; }
.hero h1 { max-width: 850px; margin: 0; font: 700 clamp(52px, 5.8vw, 79px)/1.08 var(--serif); letter-spacing: -3.2px; }
.hero h1 em { color: var(--red); font-style: normal; }
.hero-lead { max-width: 690px; margin: 32px 0 0; color: var(--text); font: 19px/1.85 var(--sans); }
.hero-actions { display: flex; align-items: center; gap: 28px; margin-top: 35px; }
.primary-cta { min-height: 52px; padding: 0 23px; display: inline-flex; align-items: center; justify-content: center; gap: 11px; border-radius: 7px; background: var(--red); color: white; font-size: 15px; font-weight: 700; box-shadow: 0 11px 28px rgba(197,59,36,.19); transition: transform .2s ease, background .2s ease, box-shadow .2s ease; }
.primary-cta svg { width: 22px; height: 22px; }
.primary-cta:hover { transform: translateY(-2px); background: #ae301c; box-shadow: 0 15px 34px rgba(197,59,36,.25); }
.text-link { padding: 12px 0; border-bottom: 1px solid #abb7bd; color: var(--text); font-size: 14px; }
.microcopy { margin: 17px 0 0; color: #7a878f; font-size: 12px; }
.hero-note { align-self: center; padding: 21px 0 8px 24px; border-left: 3px solid var(--red); }
.hero-note strong { display: block; margin-bottom: 17px; font: 700 20px/1.3 var(--serif); }
.hero-note span { display: block; padding: 7px 0; border-bottom: 1px solid var(--line); color: var(--muted); font-size: 13px; }

.product-stage { overflow: hidden; border: 1px solid #cbd4d9; border-radius: 13px; background: white; box-shadow: 0 36px 90px rgba(24,41,52,.16); }
.stage-bar { height: 48px; padding: 0 17px; display: flex; align-items: center; justify-content: space-between; border-bottom: 1px solid #dfe5e8; background: #f9fafb; color: #7b878e; font-size: 11px; letter-spacing: .8px; }
.window-dots { display: flex; gap: 7px; }
.window-dots i { width: 8px; height: 8px; border-radius: 50%; background: #c7d0d5; }
.window-dots i:first-child { background: var(--red); }
.product-stage > img { width: 100%; height: auto; }
.understage { padding: 44px 0 136px; display: grid; grid-template-columns: repeat(3, 1fr); border-bottom: 1px solid var(--line); }
.under-item { padding: 0 34px; border-left: 1px solid var(--line); }
.under-item:first-child { padding-left: 0; border-left: 0; }
.under-item b { display: block; margin-bottom: 18px; color: var(--red); font: 700 11px/1 var(--sans); letter-spacing: 1px; }
.under-item span { font: 700 20px/1.2 var(--serif); }
.under-item p { max-width: 280px; margin: 10px 0 0; color: var(--muted); font-size: 13px; line-height: 1.7; }

.how { padding: 148px 0; display: grid; grid-template-columns: minmax(0, 1fr) minmax(430px, .9fr); gap: 120px; align-items: start; }
.section-heading { position: sticky; top: 130px; }
.section-heading h2, .wordbook-copy h2, .choice-title h2, .final-cta h2 { margin: 0; font: 700 clamp(42px, 4.4vw, 64px)/1.12 var(--serif); letter-spacing: -2px; }
.section-heading > p:last-child, .wordbook-copy > p { max-width: 510px; margin: 28px 0 0; color: var(--muted); font-size: 16px; line-height: 1.9; }
.meaning-stack { border-top: 1px solid #bfc9ce; }
.meaning-card { min-height: 174px; padding: 34px 0; display: grid; grid-template-columns: 58px 1fr; gap: 19px; border-bottom: 1px solid #bfc9ce; }
.meaning-no { width: 38px; height: 38px; display: grid; place-items: center; border: 1px solid var(--red); border-radius: 50%; color: var(--red); font: 700 13px/1 Georgia, serif; }
.meaning-card h3 { margin: 3px 0 10px; font: 700 24px/1.2 var(--serif); }
.meaning-card p { margin: 0; color: var(--muted); font-size: 14px; line-height: 1.75; }

.wordbook { padding: 50px 0 150px; display: grid; grid-template-columns: 400px minmax(0, 1fr); gap: 90px; align-items: center; }
.wordbook-copy ul { margin: 31px 0 0; padding: 0; list-style: none; }
.wordbook-copy li { padding: 13px 0 13px 23px; position: relative; border-bottom: 1px solid var(--line); color: var(--text); font-size: 13px; line-height: 1.5; }
.wordbook-copy li::before { content: '、'; position: absolute; left: 0; color: var(--red); font-weight: 800; }
.wordbook-visual { width: min(100%, 560px); justify-self: end; margin: 0; padding: 18px 18px 0; overflow: hidden; border: 1px solid #c2cdd3; border-radius: 20px; background: linear-gradient(145deg, #dbe4e8, #edf2f4); box-shadow: 0 30px 80px rgba(28,44,56,.16); }
.wordbook-visual img { width: 100%; height: auto; border: 1px solid #ded4c4; border-radius: 13px 13px 0 0; background: #fbf8f1; box-shadow: 0 18px 45px rgba(39,45,48,.13); }
.wordbook-visual figcaption { padding: 14px 2px 15px; color: #65737b; font-size: 11px; letter-spacing: .8px; }

.gallery { padding: 0 0 150px; display: grid; grid-template-columns: 1fr 1fr; gap: 28px; align-items: start; }
.gallery-hint { display: none; }
.gallery-card { margin: 0; padding: 22px 22px 0; overflow: hidden; border: 1px solid #c6d0d5; border-radius: 18px; background: linear-gradient(145deg, #dce5e9, #eef2f4); }
.gallery-card img { width: 100%; height: auto; border: 1px solid #ded4c4; border-radius: 11px 11px 0 0; background: #fbf8f1; box-shadow: 0 17px 42px rgba(39,45,48,.12); }
.gallery-card figcaption { padding: 24px 26px 26px; display: flex; flex-direction: column; gap: 7px; }
.gallery-card figcaption b { font: 700 21px/1.2 var(--serif); }
.gallery-card figcaption span { color: var(--muted); font-size: 13px; }

.choice { padding: 140px 0; color: #f4f7f8; background: var(--navy); }
.choice-inner { display: grid; grid-template-columns: 350px minmax(0, 1fr); gap: 85px; }
.eyebrow.light { color: #ef745d; }
.choice-grid { display: grid; grid-template-columns: repeat(3, 1fr); border-top: 1px solid #41505d; }
.choice-card { min-height: 360px; padding: 29px 25px; border-right: 1px solid #41505d; border-bottom: 1px solid #41505d; }
.choice-card:first-child { border-left: 1px solid #41505d; }
.choice-card > span { color: #ef745d; font-size: 11px; font-weight: 750; letter-spacing: 1px; }
.choice-card h3 { margin: 42px 0 16px; font: 700 23px/1.35 var(--serif); }
.choice-card p { margin: 0; color: #aeb9c1; font-size: 13px; line-height: 1.85; }
.choice-card i, .choice-card a { display: block; margin-top: 50px; color: #d9e0e4; font-size: 12px; font-style: normal; }
.choice-card a { color: #ef745d; }

.faq { padding: 150px 0 130px; display: grid; grid-template-columns: 380px 1fr; gap: 100px; }
.section-heading.compact { position: static; }
.faq-list { border-top: 1px solid #bfc9ce; }
.faq-list details { border-bottom: 1px solid #bfc9ce; }
.faq-list summary { min-height: 78px; padding: 22px 45px 22px 0; position: relative; display: flex; align-items: center; cursor: pointer; list-style: none; font: 700 18px/1.4 var(--serif); }
.faq-list summary::-webkit-details-marker { display: none; }
.faq-list summary i, .faq-list summary i::after { position: absolute; right: 4px; width: 16px; height: 1px; background: var(--red); content: ''; transition: transform .2s ease; }
.faq-list summary i::after { right: 0; transform: rotate(90deg); }
.faq-list details[open] summary i::after { transform: rotate(0); }
.faq-list details p { max-width: 660px; margin: -4px 0 25px; color: var(--muted); font-size: 14px; line-height: 1.85; }

.final-cta { margin-bottom: 130px; padding: 88px 70px; position: relative; overflow: hidden; text-align: center; border-radius: 12px; background: white; box-shadow: 0 26px 75px rgba(28,44,56,.09); }
.final-cta::before { content: 'context'; position: absolute; left: -20px; top: -77px; color: rgba(45,101,212,.045); font: 700 190px/1 Georgia, serif; pointer-events: none; }
.final-cta img { margin: 0 auto 24px; border-radius: 17px; box-shadow: 0 12px 25px rgba(23,32,42,.13); }
.final-cta p { margin: 0 0 13px; color: var(--muted); font-size: 14px; }
.final-cta h2 { max-width: 750px; margin-inline: auto; font-size: clamp(36px, 4vw, 56px); }
.final-cta .primary-cta { margin-top: 33px; }

.site-footer { border-top: 1px solid var(--line); background: #edf1f3; }
.footer-inner { min-height: 210px; padding: 45px 0 34px; display: grid; grid-template-columns: 1fr auto; align-items: start; gap: 32px; }
.footer-brand p { margin: 11px 0 0; color: var(--muted); font-size: 12px; }
.footer-links { display: flex; flex-wrap: wrap; justify-content: flex-end; gap: 24px; color: #56646d; font-size: 12px; }
.footer-links a:hover { color: var(--red); }
.footer-inner small { grid-column: 1/-1; align-self: end; color: #87939a; font-size: 11px; }

.js .reveal { opacity: 0; transform: translateY(20px); transition: opacity .7s cubic-bezier(.22,1,.36,1), transform .7s cubic-bezier(.22,1,.36,1); }
.js .reveal.visible { opacity: 1; transform: none; }
a:focus-visible, summary:focus-visible { outline: 2px solid var(--blue); outline-offset: 4px; border-radius: 3px; }

@media (max-width: 980px) {
  :root { --shell: min(100% - 40px, 760px); }
  .nav-links { display: none; }
  .nav-download { margin-left: auto; }
  .hero { min-height: auto; padding: 90px 0 70px; grid-template-columns: 1fr; gap: 50px; }
  .hero h1 { font-size: clamp(49px, 8vw, 70px); }
  .hero-note { max-width: 300px; }
  .how { padding: 110px 0; grid-template-columns: 1fr; gap: 65px; }
  .section-heading { position: static; }
  .wordbook { grid-template-columns: 1fr; gap: 50px; padding-bottom: 110px; }
  .wordbook-copy { max-width: 540px; }
  .choice-inner { grid-template-columns: 1fr; gap: 62px; }
  .choice-title { max-width: 600px; }
  .choice-grid { grid-template-columns: 1fr; }
  .choice-card { min-height: 0; border-left: 1px solid #41505d; }
  .choice-card h3 { margin-top: 25px; }
  .choice-card i, .choice-card a { margin-top: 25px; }
  .faq { grid-template-columns: 1fr; gap: 60px; }
}

@media (max-width: 640px) {
  :root { --shell: calc(100vw - 30px); }
  .site-header { height: 66px; }
  .nav-shell { gap: 12px; }
  .brand img { width: 30px; height: 30px; }
  .brand span { font-size: 21px; }
  .nav-download { width: 70px; min-height: 37px; padding: 0; display: grid; place-items: center; font-size: 0; }
  .nav-download::before { content: '安装 ↗'; font-size: 12px; }
  .hero { padding: 54px 0 42px; gap: 30px; }
  .hero h1 { font-size: clamp(39px, 11vw, 48px); line-height: 1.13; letter-spacing: -1.7px; }
  .hero h1 br { display: none; }
  .hero-lead { margin-top: 25px; font-size: 16px; line-height: 1.8; }
  .hero-actions { align-items: stretch; flex-direction: column; gap: 10px; }
  .text-link { align-self: flex-start; }
  .microcopy { line-height: 1.6; }
  .hero-note { max-width: none; padding: 0; display: grid; grid-template-columns: repeat(3, 1fr); border: 1px solid var(--line); border-left: 0; border-right: 0; }
  .hero-note strong { grid-column: 1 / -1; margin: 0; padding: 16px 2px 13px; font-size: 17px; }
  .hero-note span { padding: 11px 3px; text-align: center; border-bottom: 0; border-right: 1px solid var(--line); font-size: 11px; }
  .hero-note span:last-child { border-right: 0; }
  .product-stage { width: calc(100vw - 24px); border-radius: 9px; }
  .product-stage > img { width: 100%; height: 390px; max-width: 100%; object-fit: cover; object-position: 78% center; transform: none; }
  .stage-bar { height: 42px; }
  .understage { width: 100vw; margin-left: calc((100vw - var(--shell)) / -2); padding: 24px 15px 78px; display: flex; gap: 12px; overflow-x: auto; border-bottom: 0; scroll-snap-type: x mandatory; scrollbar-width: none; }
  .understage::-webkit-scrollbar { display: none; }
  .under-item, .under-item:first-child { flex: 0 0 76vw; min-height: 154px; padding: 22px; border: 1px solid var(--line); border-radius: 10px; background: rgba(255,255,255,.72); scroll-snap-align: center; }
  .under-item p { max-width: none; }
  .how { padding: 80px 0; gap: 44px; }
  .section-heading h2, .wordbook-copy h2, .choice-title h2 { font-size: 40px; letter-spacing: -1.2px; }
  .section-heading > p:last-child, .wordbook-copy > p { margin-top: 21px; font-size: 15px; line-height: 1.8; }
  .meaning-card { min-height: 0; grid-template-columns: 46px 1fr; }
  .wordbook { padding: 8px 0 80px; gap: 37px; }
  .wordbook-visual { width: min(100%, 520px); justify-self: center; padding: 10px 10px 0; border-radius: 13px; }
  .gallery { width: 100vw; margin-left: calc((100vw - var(--shell)) / -2); padding: 42px 15px 88px; position: relative; display: flex; gap: 14px; overflow-x: auto; scroll-snap-type: x mandatory; scrollbar-width: none; }
  .gallery::-webkit-scrollbar { display: none; }
  .gallery-hint { position: absolute; top: 0; left: 30px; display: block; margin: 0; color: var(--muted); font-size: 12px; }
  .gallery-card { flex: 0 0 86vw; padding: 10px 10px 0; border-radius: 13px; scroll-snap-align: center; }
  .gallery-card figcaption { padding: 20px 12px 22px; }
  .choice { padding: 80px 0; }
  .choice-inner { gap: 45px; }
  .choice-card { padding: 27px 22px; }
  .faq { padding: 82px 0 75px; gap: 38px; }
  .final-cta { margin-bottom: 75px; padding: 56px 20px; }
  .final-cta h2 { font-size: 36px; }
  .footer-inner { grid-template-columns: 1fr; }
  .footer-links { justify-content: flex-start; gap: 18px; }
  .footer-inner small { grid-column: auto; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { scroll-behavior: auto !important; transition-duration: .01ms !important; animation-duration: .01ms !important; animation-iteration-count: 1 !important; }
  .reveal { opacity: 1; transform: none; }
}