:root {
  color: #1c1c1c;
  background: #f9f8f6;
  font-family: "Noto Sans CJK SC", "Microsoft YaHei", "PingFang SC", sans-serif;
  font-synthesis: none;
  --paper: #f9f8f6;
  --ink: #1c1c1c;
  --ink-80: rgb(28 28 28 / 80%);
  --ink-60: rgb(28 28 28 / 60%);
  --ink-muted: rgb(28 28 28 / 62%);
  --ink-40: rgb(28 28 28 / 40%);
  --ink-16: rgb(28 28 28 / 16%);
  --ink-10: rgb(28 28 28 / 10%);
  --serif: Georgia, "Noto Serif CJK SC", "Songti SC", "STSong", serif;
  --sans: "Noto Sans CJK SC", "Microsoft YaHei", "PingFang SC", sans-serif;
  --page-pad: clamp(1.5rem, 5vw, 4.5rem);
  --section-y: clamp(7rem, 14vw, 12rem);
  --max-width: 90rem;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 6rem; }
body { margin: 0; background: var(--paper); color: var(--ink); }
body, button { font-family: var(--sans); }
img { display: block; max-width: 100%; height: auto; }
a { color: inherit; }
button, a { touch-action: manipulation; -webkit-tap-highlight-color: transparent; }
button { cursor: pointer; }
button:disabled { cursor: not-allowed; }

:focus-visible {
  outline: 1px solid currentColor;
  outline-offset: 5px;
}

::selection { color: var(--paper); background: var(--ink); }

.skip-link {
  position: fixed;
  top: 0;
  left: 1rem;
  z-index: 100;
  padding: 0.75rem 1rem;
  color: var(--paper);
  background: var(--ink);
  transform: translateY(-120%);
}

.skip-link:focus { transform: translateY(0); }

.site-header {
  position: fixed;
  inset: 0 0 auto;
  z-index: 50;
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: center;
  min-height: 5rem;
  padding: 0 var(--page-pad);
  border-bottom: 1px solid var(--ink-10);
  background: rgb(249 248 246 / 92%);
  backdrop-filter: blur(10px);
}

.wordmark {
  display: inline-flex;
  min-height: 2.75rem;
  align-items: center;
  width: max-content;
  font-family: var(--serif);
  font-size: 1.05rem;
  letter-spacing: 0.3em;
  text-decoration: none;
}

.site-nav { display: flex; align-items: center; gap: clamp(1.25rem, 3vw, 3rem); }
.site-nav a, .menu-toggle {
  font-size: 0.75rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  text-decoration: none;
}

.nav-cta {
  display: inline-flex;
  min-height: 2.75rem;
  align-items: center;
  gap: 1.5rem;
  padding: 0 1rem;
  color: var(--paper);
  background: var(--ink);
  transition: color 200ms ease, background 200ms ease;
}

.nav-cta:hover { color: var(--ink); background: var(--paper); outline: 1px solid var(--ink); outline-offset: -1px; }
.site-nav a[aria-current="location"] { font-weight: 600; }
.site-nav .hover-line[aria-current="location"]::after { transform: scaleX(1); }
.site-nav .nav-cta[aria-current="location"] { box-shadow: inset 0 -2px 0 var(--paper); }
.menu-toggle { display: none; min-width: 4.5rem; min-height: 2.75rem; border: 0; background: none; color: var(--ink); }

.section-shell {
  width: min(100%, var(--max-width));
  margin-inline: auto;
  padding: var(--section-y) var(--page-pad);
}

.ruled { border-top: 1px solid var(--ink-16); }
.label {
  margin: 0;
  color: var(--ink-muted);
  font-size: 0.75rem;
  letter-spacing: 0.2em;
  line-height: 1.6;
  text-transform: uppercase;
}

.label-light { color: rgb(249 248 246 / 62%); }

h1, h2, h3, p { text-wrap: pretty; }
h1, h2, h3 { font-family: var(--serif); font-weight: 400; }
h1 em, h2 em { color: var(--ink-60); font-weight: 400; }

.hero {
  position: relative;
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  align-items: center;
  min-height: 100svh;
  padding-top: clamp(8rem, 15vh, 12rem);
  overflow: hidden;
}

.hero-copy { position: relative; z-index: 2; grid-column: 1 / span 7; }
.hero h1 {
  margin: 2rem 0 0;
  font-size: clamp(4.25rem, 9.7vw, 9rem);
  letter-spacing: -0.065em;
  line-height: 0.86;
}
.hero h1 em { display: inline-block; font-size: 0.61em; letter-spacing: -0.055em; }
.hero-deck { max-width: 34rem; margin: 3rem 0 0; color: var(--ink-80); font-size: clamp(1rem, 1.25vw, 1.18rem); line-height: 1.9; }
.hero-actions { display: flex; align-items: center; gap: 2rem; margin-top: 3rem; }

.button {
  display: inline-flex;
  min-height: 3rem;
  align-items: center;
  justify-content: space-between;
  gap: 2.5rem;
  padding: 0.75rem 1.5rem;
  border: 1px solid var(--ink);
  border-radius: 0;
  font-size: 0.875rem;
  letter-spacing: 0.06em;
  text-decoration: none;
  transition: color 200ms ease, background 200ms ease, border-color 200ms ease;
}

.button-dark { color: var(--paper); background: var(--ink); }
.button-dark:hover { color: var(--ink); background: transparent; }
.button-disabled { width: 100%; margin-top: 2rem; color: var(--ink-40); background: transparent; border-color: var(--ink-16); }

.text-link { display: inline-flex; min-height: 2.75rem; align-items: center; padding-block: 0.5rem; font-size: 0.85rem; text-underline-offset: 0.5rem; }
.hover-line { position: relative; }
.hover-line::after {
  position: absolute;
  right: 0;
  bottom: -0.35rem;
  left: 0;
  height: 1px;
  background: currentColor;
  content: "";
  transform: scaleX(0);
  transform-origin: right;
  transition: transform 500ms ease;
}
.hover-line:hover::after, .hover-line:focus-visible::after { transform: scaleX(1); transform-origin: left; }

.hero-visual { grid-column: 9 / -1; margin: 2rem 0 0; }
.screen-frame { overflow: hidden; border: 1px solid currentColor; background: #fff; }
.screen-frame img { display: block; width: 100%; max-width: 100%; height: auto; transition: transform 1000ms ease; }
.hero-visual:hover img, .screen-card:hover img { transform: scale(1.025); }
.screen-frame-hero { width: min(100%, 22rem); margin-left: auto; }
figcaption { display: flex; justify-content: space-between; gap: 1rem; margin-top: 0.8rem; font-size: 0.64rem; letter-spacing: 0.16em; text-transform: uppercase; }
.hero-index { position: absolute; right: var(--page-pad); bottom: 2rem; color: var(--ink-muted); font: 0.65rem/1 var(--sans); letter-spacing: 0.2em; }

.philosophy, .features, .guide, .flash-section {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: clamp(3rem, 7vw, 7rem);
}
.section-heading { grid-column: 1 / span 6; }
.section-heading h2, .guide h2, .flash-heading h2, .interface-heading h2, .support-heading h2, .closing h2 {
  margin: 1.5rem 0 0;
  font-size: clamp(3.25rem, 6.7vw, 7.3rem);
  letter-spacing: -0.055em;
  line-height: 0.94;
}
.section-heading h2 em, .guide h2 em, .flash-heading h2 em, .closing h2 em { font-style: italic; }
.heading-line { display: inline-block; white-space: nowrap; }
.philosophy-body { grid-column: 8 / -1; align-self: end; max-width: 34rem; }
.philosophy-body > p { color: var(--ink-80); line-height: 1.9; }
.philosophy-body .standfirst { margin-top: 0; font-family: var(--serif); font-size: clamp(1.5rem, 2.3vw, 2.25rem); line-height: 1.45; }
.fact-list { margin: 3.5rem 0 0; border-top: 1px solid var(--ink-16); }
.fact-list div { display: grid; grid-template-columns: 1fr 2fr; gap: 1rem; padding: 1rem 0; border-bottom: 1px solid var(--ink-10); }
.fact-list dt { color: var(--ink-muted); font-size: 0.7rem; letter-spacing: 0.16em; text-transform: uppercase; }
.fact-list dd { margin: 0; font-family: var(--serif); }

.ink-section { width: 100%; max-width: none; color: var(--paper); background: var(--ink); }
.interface-heading { width: min(100%, var(--max-width)); margin-inline: auto; padding-inline: var(--page-pad); }
.interface-heading h2 em, .support-heading h2 em { color: rgb(249 248 246 / 55%); }
.interface-heading > p:last-child { max-width: 31rem; margin-top: 2rem; color: rgb(249 248 246 / 68%); line-height: 1.8; }
.screen-gallery { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: clamp(1.5rem, 4vw, 4rem); width: min(100%, var(--max-width)); margin: 6rem auto 0; padding-inline: var(--page-pad); }
.screen-card { margin: 0; }
.screen-card-offset { padding-top: 7rem; }
.screen-card .screen-frame { color: rgb(249 248 246 / 25%); }
.screen-card figcaption { color: rgb(249 248 246 / 55%); }

.features .section-heading { position: sticky; top: 8rem; align-self: start; }
.feature-list { grid-column: 7 / -1; margin: 0; padding: 0; list-style: none; border-top: 1px solid var(--ink-16); }
.feature-row { display: grid; grid-template-columns: 3rem 1fr auto; gap: 1rem; align-items: start; min-height: 13rem; padding: 2rem 0; border-bottom: 1px solid var(--ink-16); transition: background 500ms ease, border-color 500ms ease; }
.feature-row:hover { border-color: var(--ink-40); background: rgb(28 28 28 / 2%); }
.feature-number { padding-top: 0.35rem; color: var(--ink-muted); font-size: 0.7rem; letter-spacing: 0.14em; }
.feature-row h3 { margin: 0; font-size: clamp(2rem, 3vw, 3.2rem); letter-spacing: -0.04em; transition: font-style 500ms ease; }
.feature-row:hover h3 { font-style: italic; }
.feature-row p { max-width: 30rem; margin: 1.25rem 0 0; color: var(--ink-muted); line-height: 1.8; }
.feature-mark { font-family: var(--serif); font-size: 1.25rem; }

.guide-intro { grid-column: 1 / span 5; }
.guide-intro > p:last-child { max-width: 28rem; margin-top: 2rem; color: var(--ink-muted); line-height: 1.8; }
.steps { grid-column: 7 / -1; margin: 0; padding: 0; list-style: none; }
.step { display: grid; grid-template-columns: 4rem 1fr; gap: 1rem; min-height: 11rem; padding: 2rem 0; border-top: 1px solid var(--ink-16); }
.step:last-child { border-bottom: 1px solid var(--ink-16); }
.step > span { color: var(--ink-muted); font-size: 0.7rem; letter-spacing: 0.16em; }
.step h3 { margin: 0; font-size: clamp(1.7rem, 2.8vw, 2.7rem); }
.step p { max-width: 30rem; color: var(--ink-muted); line-height: 1.8; }

.flash-heading { grid-column: 1 / -1; }
.flash-workbench { grid-column: 1 / span 9; margin-top: 2rem; border: 1px solid var(--ink-16); }
.flash-status-line { display: flex; justify-content: space-between; gap: 1rem; padding: 1rem 1.25rem; border-bottom: 1px solid var(--ink-16); color: var(--ink-muted); font-size: 0.7rem; letter-spacing: 0.12em; text-transform: uppercase; }
.flash-status-line > div { display: flex; align-items: center; gap: 0.75rem; }
.status-dot { width: 0.5rem; height: 0.5rem; border: 1px solid currentColor; background: transparent; }
.flash-status-line[data-ready] .status-dot { background: currentColor; }
.flash-grid { display: grid; grid-template-columns: 1.1fr 0.9fr; }
.flash-copy, .checklist { padding: clamp(2rem, 5vw, 4.5rem); }
.flash-copy { border-right: 1px solid var(--ink-16); }
.flash-kicker { margin: 0 0 2rem; color: var(--ink-muted); font-size: 0.7rem; letter-spacing: 0.16em; text-transform: uppercase; }
.flash-copy h3 { margin: 0; font-size: clamp(2.5rem, 4vw, 4.5rem); letter-spacing: -0.04em; }
.flash-copy p:not(.flash-kicker) { max-width: 32rem; margin: 2rem 0; color: var(--ink-muted); line-height: 1.8; }
.checklist { margin: 0; border: 0; }
.checklist label { display: grid; grid-template-columns: 1.25rem 1fr; gap: 1rem; padding: 1.2rem 0; border-bottom: 1px solid var(--ink-10); color: var(--ink-muted); font-size: 0.9rem; line-height: 1.6; }
.checklist input { width: 1.1rem; height: 1.1rem; margin: 0.15rem 0 0; border-radius: 0; accent-color: var(--ink); }
.flash-progress { display: grid; grid-template-columns: repeat(5, 1fr); margin: 0; padding: 0; border-top: 1px solid var(--ink-16); list-style: none; }
.flash-progress li { min-height: 5.5rem; padding: 1rem; border-right: 1px solid var(--ink-10); color: var(--ink-muted); font-size: 0.7rem; letter-spacing: 0.08em; }
.flash-progress li:last-child { border-right: 0; }
.flash-progress span { display: block; margin-bottom: 1.25rem; }
.safety-note { grid-column: 10 / -1; align-self: end; margin-top: 2rem; padding: 1.5rem 0; border-top: 1px solid var(--ink); border-bottom: 1px solid var(--ink-16); }
.safety-note h3 { margin: 1.5rem 0; font-size: 1.55rem; line-height: 1.35; }
.safety-note > p:last-child { color: var(--ink-muted); font-size: 0.86rem; line-height: 1.8; }

.support { padding-inline: max(var(--page-pad), calc((100% - var(--max-width)) / 2 + var(--page-pad))); }
.support-heading { display: grid; grid-template-columns: repeat(12, 1fr); }
.support-heading .label { grid-column: 1 / -1; }
.support-heading h2 { grid-column: 1 / span 8; }
.faq-list { margin-top: 6rem; border-top: 1px solid rgb(249 248 246 / 18%); }
.faq-list details { border-bottom: 1px solid rgb(249 248 246 / 18%); }
.faq-list summary { display: flex; min-height: 5.5rem; align-items: center; justify-content: space-between; gap: 2rem; font-family: var(--serif); font-size: clamp(1.2rem, 2vw, 1.7rem); cursor: pointer; list-style: none; }
.faq-list summary::-webkit-details-marker { display: none; }
.faq-list summary span:last-child { color: rgb(249 248 246 / 55%); transition: transform 300ms ease; }
.faq-list details[open] summary span:last-child { transform: rotate(45deg); }
.faq-list details p { max-width: 44rem; margin: 0 0 2rem; color: rgb(249 248 246 / 65%); line-height: 1.9; }

.closing {
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  min-height: 85svh;
  border-top: 1px solid var(--ink-16);
  border-bottom: 1px solid var(--ink-16);
  text-align: center;
}
.closing h2 { margin-inline: auto; }
.closing h2 em { display: inline-block; }
.closing .button { margin-top: 4rem; }

.site-footer { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 2rem; padding: 4rem var(--page-pad); border-top: 1px solid var(--ink-16); }
.site-footer p { margin: 0; color: var(--ink-muted); font-size: 0.7rem; letter-spacing: 0.09em; line-height: 1.8; text-transform: uppercase; }

.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0; }

.js .reveal { opacity: 0; transform: translateY(1rem); transition: opacity 650ms ease, transform 650ms ease; }
.js .reveal[data-visible] { opacity: 1; transform: translateY(0); }

@media (max-width: 1100px) {
  .hero-copy { grid-column: 1 / span 8; }
  .hero-visual { grid-column: 9 / -1; }
  .screen-frame-hero { width: 18rem; }
  .flash-workbench { grid-column: 1 / -1; }
  .safety-note { grid-column: 1 / -1; max-width: 38rem; }
}

@media (max-width: 879px) {
  .site-header { min-height: 4.5rem; }
  .menu-toggle { display: flex; align-items: center; justify-content: flex-end; gap: 0.75rem; padding: 0; }
  .menu-mark, .menu-mark::after { display: block; width: 1rem; height: 1px; background: currentColor; content: ""; transition: transform 300ms ease; }
  .menu-mark::after { transform: translateY(0.3rem); }
  .menu-toggle[aria-expanded="true"] .menu-mark { transform: rotate(45deg); }
  .menu-toggle[aria-expanded="true"] .menu-mark::after { transform: rotate(-90deg); }
  .site-nav { position: absolute; top: 100%; right: 0; left: 0; display: none; align-items: stretch; padding: 1rem var(--page-pad) 2rem; border-bottom: 1px solid var(--ink-16); background: var(--paper); }
  .site-nav[data-open] { display: grid; }
  .site-nav a { display: flex; min-height: 3rem; align-items: center; border-bottom: 1px solid var(--ink-10); }
  .site-nav .nav-cta { margin-top: 0.5rem; padding-inline: 1rem; border: 0; }

  .hero { grid-template-columns: 1fr; padding-top: 8rem; }
  .hero-copy, .hero-visual { grid-column: 1; }
  .hero-visual { margin-top: 6rem; }
  .screen-frame-hero { width: min(80vw, 22rem); margin-inline: auto; }
  .hero-index { display: none; }

  .philosophy, .features, .guide, .flash-section { grid-template-columns: 1fr; gap: 4rem; }
  .section-heading, .philosophy-body, .feature-list, .guide-intro, .steps, .flash-heading, .flash-workbench, .safety-note { grid-column: 1; }
  .features .section-heading { position: static; }
  .screen-gallery { grid-template-columns: 1fr; gap: 4.5rem; }
  .screen-card { width: min(72vw, 22rem); }
  .screen-card:nth-child(odd) { justify-self: start; }
  .screen-card:nth-child(even) { justify-self: end; }
  .screen-card-offset { padding-top: 0; }
  .support-heading h2 { grid-column: 1 / -1; }
  .site-footer { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 620px) {
  :root { --section-y: 7rem; }
  .hero h1 { font-size: clamp(3.75rem, 19vw, 6rem); }
  .hero h1 em { font-size: 0.54em; }
  .hero-actions { align-items: flex-start; flex-direction: column; gap: 1rem; }
  .button { width: 100%; }
  .section-heading h2, .guide h2, .flash-heading h2, .interface-heading h2, .support-heading h2, .closing h2 { font-size: clamp(3rem, 14vw, 5rem); }
  .interface-heading h2 { font-size: clamp(2.65rem, 13.5vw, 5rem); }
  .flash-heading h2 { font-size: clamp(2.25rem, 11vw, 4rem); }
  .screen-gallery { grid-template-columns: 1fr; margin-top: 4rem; }
  .screen-card { width: min(78vw, 18rem); margin-inline: auto; justify-self: center; }
  .screen-card-offset { padding-top: 0; }
  .feature-row { grid-template-columns: 2.5rem 1fr; }
  .feature-mark { display: none; }
  .flash-status-line { align-items: flex-start; flex-direction: column; }
  .flash-grid { grid-template-columns: 1fr; }
  .flash-copy { border-right: 0; border-bottom: 1px solid var(--ink-16); }
  .flash-progress { grid-template-columns: 1fr; }
  .flash-progress li { display: grid; grid-template-columns: 3rem 1fr; align-items: center; min-height: auto; border-right: 0; border-bottom: 1px solid var(--ink-10); }
  .flash-progress span { margin: 0; }
  .site-footer { grid-template-columns: 1fr; gap: 2.5rem; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { scroll-behavior: auto !important; transition-duration: 0.01ms !important; animation-duration: 0.01ms !important; animation-iteration-count: 1 !important; }
  .js .reveal { opacity: 1; transform: none; }
}