:root {
  --bg: #ffffff;
  --bg-panel: #f4f7fd;
  --bg-panel-2: #e9eff9;
  --border: #dbe3f0;
  --accent: #1747c9;
  --accent-dark: #0f2f8f;
  --text: #0d1a33;
  --text-muted: #56637b;
  --success: #15804c;
  --warn: #b4741a;
  --error: #c2362f;
  --on-accent: #ffffff;
  --transparent: transparent;
  --accent-soft: rgba(23, 71, 201, .14);
  --accent-faint: rgba(23, 71, 201, .06);
  --success-soft: rgba(21, 128, 76, .16);
  --veil: rgba(13, 26, 51, .32);
  --line-opacity: .12;

  --font-display: "Inter", "Noto Sans SC", "PingFang SC", "Hiragino Sans", "Apple SD Gothic Neo", "Microsoft YaHei", system-ui, sans-serif;
  --font-body: "Inter", "Noto Sans SC", "PingFang SC", "Hiragino Sans", "Apple SD Gothic Neo", "Microsoft YaHei", system-ui, sans-serif;
  --font-mono: "JetBrains Mono", ui-monospace, "SF Mono", Menlo, Consolas, monospace;
  --size-xs: 12px;
  --size-label: 12.5px;
  --size-sm: 14px;
  --size-nav: 14.5px;
  --size-brand: 15px;
  --size-button: 15.5px;
  --size-body: 16px;
  --size-lede: 16.5px;
  --size-intro: 20px;
  --size-h1: clamp(34px, calc(1rem + 2.25vw), 48px);
  --size-h1-mobile: clamp(24px, 4.8vw, 30px);
  --size-h2: 30px;
  --size-h2-mobile: 22px;
  --size-h3: 22px;
  --size-code: 13.5px;
  --size-code-sm: 12px;
  --size-tiny: 11.5px;
  --weight-normal: 400;
  --weight-medium: 500;
  --weight-semibold: 600;
  --weight-strong: 700;
  --weight-display: 800;
  --track-tight: -.025em;
  --track-cjk: -.02em;
  --track-brand: -.01em;
  --track-button: -.005em;
  --track-label: .04em;
  --track-index: .06em;

  --r-panel: 28px;
  --r-card: 24px;
  --r-md: 16px;
  --r-sm: 10px;
  --r-shot: 10px;
  --r-mark: 8px;
  --r-underline: 3px;
  --r-pill: 999px;
  --r-circle: 50%;
  --shadow-card: 0 1px 2px rgba(15, 47, 143, .06), 0 22px 48px -18px rgba(15, 47, 143, .20);
  --shadow-float: 0 2px 6px rgba(15, 47, 143, .08), 0 30px 60px -18px rgba(15, 47, 143, .30);
  --shadow-btn: 0 1px 2px rgba(15, 47, 143, .22), 0 10px 22px -10px rgba(23, 71, 201, .60);
  --shadow-mark: inset 0 0 0 3px var(--bg);

  --gutter: 32px;
  --width-reading: 800px;
  --width-content: 1120px;
  --width-header: 1280px;
  --header-height: 68px;
  --section-space: 96px;
  --ease-out: cubic-bezier(.2, .7, .2, 1);
  --time-ui: .15s;
  --time-reveal: .6s;
}

*, *::before, *::after { box-sizing: border-box; }
html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 24px;
}
html.nav-open { overflow: hidden; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  font-size: var(--size-body);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
body, button, input, select, textarea { font-family: var(--font-body); }
button, input, select, textarea { font-size: inherit; }
button { cursor: pointer; }
button, input, select, textarea { color: var(--text); }
button { background: var(--bg); }
button:disabled { cursor: not-allowed; }
img, svg { vertical-align: middle; }
img { max-width: 100%; }
svg { flex-shrink: 0; }
a { color: inherit; text-decoration: none; }
a:hover { color: var(--accent); }
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: var(--r-sm);
}
[hidden] { display: none !important; }
p, figure, blockquote { margin: 0; }
ul, ol { padding-left: 1.5em; }
h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: var(--weight-display);
  letter-spacing: var(--track-tight);
  line-height: 1.25;
  text-wrap: balance;
  overflow-wrap: break-word;
}
:lang(zh-CN) h1, :lang(zh-CN) h2, :lang(zh-CN) h3,
:lang(zh-TW) h1, :lang(zh-TW) h2, :lang(zh-TW) h3,
:lang(ja) h1, :lang(ja) h2, :lang(ja) h3,
:lang(ko) h1, :lang(ko) h2, :lang(ko) h3 {
  letter-spacing: var(--track-cjk);
}
h1 { font-size: var(--size-h1); line-height: 1.14; }
h2 { font-size: var(--size-h2); }
h3 { font-size: var(--size-h3); }
code, pre, kbd, samp { font-family: var(--font-mono); }
code { overflow-wrap: anywhere; }
pre {
  max-width: 100%;
  min-width: 0;
  overflow-x: auto;
  padding: 20px;
  background: var(--bg-panel);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: var(--r-md);
  font-size: var(--size-code);
  line-height: 1.8;
  overscroll-behavior-inline: contain;
}
pre code { white-space: pre; overflow-wrap: normal; word-break: normal; }
hr { border: 0; border-top: 1px solid var(--border); margin: 32px 0; }
section[id], h2[id], h3[id], [role="tabpanel"] { scroll-margin-top: 24px; }
.wrap {
  width: 100%;
  max-width: calc(var(--width-content) + var(--gutter) * 2);
  margin-inline: auto;
  padding-inline: var(--gutter);
}
.reading { max-width: calc(var(--width-reading) + var(--gutter) * 2); }
.section { padding-top: var(--section-space); padding-bottom: var(--section-space); }
.section-heading { max-width: 760px; margin: 0 0 32px; }
.section-heading h2 { margin: 10px 0 16px; }
.section-heading p, .muted { color: var(--text-muted); }
.stack > * + * { margin-top: 20px; }
.grid-two { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 24px; }
.grid-three { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 24px; }
.grid-two > *, .grid-three > *, .wrap > *, .topbar > * { min-width: 0; }
.nowrap { white-space: nowrap; }
.sr-only {
  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;
  top: 8px;
  left: var(--gutter);
  z-index: 100;
  transform: translateY(-180%);
  padding: 10px 18px;
  background: var(--accent);
  color: var(--on-accent);
  border-radius: var(--r-pill);
}
.skip-link:focus { transform: none; color: var(--on-accent); }
.prose { min-width: 0; overflow-wrap: break-word; }
.prose > * + * { margin-top: 20px; }
.prose h2 { margin-top: 56px; }
.prose h3 { margin-top: 32px; }
.prose p, .prose li { line-height: 1.9; }
.prose a { color: var(--accent); text-decoration: underline; text-underline-offset: .2em; }
.prose :not(pre) > code {
  background: var(--bg-panel);
  color: var(--accent-dark);
  border-radius: var(--r-underline);
  padding: .08em .25em;
}
.prose li + li { margin-top: 8px; }
.card {
  padding: 28px;
  background: var(--bg);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: var(--r-card);
  box-shadow: var(--shadow-card);
  min-width: 0;
}
.card h3 { margin: 0 0 16px; }
.card p { color: var(--text-muted); }
.panel {
  background: var(--bg-panel);
  color: var(--text);
  border-radius: var(--r-panel);
}
.section-panel { margin-inline: 24px; }
.decorated, .screen, [data-hero-visual] { overflow-x: clip; }
.tilt { transform: rotate(.45deg); }

.btn {
  display: inline-flex;
  justify-content: center;
  align-items: center;
  gap: 9px;
  min-height: 50px;
  max-width: 100%;
  padding: 12px 26px;
  border: 1px solid var(--transparent);
  border-radius: var(--r-pill);
  font-family: var(--font-display);
  font-weight: var(--weight-strong);
  font-size: var(--size-button);
  letter-spacing: var(--track-button);
  line-height: 1.5;
  text-align: center;
  transition: background-color var(--time-ui), border-color var(--time-ui), color var(--time-ui);
}
.btn svg { width: 18px; height: 18px; }
.btn-primary {
  background: var(--accent);
  color: var(--on-accent);
  box-shadow: var(--shadow-btn);
}
.btn-primary:hover, .btn-primary.is-hover { background: var(--accent-dark); color: var(--on-accent); }
.btn-primary:active { background: var(--accent-dark); color: var(--on-accent); }
.btn-ghost { background: var(--bg); color: var(--text); border: 1.5px solid var(--accent-dark); }
.btn-ghost:hover, .btn-ghost.is-hover { color: var(--accent); border-color: var(--accent); }
.btn-ghost svg { width: 16px; height: 16px; }
.btn:disabled, .btn[aria-disabled="true"] {
  background: var(--bg-panel-2);
  color: var(--text-muted);
  border-color: var(--border);
  box-shadow: none;
}
.btn.is-focus { outline: 2px solid var(--accent); outline-offset: 3px; }
.button-row { display: flex; flex-wrap: wrap; align-items: center; gap: 14px; }

/* Independent wide header; never reuse the reading width. */
.site-header { position: relative; z-index: 50; background: var(--bg); color: var(--text); }
.topbar {
  position: relative;
  z-index: 2;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  width: 100%;
  max-width: min(100%, calc(var(--width-header) + var(--gutter) * 2));
  min-height: var(--header-height);
  margin-inline: auto;
  padding-inline: var(--gutter);
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 11px;
  justify-self: start;
  flex-shrink: 0;
  font-family: var(--font-display);
  font-weight: var(--weight-strong);
  font-size: var(--size-brand);
  letter-spacing: var(--track-brand);
  color: var(--text);
}
.brand:hover { color: var(--text); }
.brand img, .brand-mark {
  width: 32px;
  height: 32px;
  flex-shrink: 0;
  border-radius: var(--r-mark);
}
.brand-mark {
  display: inline-block;
  background: var(--bg-panel-2);
  color: var(--text);
  border: 1px solid var(--border);
  box-shadow: var(--shadow-mark);
}
.desktop-nav { min-width: 0; }
.dotnav {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0;
  list-style: none;
  margin: 0;
  padding: 0;
  font-size: var(--size-nav);
  color: var(--text-muted);
}
.dotnav li { display: flex; align-items: center; flex-shrink: 0; }
.dotnav li + li::before {
  content: "·";
  padding-inline: 13px;
  color: var(--border);
  font-weight: var(--weight-strong);
}
.dotnav a { display: block; padding-top: 6px; padding-bottom: 6px; }
.dotnav a[aria-current="page"] { color: var(--text); font-weight: var(--weight-semibold); }
.header-tools {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 8px;
  justify-self: end;
  flex-shrink: 0;
}
.lang {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  min-height: 44px;
  padding: 6px 2px;
  border: 0;
  background: var(--transparent);
  color: var(--text-muted);
  font-size: var(--size-sm);
  white-space: nowrap;
}
.lang svg { width: 16px; height: 16px; }
.lang-caret { font-size: var(--size-tiny); }
.lang-short { display: none; }
.language-picker { position: relative; }
.language-menu {
  position: absolute;
  z-index: 5;
  top: calc(100% + 6px);
  right: 0;
  width: 192px;
  padding: 8px;
  margin: 0;
  list-style: none;
  background: var(--bg);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: var(--r-md);
  box-shadow: var(--shadow-card);
}
.language-menu a {
  display: flex;
  align-items: center;
  width: 100%;
  min-height: 44px;
  padding: 10px 12px;
  border-radius: var(--r-sm);
}
.language-menu a:hover, .language-menu a[aria-current="true"] {
  background: var(--bg-panel);
  color: var(--accent-dark);
}
.menu-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  min-width: 44px;
  min-height: 44px;
  padding: 10px;
  border: 1px solid var(--border);
  border-radius: var(--r-sm);
  background: var(--bg);
  color: var(--accent-dark);
}
.menu-toggle svg { width: 22px; height: 22px; }
.mobile-drawer {
  position: absolute;
  z-index: 4;
  top: 100%;
  left: var(--gutter);
  right: var(--gutter);
  max-height: calc(100dvh - var(--header-height) - 16px);
  overflow-y: auto;
  overscroll-behavior: contain;
  padding: 16px;
  background: var(--bg);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: var(--r-md);
  box-shadow: var(--shadow-float);
}
.mobile-drawer ul { margin: 0; padding: 0; list-style: none; }
.mobile-drawer a {
  display: flex;
  align-items: center;
  width: 100%;
  min-height: 48px;
  padding: 12px 16px;
  border-radius: var(--r-sm);
}
.mobile-drawer a:hover, .mobile-drawer a[aria-current] {
  background: var(--bg-panel);
  color: var(--accent-dark);
}
.drawer-label { margin: 16px 16px 6px; font-size: var(--size-xs); color: var(--text-muted); }
.drawer-languages { border-top: 1px solid var(--border); padding-top: 8px; }
.menu-veil {
  position: fixed;
  z-index: 1;
  inset: var(--header-height) 0 0;
  border: 0;
  background: var(--veil);
  color: var(--text);
}

/* Approved first-screen composition. */
.screen { position: relative; background: var(--bg); color: var(--text); }
.bg-lines { position: absolute; inset: 0; width: 100%; height: 100%; z-index: 0; pointer-events: none; }
.bg-lines line {
  stroke: var(--accent);
  stroke-opacity: var(--line-opacity);
  stroke-width: 1;
  vector-effect: non-scaling-stroke;
}
.hero { position: relative; z-index: 1; padding: 34px 40px 26px; text-align: center; }
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  min-height: 28px;
  max-width: 100%;
  padding: 3px 13px;
  border: 1px solid var(--border);
  border-radius: var(--r-pill);
  background: var(--bg-panel);
  color: var(--accent-dark);
  font-size: var(--size-label);
  font-weight: var(--weight-semibold);
  letter-spacing: var(--track-label);
}
.eyebrow-dot { width: 6px; height: 6px; flex-shrink: 0; border-radius: var(--r-circle); background: var(--accent); }
.h1 { margin: 18px auto 0; font-size: var(--size-h1); line-height: 1.14; }
.h1-line { display: block; animation: title-rise .62s var(--ease-out) both; }
.h1-line--a { color: var(--accent); }
.h1-line--b { color: var(--accent-dark); animation-delay: .16s; }
.mark { position: relative; display: inline-block; z-index: 0; }
.mark::after {
  content: "";
  position: absolute;
  left: -.06em;
  right: -.06em;
  bottom: .06em;
  height: .26em;
  z-index: -1;
  border-radius: var(--r-underline);
  background: var(--accent-soft);
  transform-origin: 0 50%;
  animation: title-sweep .56s var(--ease-out) .58s both;
}
@keyframes title-rise {
  from { opacity: 0; transform: translateY(18px); }
  to { opacity: 1; transform: none; }
}
@keyframes title-sweep {
  from { transform: scaleX(0); }
  to { transform: scaleX(1); }
}
.cta { display: flex; justify-content: center; gap: 14px; margin-top: 24px; }
.lede { max-width: 760px; margin: 20px auto 0; font-size: var(--size-lede); line-height: 1.65; color: var(--text-muted); }
.lede strong { color: var(--text); font-weight: var(--weight-semibold); }
.devices {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
  gap: 22px;
  padding: 0;
  margin: 18px 0 0;
  list-style: none;
  font-size: var(--size-sm);
  font-weight: var(--weight-medium);
  color: var(--text);
}
.devices li, .devices a { display: inline-flex; align-items: center; gap: 7px; }
.devices .dev-ico { width: 20px; height: 20px; color: var(--accent); }
.devices-sep { width: 1px; height: 18px; flex-shrink: 0; background: var(--border); }
.pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  min-height: 30px;
  max-width: 100%;
  padding: 4px 12px;
  border: 1px solid var(--border);
  border-radius: var(--r-pill);
  background: var(--bg-panel);
  color: var(--accent-dark);
  font-size: var(--size-label);
  font-weight: var(--weight-semibold);
  overflow-wrap: anywhere;
}
.pill svg { width: 13px; height: 13px; }

.site-footer {
  margin-top: 64px;
  padding-top: 64px;
  padding-bottom: 32px;
  border-top: 1px solid var(--border);
  background: var(--bg-panel);
  color: var(--text);
}
.footer-grid { display: grid; grid-template-columns: 1.3fr .8fr 1.2fr .7fr; gap: 40px; }
.footer-grid > * { min-width: 0; }
.footer-brand p { max-width: 320px; margin-top: 20px; color: var(--text-muted); font-size: var(--size-sm); }
.footer-title { margin: 0 0 16px; font-size: var(--size-sm); font-weight: var(--weight-strong); }
.footer-links { list-style: none; padding: 0; margin: 0; font-size: var(--size-sm); }
.footer-links li + li { margin-top: 8px; }
.footer-links a { display: inline-block; padding-top: 3px; padding-bottom: 3px; overflow-wrap: anywhere; }
.footer-bottom {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  gap: 16px 24px;
  margin-top: 40px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: var(--size-xs);
}
.footer-legal { display: flex; flex-wrap: wrap; gap: 20px; }
.footer-trademark { flex-basis: 100%; }
.reveal { opacity: 1; transition: opacity var(--time-reveal) var(--ease-out), transform var(--time-reveal) var(--ease-out); }
.reveal-ready .reveal:not(.shown) { opacity: 0; transform: translateY(18px); }
.reveal.shown { opacity: 1; transform: none; }

@media (max-width: 1199px) {
  .site-header .topbar { display: flex; justify-content: space-between; gap: 16px; }
  .site-header .desktop-nav { display: none; }
  .site-header .brand { flex-shrink: 1; min-width: 0; }
  .site-header .brand span { min-width: 0; overflow-wrap: anywhere; }
  .site-header .header-tools { margin-left: auto; }
  .site-header .menu-toggle { display: inline-flex; }
}
@media (max-width: 1199px) {
  .preview-topbar { grid-template-columns: 1fr auto; row-gap: 4px; padding-top: 14px; padding-bottom: 14px; }
  .preview-topbar .desktop-nav { grid-column: 1 / -1; grid-row: 2; }
  .preview-topbar .dotnav { flex-wrap: wrap; }
  .footer-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 768px) {
  :root { --gutter: 20px; --section-space: 64px; }
  h1, .h1 { font-size: var(--size-h1-mobile); }
  h2 { font-size: var(--size-h2-mobile); }
  .hero { padding: 26px 20px 20px; }
  .dotnav { font-size: var(--size-code); }
  .dotnav li + li::before { padding-inline: 8px; }
  .brand { font-size: var(--size-sm); }
  .hero .cta { flex-direction: column; align-items: stretch; max-width: 320px; margin-inline: auto; }
  .lede { font-size: var(--size-brand); }
  .devices { gap: 12px 16px; }
  .devices-sep { display: none !important; }
  .grid-three { grid-template-columns: 1fr; }
  .section-panel { margin-inline: 12px; }
}
@media (max-width: 640px) {
  :root { --gutter: 16px; }
  .grid-two, .footer-grid { grid-template-columns: minmax(0, 1fr); }
  .card { padding: 24px; }
  .tilt, [data-tilt] { transform: none !important; }
  .site-header .brand span, .preview-topbar .brand > span:last-child { font-size: var(--size-xs); }
  .site-header .brand { gap: 7px; }
  .site-header .topbar { gap: 8px; }
  .lang-full { display: none; }
  .lang-short { display: inline; }
  .header-tools { margin-left: auto; }
  .site-header .lang { padding-inline: 4px; }
  .footer-grid { gap: 28px; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .h1-line, .mark::after { animation: none; opacity: 1; transform: none; }
  .reveal, .reveal-ready .reveal:not(.shown) { opacity: 1; transform: none; transition: none; }
  .btn { transition: none; }
}