:root {
  --bg: #F4F7FC;
  --bg-panel: #FFFFFF;
  --bg-panel-2: #ECF1F8;
  --bg-inset: #F6F8FC;
  --border: #D9E1EC;
  --border-soft: #E6ECF4;
  --border-strong: #C3CFDE;
  --accent: #1D6FD8;
  --accent-dark: #1556AB;
  --on-accent: #FFFFFF;
  --text: #1F2A37;
  --text-muted: #5B6778;
  --text-faint: #8C97A7;
  --success: #2E8B57;
  --success-ink: #256F46;
  --warn: #C98A04;
  --warn-ink: #805803;
  --error: #C8412F;
  --mark: #FFE27A;
  --dot: #CBD4E0;
  --clear: transparent;
  --veil: rgba(31, 42, 55, .22);
  --font-display: "Inter", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-body: "Inter", "Noto Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
  --font-mono: "JetBrains Mono", ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
  --r-sm: 4px;
  --r: 6px;
  --r-lg: 8px;
  --r-pill: 999px;
  --r-round: 50%;
  --shadow-soft: 0 1px 2px rgba(31,42,55,.04), 0 4px 14px -6px rgba(31,42,55,.08);
  --shadow-card: 0 1px 2px rgba(31,42,55,.035), 0 10px 24px -14px rgba(31,42,55,.14);
  --shadow-window: 0 2px 8px rgba(31,42,55,.05), 0 44px 96px -34px rgba(21,86,171,.30);
  --shadow-btn: 0 1px 2px rgba(21,86,171,.20), 0 10px 22px -10px rgba(29,111,216,.55);
  --shadow-segment: 0 0 0 1px var(--border), 0 1px 2px rgba(31,42,55,.06);
  --nav-h: 72px;
  --gutter: 40px;
  --wrap-max: 1376px;
  --reading-max: 880px;
  --text-size: 16px;
  --h1-size: clamp(34px, 3.4vw, 48px);
  --h2-size: clamp(24px, 2.5vw, 32px);
  --h3-size: 22px;
  --ease: 160ms ease;
  --reveal-time: 480ms;
}

*, *::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(--text-size);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
[hidden] { display: none !important; }
img, svg { max-width: 100%; vertical-align: middle; }
img { height: auto; }
button, input, select, textarea { font: inherit; }
button { cursor: pointer; }
button, a, input, summary { -webkit-tap-highlight-color: var(--clear); }
a { color: inherit; text-underline-offset: 4px; }
a:hover { text-decoration-thickness: 2px; }
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: var(--r-sm);
}
h1, h2, h3 {
  font-family: var(--font-display);
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: -.02em;
  text-wrap: balance;
  overflow-wrap: break-word;
}
h1 { font-size: var(--h1-size); line-height: 1.13; }
h2 { font-size: var(--h2-size); }
h3 { font-size: var(--h3-size); }
p { margin-top: 0; }
code, pre, kbd { font-family: var(--font-mono); }
code { overflow-wrap: anywhere; font-size: .9em; }
pre {
  max-width: 100%;
  min-width: 0;
  overflow-x: auto;
  padding: 20px;
  border: 1px solid var(--border);
  border-radius: var(--r);
  background: var(--bg-panel-2);
  color: var(--text);
  line-height: 1.8;
  tab-size: 2;
}
pre code { white-space: pre; overflow-wrap: normal; font-size: 13px; }
hr { border: 0; border-top: 1px solid var(--border); margin-block: 32px; }
.wrap {
  width: 100%;
  max-width: var(--wrap-max);
  margin-inline: auto;
  padding-inline: var(--gutter);
}
.reading { max-width: calc(var(--reading-max) + var(--gutter) * 2); }
.section { padding-top: 80px; padding-bottom: 80px; }
.section-head { margin-bottom: 32px; }
.section-head h2 { margin: 0 0 12px; }
.kicker { margin: 0 0 8px; font-size: 13px; font-weight: 700; color: var(--accent); }
.muted, .meta { color: var(--text-muted); }
.meta { font-size: 13px; }
.keep { white-space: nowrap; }
.text-link, .prose a:not([class*="btn"]):not([class*="button"]) {
  color: var(--accent);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 4px;
}
.text-link:hover, .prose a:not([class*="btn"]):not([class*="button"]):hover { color: var(--accent-dark); }
.hl {
  color: inherit;
  background: linear-gradient(to bottom, var(--clear) 54%, var(--mark) 54%, var(--mark) 94%, var(--clear) 94%);
  padding: 0 .12em;
  -webkit-box-decoration-break: clone;
  box-decoration-break: clone;
}
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  min-height: 50px;
  max-width: 100%;
  padding: 10px 22px;
  border: 1px solid var(--clear);
  border-radius: var(--r);
  font-family: var(--font-body);
  font-size: 16px;
  font-weight: 700;
  text-align: center;
  text-decoration: none;
  line-height: 1.5;
  transition: background-color var(--ease), border-color var(--ease);
}
.btn svg { width: 18px; height: 18px; flex-shrink: 0; }
.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); box-shadow: none; }
.btn-ghost {
  background: var(--bg-panel);
  color: var(--text);
  border-color: var(--border);
  box-shadow: var(--shadow-soft);
}
.btn-ghost:hover, .btn-ghost.is-hover { border-color: var(--border-strong); }
.btn:disabled, .btn[aria-disabled="true"] {
  background: var(--bg-panel-2);
  color: var(--text-muted);
  border-color: var(--border);
  box-shadow: none;
  cursor: not-allowed;
}
.btn-small { min-height: 44px; padding: 8px 16px; font-size: 14px; }
.cta-row { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 30px; }
.card, .panel {
  min-width: 0;
  padding: 24px;
  background: var(--bg-panel);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: var(--r);
  box-shadow: var(--shadow-card);
}
.card h3 { margin-top: 0; }
.card > :last-child, .panel > :last-child { margin-bottom: 0; }
.card-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 24px; }
.card-grid > *, .hero-grid > *, .footer-grid > *, .letter-row > * { min-width: 0; }
.prose { min-width: 0; line-height: 1.9; overflow-wrap: break-word; }
.prose h2 { margin-top: 56px; margin-bottom: 20px; }
.prose h3 { margin-top: 32px; margin-bottom: 14px; }
.prose p, .prose ul, .prose ol { margin-bottom: 24px; }
.prose li + li { margin-top: 8px; }
.prose :is(h2, h3, section)[id] { scroll-margin-top: 24px; }

.topbar, #site-header { position: relative; z-index: 50; min-height: var(--nav-h); }
.header-wrap {
  width: 100%;
  max-width: min(100%, calc(1280px + var(--gutter) * 2));
  margin-inline: auto;
  padding-inline: var(--gutter);
  min-height: var(--nav-h);
  display: flex;
  align-items: center;
  gap: 28px;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  flex-shrink: 0;
  color: var(--text);
  text-decoration: none;
  font-family: var(--font-display);
  font-size: 21px;
  font-weight: 800;
  letter-spacing: -.01em;
}
.brand-mark { width: 38px; height: 38px; flex-shrink: 0; }
.nav { margin-left: auto; min-width: 0; }
.nav ul {
  display: flex;
  align-items: center;
  gap: 30px;
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav a {
  display: inline-flex;
  align-items: center;
  min-height: 44px;
  color: var(--text-muted);
  text-decoration: none;
  font-size: 15px;
  font-weight: 500;
  white-space: nowrap;
}
.nav a:hover { color: var(--text); }
.nav a[aria-current="page"], .drawer a[aria-current="page"] { color: var(--text); font-weight: 700; }
.header-tools { display: flex; align-items: center; gap: 10px; flex-shrink: 0; }
.language { position: relative; }
.lang {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 36px;
  padding: 6px 12px;
  font-size: 14px;
  font-weight: 600;
  color: var(--text);
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: var(--r);
  white-space: nowrap;
  cursor: pointer;
}
.lang:hover { border-color: var(--border-strong); }
.lang-short { display: none; }
.language-menu {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  min-width: 180px;
  padding: 6px;
  list-style: none;
  margin: 0;
  background: var(--bg-panel);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: var(--r);
  box-shadow: var(--shadow-card);
  z-index: 55;
}
.language-menu a, .drawer a {
  display: flex;
  align-items: center;
  min-height: 44px;
  width: 100%;
  padding: 10px 14px;
  text-decoration: none;
  color: var(--text-muted);
}
.language-menu a:hover, .drawer a:hover { background: var(--bg-panel-2); color: var(--text); }
.language-menu [aria-current="true"] { font-weight: 700; color: var(--text); }
.menu-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  min-width: 44px;
  min-height: 44px;
  border: 1px solid var(--border);
  border-radius: var(--r);
  background: var(--bg-panel);
  color: var(--text);
}
.menu-toggle svg { width: 22px; height: 22px; flex-shrink: 0; }
.drawer {
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  max-height: calc(100dvh - var(--nav-h));
  overflow-y: auto;
  overscroll-behavior: contain;
  background: var(--bg-panel);
  color: var(--text);
  border-bottom: 1px solid var(--border);
  padding: 12px var(--gutter) 24px;
  z-index: 54;
}
.drawer ul { list-style: none; padding: 0; margin: 0; }
.drawer-languages { border-top: 1px solid var(--border); padding-top: 12px; margin-top: 12px; }
.drawer-title { padding-inline: 14px; font-size: 13px; color: var(--text-muted); }
.nav-veil {
  position: fixed;
  inset: var(--nav-h) 0 0;
  z-index: 40;
  border: 0;
  background: var(--veil);
  color: var(--text);
}
.preview-mobile { display: none; position: relative; }
.preview-mobile summary { list-style: none; }
.preview-mobile nav {
  position: absolute;
  right: 0;
  top: calc(100% + 8px);
  width: min(280px, calc(100vw - var(--gutter) * 2));
  background: var(--bg-panel);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 8px;
  box-shadow: var(--shadow-card);
}
.preview-mobile nav a { display: flex; align-items: center; min-height: 44px; padding: 10px 14px; text-decoration: none; }

.hero {
  min-height: calc(100svh - var(--nav-h) - 36px);
  display: grid;
  align-content: center;
  padding-top: 16px;
  padding-bottom: 24px;
  overflow-x: clip;
}
.hero-grid { display: grid; grid-template-columns: 42fr 58fr; gap: 48px; align-items: stretch; }
.hero-copy { display: flex; flex-direction: column; justify-content: space-between; gap: 40px; padding-block: 2px 6px; min-width: 0; }
.qa-index { list-style: none; margin: 0; padding: 0; display: grid; gap: 9px; font-size: 18px; line-height: 1.55; }
.qa-index a { color: var(--accent); font-weight: 700; text-decoration: underline; text-decoration-thickness: 2px; text-underline-offset: 5px; }
.qa-index a:hover { color: var(--accent-dark); }
.qa-index .sep { color: var(--text-faint); margin-inline: .45em; }
.qa-index .note { color: var(--text); }
.hero-title { margin: 0; font-size: var(--h1-size); font-weight: 800; line-height: 1.13; letter-spacing: -.02em; }
.lede { margin: 18px 0 0; max-width: 33em; font-size: 16.5px; line-height: 1.8; color: var(--text-muted); }
.lede strong { color: var(--text); font-weight: 700; }
.platforms { display: flex; flex-wrap: wrap; gap: 8px; margin: 22px 0 0; padding: 0; list-style: none; }
.pf {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 7px;
  min-height: 32px;
  padding: 5px 13px;
  border: 1px solid var(--border);
  border-radius: var(--r-pill);
  background: var(--bg-panel);
  color: var(--text);
  font-size: 13px;
  font-weight: 600;
  text-decoration: none;
}
.pf svg { width: 14px; height: 14px; flex-shrink: 0; color: var(--text-muted); }
.pf:hover { border-color: var(--accent); color: var(--accent); }
.pf:hover svg { color: var(--accent); }
.peek { padding-bottom: 48px; }
.peek-inner { border-top: 1px solid var(--border); padding-top: 14px; }
.peek h2 { margin: 0; font-size: 30px; }
.peek-desc { margin: 10px 0 0; color: var(--text-muted); max-width: 40em; }

.site-footer {
  margin-top: 64px;
  padding-top: 48px;
  padding-bottom: 96px;
  border-top: 1px solid var(--border);
}
.footer-grid { display: grid; grid-template-columns: 1.3fr .8fr 1.15fr .65fr; gap: 40px; }
.footer-brand p { margin-top: 18px; max-width: 28em; color: var(--text-muted); font-size: 14px; }
.footer-title { margin: 0 0 16px; font-size: 13px; font-weight: 700; color: var(--accent); }
.footer-list { list-style: none; padding: 0; margin: 0; }
.footer-list li + li { margin-top: 10px; }
.footer-list a { color: var(--text-muted); font-size: 14px; text-decoration: none; }
.footer-list a:hover { text-decoration: underline; color: var(--text); }
.footer-bottom { display: flex; flex-wrap: wrap; gap: 16px; justify-content: space-between; margin-top: 40px; padding-top: 20px; border-top: 1px solid var(--border); font-size: 13px; color: var(--text-muted); }
.reveal { opacity: 1; transform: none; }
.reveal-ready .reveal:not(.shown) { opacity: 0; transform: translateY(12px); }
.reveal-ready .reveal { transition: opacity var(--reveal-time) ease, transform var(--reveal-time) ease; }
.reveal-ready .reveal.shown { opacity: 1; transform: none; }

@media (max-width: 1200px) {
  .nav { display: none; }
  .header-tools { margin-left: auto; }
  .menu-toggle { display: inline-flex; }
  .preview-mobile { display: block; }
}
@media (min-width: 1201px) {
  .drawer, .nav-veil { display: none !important; }
}
@media (max-width: 1100px) {
  .hero { min-height: 0; padding-top: 24px; padding-bottom: 56px; }
  .hero-grid { grid-template-columns: minmax(0, 1fr); gap: 48px; }
  .hero-copy { gap: 44px; }
  .footer-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 768px) {
  :root { --gutter: 20px; --h1-size: 28px; --h2-size: 26px; }
  .section { padding-top: 48px; padding-bottom: 48px; }
  h1 .keep, h2 .keep { white-space: normal; }
  .card-grid { grid-template-columns: minmax(0, 1fr); }
  .qa-index { font-size: 16px; }
  .lede { font-size: 15.5px; }
  .peek h2 { font-size: 24px; }
  .header-wrap { gap: 12px; }
}
@media (max-width: 640px) {
  .tilt, [data-tilt] { transform: none !important; }
  .lang-long { display: none; }
  .lang-short { display: inline; }
  .header-tools { margin-left: auto; gap: 8px; }
  .brand { font-size: 18px; gap: 8px; }
  .brand-mark { width: 32px; height: 32px; }
  .lang { padding-inline: 10px; min-height: 44px; }
  .footer-grid { grid-template-columns: minmax(0, 1fr); gap: 28px; }
  .card, .panel { padding: 20px; }
  .platforms { column-gap: 6px; row-gap: 8px; }
  .pf { padding-inline: 10px; }
}
@media (max-width: 360px) {
  :root { --gutter: 16px; }
  .brand { font-size: 16px; gap: 6px; }
  .header-wrap { gap: 8px; }
  .btn { padding-inline: 16px; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation: none !important; transition: none !important; }
  .reveal-ready .reveal:not(.shown) { opacity: 1; transform: none; }
}