:root {
  --c-sky: #C6E1FB;
  --c-sky-top: #B9D9FA;
  --c-sky-bottom: #DCEBFC;
  --c-panel: #FFFFFF;
  --c-panel-2: #EEF5FD;
  --c-border: #D3E1EF;
  --c-accent: #FF4A3D;
  --c-accent-dark: #D3301F;
  --c-accent-soft: #FFE7E3;
  --c-accent-glow: rgba(255, 74, 61, .42);
  --c-ink: #0E1A2B;
  --c-ink-soft: #1D2C42;
  --c-ink-card: #0F2747;
  --c-sky-card: #E3F0FD;
  --c-muted: #4D5E73;
  --c-faint: #8C9CB0;
  --c-success: #17A673;
  --c-success-halo: rgba(23, 166, 115, .18);
  --c-warn: #E39B12;
  --c-error: #C21F3A;
  --c-edge: #DEE6EF;
  --c-edge-deep: #C8D5E3;
  --c-track: #CFD9E5;
  --c-glass: rgba(255, 255, 255, .56);
  --c-glass-line: rgba(255, 255, 255, .88);
  --c-cloud: rgba(255, 255, 255, .74);
  --c-cloud-0: rgba(255, 255, 255, 0);
  --c-on-ink-muted: rgba(255, 255, 255, .72);
  --c-on-ink-soft: rgba(255, 255, 255, .10);
  --c-veil: rgba(14, 26, 43, .32);
  --c-clear: transparent;
  --sh-tint-1: rgba(31, 62, 104, .06);
  --sh-tint-2: rgba(31, 62, 104, .10);
  --sh-tint-3: rgba(31, 62, 104, .15);

  --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;
  --fs-xs: 12px;
  --fs-sm: 14px;
  --fs-body: 16px;
  --fs-lead: 18px;
  --fs-h3: 24px;
  --fs-h2: clamp(24px, 2.5vw, 36px);
  --fs-h1: clamp(34px, 3.4vw, 48px);
  --weight-normal: 400;
  --weight-medium: 500;
  --weight-semibold: 600;
  --weight-bold: 700;
  --weight-heavy: 800;
  --weight-display: 900;
  --leading-body: 1.8;
  --leading-title: 1.2;
  --tracking-title: -.02em;

  --r-pill: 999px;
  --r-circle: 50%;
  --r-win: 20px;
  --r-phone: 28px;
  --r-card: 28px;
  --r-group: 14px;
  --r-field: 11px;
  --r-item: 10px;
  --r-small: 8px;
  --r-tag: 7px;
  --r-medium: 12px;
  --r-icon: 16px;
  --r-list: 18px;

  --gutter: 24px;
  --width-content: 1200px;
  --width-reading: 800px;
  --width-header: 1440px;
  --space-section: 96px;
  --header-height: 72px;
  --duration-fast: .2s;
  --duration-normal: .25s;
  --duration-reveal: .6s;
  --ease: ease;
  --shadow-soft: 0 1px 2px var(--sh-tint-1), 0 6px 16px -8px var(--sh-tint-2);
  --shadow-win: 0 0 0 1px var(--c-border), 0 8px 0 0 var(--c-edge), 0 9px 0 0 var(--c-edge-deep), 0 18px 26px -12px var(--sh-tint-2), 0 44px 70px -26px var(--sh-tint-3), 0 90px 130px -50px var(--sh-tint-2);
  --shadow-phone: 0 0 0 1px var(--c-border), 0 7px 0 0 var(--c-edge), 0 8px 0 0 var(--c-edge-deep), -10px 20px 26px -12px var(--sh-tint-2), -26px 48px 72px -24px var(--sh-tint-3), -40px 80px 110px -40px var(--sh-tint-2);
  --shadow-menu: 0 0 0 1px var(--c-border), 0 2px 4px var(--sh-tint-1), 0 14px 28px -12px var(--sh-tint-3);
}

*, *::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;
  color: var(--c-ink);
  background: var(--c-panel);
  font-family: var(--font-body);
  font-size: var(--fs-body);
  line-height: var(--leading-body);
  -webkit-font-smoothing: antialiased;
  overflow-x: clip;
}
[hidden] { display: none !important; }
img, video, canvas { max-width: 100%; height: auto; }
svg { vertical-align: middle; flex-shrink: 0; }
button, input, select, textarea { font: inherit; }
button { cursor: pointer; }
button, a { -webkit-tap-highlight-color: var(--c-clear); }
a { color: inherit; text-underline-offset: .2em; }
a:hover { text-decoration-thickness: 2px; }
:focus-visible { outline: 2px solid var(--c-accent-dark); outline-offset: 4px; }
button:disabled, [aria-disabled="true"] { cursor: not-allowed; opacity: .5; }
h1, h2, h3, h4, p, ul, ol, figure, blockquote { margin-top: 0; }
h1, h2, h3, h4 {
  font-family: var(--font-display);
  line-height: var(--leading-title);
  letter-spacing: var(--tracking-title);
  text-wrap: balance;
}
h1 { font-size: var(--fs-h1); font-weight: var(--weight-display); }
h2 { font-size: var(--fs-h2); font-weight: var(--weight-display); }
h3 { font-size: var(--fs-h3); font-weight: var(--weight-heavy); }
p { margin-bottom: 1.2em; }
strong { font-weight: var(--weight-bold); }
small { font-size: var(--fs-xs); }
code, pre, kbd { font-family: var(--font-mono); }
code { overflow-wrap: anywhere; }
pre {
  max-width: 100%;
  overflow-x: auto;
  padding: 24px;
  border-radius: var(--r-group);
  background: var(--c-ink-card);
  color: var(--c-panel);
  font-size: var(--fs-sm);
  line-height: 1.7;
  overscroll-behavior-inline: contain;
}
pre code { overflow-wrap: normal; word-break: normal; white-space: pre; }
hr { border: 0; border-top: 1px solid var(--c-border); margin-block: 32px; }
.wrap {
  width: 100%;
  max-width: calc(var(--width-content) + var(--gutter) * 2);
  padding-inline: var(--gutter);
  margin-inline: auto;
}
.reading { max-width: calc(var(--width-reading) + var(--gutter) * 2); }
.section { padding-top: var(--space-section); padding-bottom: var(--space-section); }
.section-head { max-width: 760px; margin: 0 auto 40px; text-align: center; }
.section-head p, .muted { color: var(--c-muted); }
.section-head h2 { margin-bottom: 14px; }
.section-head p { font-size: var(--fs-lead); }
.grid { display: grid; gap: 24px; grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid > *, .wrap > *, .prose > *, .card > *, .panel > * { min-width: 0; }
.keep { white-space: nowrap; }
.icon { width: 20px; height: 20px; flex-shrink: 0; }
.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: 16px; z-index: 100;
  padding: 8px 16px; border-radius: var(--r-pill);
  background: var(--c-ink); color: var(--c-panel);
  transform: translateY(-150%);
}
.skip-link:focus { transform: none; }
.cta-row { display: flex; justify-content: center; flex-wrap: wrap; gap: 14px; margin-top: 26px; }
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 10px;
  min-height: 52px; padding: 0 28px; border: 0; border-radius: var(--r-pill);
  font-family: var(--font-body); font-size: var(--fs-body); font-weight: var(--weight-bold);
  text-decoration: none; line-height: 1.4;
  transition: transform var(--duration-fast) var(--ease), background var(--duration-fast) var(--ease);
}
.btn svg { width: 18px; height: 18px; flex: none; }
.btn:hover:not(:disabled):not([aria-disabled="true"]), .btn.is-hover { transform: translateY(-2px); }
.btn:active:not(:disabled), .btn.is-pressed { transform: translateY(1px); }
.btn-primary {
  background: var(--c-ink); color: var(--c-panel);
  box-shadow: 0 12px 24px -14px var(--sh-tint-3), 0 2px 0 var(--c-ink-soft);
}
.btn-ghost {
  background: var(--c-clear); color: var(--c-ink);
  box-shadow: inset 0 0 0 1.5px var(--c-ink);
}
.btn-ghost:hover { background: var(--c-glass); color: var(--c-ink); }
.btn.is-focus { outline: 2px solid var(--c-accent-dark); outline-offset: 4px; }
.pill-link {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  align-self: flex-start; min-height: 40px; padding: 8px 18px; margin-top: auto;
  border-radius: var(--r-pill); box-shadow: inset 0 0 0 1.5px currentColor;
  font-size: var(--fs-sm); font-weight: var(--weight-bold); text-decoration: none;
}
.pill-link svg { width: 14px; height: 14px; }
.card, .panel {
  padding: 32px; border-radius: var(--r-card);
  background: var(--c-panel-2); color: var(--c-ink); box-shadow: var(--shadow-soft);
}
.card h3, .panel h3 { margin-bottom: 12px; }
.card p:last-child, .panel p:last-child { margin-bottom: 0; }
.card--ink { background: var(--c-ink-card); color: var(--c-panel); }
.card--sky { background: var(--c-sky-card); color: var(--c-ink); }
.card--tomato { background: var(--c-accent-soft); color: var(--c-ink); }
.card--line { background: var(--c-panel); color: var(--c-ink); box-shadow: inset 0 0 0 1.5px var(--c-border); }
.card--ink .muted { color: var(--c-on-ink-muted); }
.prose { min-width: 0; }
.prose h2 { margin-top: 64px; margin-bottom: 24px; }
.prose h3 { margin-top: 32px; margin-bottom: 16px; }
.prose li + li { margin-top: 8px; }
.prose a { text-decoration-color: var(--c-muted); }
.prose :target { scroll-margin-top: 28px; }
.decorated { position: relative; overflow-x: clip; }
.reveal { opacity: 1; transform: none; }
.reveal.is-observed { opacity: 0; transform: translateY(16px); }
.reveal.shown {
  opacity: 1; transform: none;
  transition: opacity var(--duration-reveal) var(--ease), transform var(--duration-reveal) var(--ease);
}

/* 页头使用独立宽版心，不复用正文 .wrap。 */
#site-header { position: relative; z-index: 40; }
.topbar {
  position: relative; z-index: 40; display: flex; align-items: center; justify-content: space-between;
  gap: 28px; width: 100%; max-width: var(--width-header); height: var(--header-height);
  margin-inline: auto; padding-inline: 48px;
}
.brand { display: inline-flex; align-items: center; gap: 10px; flex-shrink: 0; text-decoration: none; }
.brand-mark { display: block; width: 34px; height: 34px; flex: none; }
.brand-name {
  font-family: var(--font-display); font-size: var(--fs-lead);
  font-weight: var(--weight-heavy); letter-spacing: -.015em;
}
.desktop-nav { margin-left: auto; min-width: 0; }
.tabs {
  display: flex; align-items: center; list-style: none; margin: 0; padding: 0; gap: 2px;
}
.tabs li { min-width: 0; }
.tabs a {
  position: relative; display: flex; align-items: center; height: var(--header-height);
  padding-inline: 13px; font-size: 15px; font-weight: var(--weight-medium);
  color: var(--c-ink); text-decoration: none; white-space: nowrap;
}
.tabs a::after {
  content: ""; position: absolute; left: 13px; right: 13px; bottom: 15px; height: 3px;
  border-radius: var(--r-pill); background: var(--c-accent);
  transform: scaleX(0); opacity: 0;
  transition: transform var(--duration-normal) var(--ease), opacity var(--duration-normal) var(--ease);
}
.tabs a:hover::after { transform: scaleX(.45); opacity: .45; }
.tabs a[aria-current="page"] { font-weight: var(--weight-bold); }
.tabs a[aria-current="page"]::after { transform: scaleX(1); opacity: 1; }
.header-tools { display: flex; align-items: center; gap: 12px; flex-shrink: 0; }
.language { position: relative; }
.lang {
  display: inline-flex; align-items: center; justify-content: center; gap: 7px;
  min-height: 38px; padding: 0 14px 0 12px; border: 0; border-radius: var(--r-pill);
  background: var(--c-glass); color: var(--c-ink);
  box-shadow: inset 0 0 0 1px var(--c-glass-line);
  font-size: var(--fs-sm); font-weight: var(--weight-semibold); text-decoration: none;
  white-space: nowrap;
}
.lang svg { width: 16px; height: 16px; }
.lang-short { display: none; }
.lang-caret { font-size: var(--fs-xs); color: var(--c-muted); }
.language-menu {
  position: absolute; right: 0; top: calc(100% + 10px); min-width: 180px;
  padding: 6px; margin: 0; list-style: none; border-radius: var(--r-group);
  background: var(--c-panel); color: var(--c-ink); box-shadow: var(--shadow-menu); z-index: 45;
}
.language-menu a { display: flex; align-items: center; min-height: 44px; padding: 8px 12px; text-decoration: none; border-radius: var(--r-item); }
.language-menu a:hover, .language-menu a[aria-current="true"] { background: var(--c-panel-2); color: var(--c-ink); }
.menu-toggle {
  display: none; align-items: center; justify-content: center; min-width: 44px; min-height: 44px;
  border: 1px solid var(--c-border); border-radius: var(--r-circle);
  background: var(--c-panel); color: var(--c-ink);
}
.menu-toggle svg { width: 22px; height: 22px; }
.nav-veil { position: fixed; inset: var(--header-height) 0 0; z-index: 38; border: 0; background: var(--c-veil); color: var(--c-ink); }
.mobile-drawer {
  position: absolute; top: 100%; left: var(--gutter); right: var(--gutter); z-index: 42;
  max-height: calc(100dvh - var(--header-height) - 16px); overflow-y: auto; overscroll-behavior: contain;
  padding: 12px; border-radius: var(--r-win); box-shadow: var(--shadow-menu);
  background: var(--c-panel); color: var(--c-ink);
}
.mobile-drawer ul { list-style: none; margin: 0; padding: 0; }
.mobile-drawer a {
  display: flex; align-items: center; width: 100%; min-height: 46px; padding: 10px 14px;
  border-radius: var(--r-item); text-decoration: none;
}
.mobile-drawer a:hover, .mobile-drawer a[aria-current] { background: var(--c-panel-2); color: var(--c-ink); }
.mobile-drawer a[aria-current="page"] { text-decoration: underline; text-decoration-color: var(--c-accent); text-decoration-thickness: 3px; }
.drawer-languages { border-top: 1px solid var(--c-border); margin-top: 12px; padding-top: 12px; }
.drawer-languages p { margin: 4px 14px; color: var(--c-muted); font-size: var(--fs-sm); }
.preview-mobile { display: none; position: relative; }
.preview-mobile > summary { list-style: none; cursor: pointer; }
.preview-mobile > nav { position: absolute; right: 0; top: 54px; width: min(280px, calc(100vw - 32px)); padding: 12px; background: var(--c-panel); color: var(--c-ink); border-radius: var(--r-group); box-shadow: var(--shadow-menu); }
.preview-mobile nav a { display: block; min-height: 44px; padding: 8px 12px; text-decoration: none; }

/* 页脚留出浮层的安全空间。 */
.site-footer { padding-top: 64px; padding-bottom: 100px; background: var(--c-panel-2); color: var(--c-ink); }
.footer-grid { display: grid; grid-template-columns: 1.4fr 1fr 1.2fr .8fr; gap: 40px; }
.footer-grid > * { min-width: 0; }
.footer-brand p { margin-top: 18px; max-width: 320px; color: var(--c-muted); font-size: var(--fs-sm); }
.footer-heading { margin-bottom: 14px; font-size: var(--fs-body); font-weight: var(--weight-bold); }
.footer-links { list-style: none; margin: 0; padding: 0; }
.footer-links a { display: inline-block; padding-block: 5px; font-size: var(--fs-sm); text-decoration: none; }
.footer-links a:hover { text-decoration: underline; }
.footer-bottom { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 16px; margin-top: 40px; padding-top: 24px; border-top: 1px solid var(--c-border); color: var(--c-muted); font-size: var(--fs-sm); }
.footer-bottom p { margin: 0; }

@media (max-width: 1360px) {
  .topbar { padding-inline: 28px; gap: 16px; }
  .tabs a { padding-inline: 9px; font-size: var(--fs-sm); }
  .tabs a::after { left: 9px; right: 9px; }
}
@media (max-width: 1279px) {
  .desktop-nav { display: none; }
  .header-tools { margin-left: auto; }
  .menu-toggle { display: inline-flex; }
  .preview-mobile { display: block; }
  .preview-mobile .menu-toggle { display: inline-flex; }
}
@media (min-width: 1280px) {
  .mobile-drawer, .nav-veil { display: none !important; }
}
@media (max-width: 900px) {
  .footer-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 32px; }
}
@media (max-width: 768px) {
  :root { --fs-h1: clamp(24px, 4vw, 30px); --space-section: 64px; }
  .grid { grid-template-columns: minmax(0, 1fr); }
}
@media (max-width: 640px) {
  :root { --gutter: 16px; }
  .wrap { padding-inline: var(--gutter); }
  .topbar { padding-inline: var(--gutter); gap: 8px; }
  .brand { gap: 7px; }
  .brand-name { font-size: var(--fs-sm); }
  .brand-mark { width: 30px; height: 30px; }
  .header-tools { gap: 8px; margin-left: auto; }
  .lang { min-height: 44px; padding-inline: 12px; }
  .lang-full { display: none; }
  .lang-short { display: inline; }
  .btn { min-height: 48px; padding-inline: 22px; font-size: 15px; }
  .card, .panel { padding: 24px; }
  .tilt, [data-tilt] { transform: none !important; }
  .footer-grid { grid-template-columns: minmax(0, 1fr); }
  .footer-brand p { max-width: none; }
  pre { padding: 18px; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition: none !important; animation: none !important; }
  .reveal.is-observed { opacity: 1; transform: none; }
}