:root {
  --c-bg: #FFFFFF;
  --c-panel: #F5F8FC;
  --c-panel-2: #EAF1FB;
  --c-border: #DCE4EF;
  --c-border-strong: #BFCCDD;
  --c-accent: #0B6BFF;
  --c-accent-dark: #004AC9;
  --c-accent-line: #A9C8FF;
  --c-ink: #0C2A4D;
  --c-muted: #52677F;
  --c-success: #13A56C;
  --c-success-soft: rgba(19, 165, 108, 0.16);
  --c-warn: #E39A0C;
  --c-error: #DF3B3F;
  --c-white: #FFFFFF;
  --c-ghost: rgba(255, 255, 255, 0.62);
  --c-ghost-edge: rgba(255, 255, 255, 0.85);
  --c-sky: #1FA8FF;
  --c-orchid: #C640F2;
  --c-orchid-light: #E25BFF;
  --c-veil: rgba(12, 42, 77, 0.28);
  --c-clear: transparent;
  --shadow-float: 0 30px 80px rgba(34, 64, 104, 0.08), 0 4px 14px rgba(34, 64, 104, 0.05);
  --shadow-back: 0 18px 50px rgba(34, 64, 104, 0.06);
  --shadow-btn: 0 10px 24px rgba(11, 107, 255, 0.24);
  --shadow-chip: 0 1px 2px rgba(34, 64, 104, 0.06);
  --shadow-cursor: drop-shadow(0 2px 3px rgba(12, 42, 77, 0.28));
  --r-float: 28px;
  --r-card: 20px;
  --r-btn: 12px;
  --r-field: 10px;
  --r-small: 8px;
  --r-tile: 9px;
  --r-pill: 999px;
  --r-circle: 50%;
  --font-display: "Inter", "Noto Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
  --font-body: "Inter", "Noto Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, -apple-system, "Segoe UI", sans-serif;
  --font-mono: "JetBrains Mono", ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
  --weight-normal: 400;
  --weight-medium: 500;
  --weight-semibold: 600;
  --weight-bold: 700;
  --weight-heavy: 800;
  --weight-display: 900;
  --size-body: 16px;
  --size-small: 14px;
  --size-lead: 17px;
  --size-h1: clamp(34px, 1.2rem + 2.2vw, 48px);
  --size-h2: clamp(26px, 1rem + 1.8vw, 40px);
  --size-h3: 22px;
  --topbar-h: 72px;
  --wrap: 1320px;
  --read-wrap: 880px;
  --gutter: 48px;
  --section-space: 96px;
  --ease-ui: 180ms ease;
  --ease-reveal: 650ms cubic-bezier(0.2, 0.7, 0.2, 1);
}

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; scroll-padding-top: calc(var(--topbar-h) + 24px); }
html.nav-open { overflow: hidden; }
body {
  margin: 0;
  background: var(--c-bg);
  color: var(--c-ink);
  font-family: var(--font-body);
  font-size: var(--size-body);
  font-weight: var(--weight-normal);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}
[hidden] { display: none !important; }
img { display: block; max-width: 100%; height: auto; }
svg { display: block; flex-shrink: 0; }
button, input, select, textarea { font: inherit; }
button { cursor: pointer; }
button, a, input, select, textarea { -webkit-tap-highlight-color: var(--c-clear); }
a { color: inherit; text-decoration: none; }
p { margin: 0; }
ul, ol { margin-top: 0; }
button { color: var(--c-ink); }
:focus-visible { outline: 2px solid var(--c-accent); outline-offset: 3px; border-radius: var(--r-small); }
::selection { background: var(--c-panel-2); color: var(--c-ink); }
h1, h2, h3, h4 { margin-top: 0; font-family: var(--font-display); color: var(--c-ink); text-wrap: balance; }
h1 { font-size: var(--size-h1); font-weight: var(--weight-display); line-height: 1.14; letter-spacing: -0.02em; }
h2 { font-size: var(--size-h2); font-weight: var(--weight-display); line-height: 1.2; letter-spacing: -0.02em; }
h3 { font-size: var(--size-h3); font-weight: var(--weight-heavy); line-height: 1.35; }
h4 { font-size: var(--size-body); font-weight: var(--weight-bold); }
strong { font-weight: var(--weight-bold); }
code, kbd, samp, pre { font-family: var(--font-mono); }
code { overflow-wrap: anywhere; }
pre {
  max-width: 100%;
  min-width: 0;
  margin: 24px 0;
  padding: 22px;
  overflow-x: auto;
  background: var(--c-panel);
  color: var(--c-ink);
  border: 1px solid var(--c-border);
  border-radius: var(--r-card);
  font-size: var(--size-small);
  line-height: 1.75;
  tab-size: 2;
}
pre code { overflow-wrap: normal; word-break: normal; white-space: pre; }
hr { border: 0; border-top: 1px solid var(--c-border); margin: 32px 0; }
.wrap, .reading-wrap {
  width: 100%;
  max-width: var(--wrap);
  margin-inline: auto;
  padding-inline: var(--gutter);
}
.reading-wrap { max-width: calc(var(--read-wrap) + var(--gutter) * 2); }
.section { padding-top: var(--section-space); padding-bottom: var(--section-space); }
.section-head { margin-bottom: 48px; text-align: center; }
.section-title { margin: 0 0 18px; font-size: var(--size-h2); font-weight: var(--weight-display); line-height: 1.2; letter-spacing: -0.02em; }
.section-lead { max-width: 40em; margin-inline: auto; font-size: var(--size-lead); line-height: 1.75; color: var(--c-muted); }
.word { white-space: nowrap; }
.muted { color: var(--c-muted); }
.mono { font-family: var(--font-mono); }
.text-link { color: var(--c-accent-dark); text-decoration: underline; text-underline-offset: 4px; }
.text-link:hover { color: var(--c-ink); }
.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(-160%); }
.skip-link:focus { transform: none; }
.grid { display: grid; gap: 24px; }
.grid--two { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid--three { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.grid > *, .hero__inner > *, .win__body > *, .footer-grid > *, .feature-tabs > * { min-width: 0; }
.stack-flow > * + * { margin-top: 20px; }
.card, .panel {
  min-width: 0;
  padding: 28px;
  background: var(--c-bg);
  color: var(--c-ink);
  border: 1px solid var(--c-border);
  border-radius: var(--r-card);
}
.card--raised { box-shadow: var(--shadow-float); }
.panel { background: var(--c-panel); color: var(--c-ink); }
.panel--second { background: var(--c-panel-2); color: var(--c-ink); }
.card h3, .panel h3 { margin-bottom: 12px; }
.card p, .panel p { color: var(--c-muted); }
.prose { min-width: 0; line-height: 1.9; }
.prose p, .prose ul, .prose ol { margin-bottom: 20px; }
.prose h2 { margin-top: 60px; margin-bottom: 24px; }
.prose h3 { margin-top: 32px; margin-bottom: 16px; }
.prose a:not(.btn) { color: var(--c-accent-dark); text-decoration: underline; text-underline-offset: 3px; }
.prose li + li { margin-top: 8px; }
.prose :not(pre) > code { background: var(--c-panel); color: var(--c-ink); border-radius: var(--r-small); padding: 2px 5px; font-size: 0.9em; }
.decorated, .hero, .geometry-tray { position: relative; overflow-x: clip; }
.reveal { opacity: 1; transform: none; }
.reveal.reveal-ready { opacity: 0; transform: translateY(16px); transition: opacity var(--ease-reveal), transform var(--ease-reveal); }
.reveal.shown { opacity: 1; transform: none; }

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 9px;
  min-height: 54px;
  max-width: 100%;
  padding: 12px 26px;
  border: 1px solid var(--c-clear);
  border-radius: var(--r-btn);
  font-family: var(--font-body);
  font-size: var(--size-body);
  font-weight: var(--weight-bold);
  line-height: 1.4;
  letter-spacing: -0.005em;
  text-align: center;
  transition: background-color var(--ease-ui), border-color var(--ease-ui), color var(--ease-ui);
}
.btn svg { width: 19px; height: 19px; }
.btn--primary { background: var(--c-accent); color: var(--c-white); box-shadow: var(--shadow-btn); }
.btn--primary:hover, .btn--primary.is-hover { background: var(--c-accent-dark); color: var(--c-white); }
.btn--primary:active, .btn--primary.is-active { background: var(--c-accent-dark); color: var(--c-white); box-shadow: none; }
.btn--ghost { background: var(--c-bg); color: var(--c-ink); border-color: var(--c-border); box-shadow: var(--shadow-chip); }
.btn--ghost:hover, .btn--ghost.is-hover { border-color: var(--c-accent); color: var(--c-accent-dark); }
.btn--small { min-height: 44px; padding: 10px 18px; font-size: var(--size-small); }
.btn:disabled, .btn[aria-disabled="true"] { background: var(--c-panel-2); color: var(--c-muted); border-color: var(--c-border); box-shadow: none; cursor: not-allowed; }
.btn.is-focus { outline: 2px solid var(--c-accent); outline-offset: 3px; }
.action-row { display: flex; flex-wrap: wrap; align-items: center; gap: 12px; }

#site-header, .topbar { position: sticky; top: 0; z-index: 40; height: var(--topbar-h); background: var(--c-bg); color: var(--c-ink); border-bottom: 1px solid var(--c-border); }
.topbar__inner {
  max-width: min(100%, calc(1280px + var(--gutter) * 2));
  height: 100%;
  margin-inline: auto;
  padding-inline: var(--gutter);
  display: flex;
  align-items: center;
  gap: 28px;
}
.brand { display: inline-flex; align-items: center; gap: 11px; flex-shrink: 0; }
.brand__mark { width: 36px; height: 36px; flex-shrink: 0; }
.brand__name { font-family: var(--font-display); font-weight: var(--weight-heavy); font-size: 18px; letter-spacing: -0.02em; color: var(--c-ink); }
.mainnav { margin-left: auto; min-width: 0; }
.mainnav__list { display: flex; align-items: center; list-style: none; margin: 0; padding: 0; gap: 2px; }
.mainnav__link { display: inline-flex; align-items: center; min-height: 38px; padding: 0 14px; border-radius: var(--r-pill); font-size: 14.5px; font-weight: var(--weight-medium); color: var(--c-muted); white-space: nowrap; transition: background-color var(--ease-ui), color var(--ease-ui); }
.mainnav__link:hover { background: var(--c-panel); color: var(--c-ink); }
.mainnav__link[aria-current="page"] { background: var(--c-panel-2); color: var(--c-accent-dark); font-weight: var(--weight-bold); }
.header-tools { display: flex; align-items: center; gap: 10px; flex-shrink: 0; }
.language-picker { position: relative; }
.lang { display: inline-flex; align-items: center; justify-content: center; gap: 7px; min-height: 40px; padding: 0 14px; border: 1px solid var(--c-border); border-radius: var(--r-btn); background: var(--c-bg); color: var(--c-ink); font-size: var(--size-small); font-weight: var(--weight-medium); white-space: nowrap; }
.lang svg { width: 16px; height: 16px; color: var(--c-muted); }
.lang__caret { color: var(--c-muted); font-size: 11px; }
.lang__short { display: none; }
.language-menu { position: absolute; top: calc(100% + 10px); right: 0; z-index: 46; min-width: 184px; padding: 8px; list-style: none; margin: 0; border: 1px solid var(--c-border); border-radius: var(--r-card); background: var(--c-bg); color: var(--c-ink); box-shadow: var(--shadow-float); }
.language-menu a { display: flex; align-items: center; min-height: 44px; padding: 10px 14px; border-radius: var(--r-btn); }
.language-menu a:hover, .language-menu a[aria-current="true"] { background: var(--c-panel-2); color: var(--c-accent-dark); }
.menu-toggle { display: none; align-items: center; justify-content: center; min-width: 44px; min-height: 44px; padding: 10px; border: 1px solid var(--c-border); border-radius: var(--r-btn); background: var(--c-bg); color: var(--c-ink); }
.menu-toggle svg { width: 22px; height: 22px; }
.menu-toggle[aria-expanded="true"] .menu-toggle__bars { display: none; }
.menu-toggle .menu-toggle__cross { display: none; }
.menu-toggle[aria-expanded="true"] .menu-toggle__cross { display: block; }
.mobile-drawer { display: none; }
.nav-veil { position: fixed; inset: var(--topbar-h) 0 0; z-index: 41; border: 0; padding: 0; background: var(--c-veil); color: var(--c-ink); }
.topbar__inner > .brand, .header-tools { position: relative; z-index: 43; }

.footer { margin-top: 64px; padding-top: 64px; padding-bottom: 100px; border-top: 1px solid var(--c-border); background: var(--c-bg); color: var(--c-ink); }
.footer-grid { display: grid; grid-template-columns: 1.2fr 0.8fr 1.2fr; gap: 48px; }
.footer-brand p { max-width: 28em; margin-top: 20px; color: var(--c-muted); font-size: var(--size-small); line-height: 1.9; }
.footer-heading { margin-bottom: 18px; font-size: var(--size-small); font-weight: var(--weight-bold); }
.footer-links { display: grid; gap: 10px; margin: 0; padding: 0; list-style: none; font-size: var(--size-small); color: var(--c-muted); }
.footer-links a { display: inline-block; padding-block: 4px; }
.footer a:hover { color: var(--c-accent-dark); }
.footer-bottom { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 20px; margin-top: 48px; padding-top: 24px; border-top: 1px solid var(--c-border); color: var(--c-muted); font-size: var(--size-small); }
.footer-languages { display: flex; flex-wrap: wrap; gap: 8px 20px; }
.footer-languages a { padding-block: 8px; }
.footer-languages [aria-current="true"] { color: var(--c-accent-dark); }

@media (max-width: 1360px) {
  .topbar__inner { gap: 18px; }
  .mainnav__link { padding-inline: 10px; font-size: var(--size-small); }
}
@media (max-width: 1279px) {
  .mainnav { display: none; }
  .header-tools { margin-left: auto; }
  .menu-toggle { display: inline-flex; }
  .mobile-drawer:not([hidden]) { display: block; position: absolute; z-index: 44; top: var(--topbar-h); left: 0; right: 0; max-height: calc(100vh - var(--topbar-h)); max-height: calc(100dvh - var(--topbar-h)); padding: 16px var(--gutter) 28px; overflow-y: auto; overscroll-behavior: contain; background: var(--c-bg); color: var(--c-ink); border-bottom: 1px solid var(--c-border); box-shadow: var(--shadow-back); }
  .mobile-drawer ul { display: grid; gap: 4px; 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-btn); color: var(--c-muted); }
  .mobile-drawer a:hover, .mobile-drawer a[aria-current] { background: var(--c-panel-2); color: var(--c-accent-dark); }
  .drawer-languages { margin-top: 18px; padding-top: 18px; border-top: 1px solid var(--c-border); }
  .drawer-languages p { margin-bottom: 8px; padding-inline: 16px; color: var(--c-muted); font-size: var(--size-small); }
}
@media (max-width: 1080px) {
  :root { --gutter: 28px; --section-space: 72px; }
  .grid--three { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .footer-grid { gap: 28px; grid-template-columns: 1fr 1fr; }
  .footer-brand { grid-column: 1 / -1; }
}
@media (max-width: 768px) {
  h1 { font-size: clamp(24px, 4vw, 30px); }
}
@media (max-width: 640px) {
  :root { --gutter: 18px; --section-space: 56px; --size-h3: 20px; }
  .brand__name { font-size: var(--size-body); }
  .topbar__inner { gap: 10px; }
  .brand { gap: 8px; }
  .brand__mark { width: 32px; height: 32px; }
  .header-tools { margin-left: auto; gap: 6px; }
  .lang { min-height: 44px; padding-inline: 10px; }
  .lang__full { display: none; }
  .lang__short { display: inline; }
  .lang > svg { display: none; }
  .grid--two, .grid--three { grid-template-columns: minmax(0, 1fr); }
  .card, .panel { padding: 22px; }
  .section-lead { font-size: 15.5px; }
  .section-head { margin-bottom: 32px; }
  .btn { min-height: 50px; padding-inline: 20px; font-size: 15px; }
  .btn--small { min-height: 44px; }
  .tilt, .stack, [data-tilt] { transform: none !important; }
  .footer-grid { grid-template-columns: minmax(0, 1fr); gap: 32px; }
  .footer-brand { grid-column: auto; }
  .footer-bottom { align-items: flex-start; flex-direction: column; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation: none !important; transition: none !important; }
  .reveal.reveal-ready { opacity: 1; transform: none; }
}