:root {
  --accent: #4F8CFF;
  --accent2: #7C5CFF;
  --bg: #0B0E14;
  --bg2: #11161F;
  --card: #151B26;
  --line: rgba(255,255,255,.09);
  --tx: #E9EDF5;
  --tx2: #9BA6B8;
  --radius: 16px;
  --wrap: 1120px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--tx);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", sans-serif;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; text-decoration: none; }

.wrap {
  width: 100%;
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 0 24px;
}

.wrap.narrow { max-width: 760px; }
.center { text-align: center; }

.skip {
  position: absolute;
  left: -9999px;
}
.skip:focus {
  left: 16px; top: 16px;
  z-index: 99;
  background: var(--accent);
  color: #fff;
  padding: 10px 16px;
  border-radius: 8px;
}

/* ---------- nav ---------- */
.nav {
  position: sticky;
  top: 0;
  z-index: 20;
  backdrop-filter: saturate(160%) blur(14px);
  background: rgba(11,14,20,.78);
  border-bottom: 1px solid var(--line);
}
.nav-in {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 66px;
  gap: 20px;
}
.logo { display: flex; align-items: center; gap: 10px; }
.logo-mark {
  width: 22px; height: 22px;
  border-radius: 7px;
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  box-shadow: 0 0 0 1px rgba(255,255,255,.14) inset;
}
.logo-text { font-weight: 650; letter-spacing: .2px; }
.nav nav { display: flex; align-items: center; gap: 8px; }
.nav nav a {
  padding: 8px 14px;
  border-radius: 10px;
  color: var(--tx2);
  font-size: 14.5px;
  transition: color .18s, background .18s;
}
.nav nav a:hover { color: var(--tx); background: rgba(255,255,255,.05); }

/* ---------- buttons ---------- */
.btn {
  display: inline-block;
  padding: 11px 22px;
  border-radius: 12px;
  font-size: 15px;
  font-weight: 560;
  border: 1px solid transparent;
  transition: transform .16s, border-color .18s, background .18s;
}
.btn:hover { transform: translateY(-1px); }
.btn-primary {
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  color: #fff;
}
.btn-ghost {
  border-color: var(--line);
  color: var(--tx);
}
.btn-ghost:hover { border-color: var(--accent); }
.btn-nav {
  border-color: rgba(255,255,255,.16);
  color: var(--tx) !important;
  padding: 8px 16px;
}
.btn-nav:hover { border-color: var(--accent); background: transparent !important; }

/* ---------- hero ---------- */
.hero {
  position: relative;
  padding: 108px 0 84px;
  overflow: hidden;
}
.hero::before {
  content: "";
  position: absolute;
  inset: -30% 20% auto -10%;
  height: 560px;
  background: radial-gradient(46% 46% at 30% 40%, color-mix(in srgb, var(--accent) 26%, transparent), transparent 70%);
  filter: blur(20px);
  pointer-events: none;
}
.hero .wrap { position: relative; }
.kicker {
  margin: 0 0 18px;
  font-size: 12.5px;
  letter-spacing: 2.4px;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 620;
}
.hero h1 {
  margin: 0 0 20px;
  font-size: clamp(34px, 5.4vw, 58px);
  line-height: 1.18;
  letter-spacing: -.5px;
  font-weight: 700;
}
.lede {
  margin: 0 0 32px;
  max-width: 620px;
  font-size: clamp(16px, 1.5vw, 18.5px);
  color: var(--tx2);
}
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; }
.hero-note {
  margin: 28px 0 0;
  font-size: 13px;
  color: var(--tx2);
  opacity: .8;
}

/* ---------- sections ---------- */
.section { padding: 78px 0; border-top: 1px solid var(--line); }
.section-alt { background: var(--bg2); }
.section h2 {
  margin: 0 0 34px;
  font-size: clamp(24px, 2.9vw, 34px);
  letter-spacing: -.3px;
  font-weight: 680;
}
.section p { color: var(--tx2); font-size: 16px; }
.section code {
  background: rgba(255,255,255,.07);
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 1px 6px;
  font-size: 13.5px;
  color: var(--tx);
}

/* ---------- cards ---------- */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(272px, 1fr));
  gap: 18px;
}
.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 26px 24px;
  transition: border-color .2s, transform .2s;
}
.card:hover { border-color: color-mix(in srgb, var(--accent) 55%, var(--line)); transform: translateY(-2px); }
.card h3 {
  margin: 0 0 12px;
  font-size: 18px;
  font-weight: 640;
}
.card p { margin: 0; color: var(--tx2); font-size: 15px; }

/* ---------- footer ---------- */
.foot {
  border-top: 1px solid var(--line);
  background: var(--bg2);
  padding: 54px 0 0;
}
.foot-in {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr;
  gap: 36px;
}
.foot-brand { margin: 0 0 6px; font-weight: 660; font-size: 17px; }
.foot-tag { margin: 0; color: var(--tx2); font-size: 14px; }
.foot-h {
  margin: 0 0 12px;
  font-size: 12.5px;
  letter-spacing: 1.4px;
  text-transform: uppercase;
  color: var(--tx2);
  font-weight: 620;
}
.foot ul { margin: 0; padding: 0; list-style: none; }
.foot li { margin-bottom: 9px; }
.foot li a { color: var(--tx2); font-size: 14px; transition: color .18s; }
.foot li a:hover { color: var(--accent); }
.foot-bot {
  margin-top: 44px;
  padding: 20px 24px 26px;
  border-top: 1px solid var(--line);
}
.foot-bot p { margin: 0; color: var(--tx2); font-size: 13px; opacity: .85; }

/* ---------- hub: clusters & guide cards ---------- */
.cluster { margin-bottom: 46px; }
.cluster:last-child { margin-bottom: 0; }
.cluster > h3 {
  margin: 0 0 16px;
  font-size: 13px;
  letter-spacing: 1.6px;
  text-transform: uppercase;
  color: var(--tx2);
  font-weight: 620;
}
.card.guide { display: block; }
.card.guide h3 { margin: 0 0 10px; font-size: 16.5px; line-height: 1.4; }
.card.guide p { font-size: 14.5px; line-height: 1.65; }

/* ---------- article layout ---------- */
.post { max-width: 860px; padding-top: 34px; padding-bottom: 40px; }
.crumbs {
  font-size: 13px;
  color: var(--tx2);
  margin: 0 0 22px;
  display: flex;
  gap: 8px;
  align-items: center;
  flex-wrap: wrap;
}
.crumbs a { color: var(--accent); }
.crumbs a:hover { text-decoration: underline; }
.post-head { margin-bottom: 26px; }
.post-head h1 {
  margin: 0 0 14px;
  font-size: clamp(26px, 3.6vw, 40px);
  line-height: 1.22;
  letter-spacing: -.4px;
  font-weight: 700;
  max-width: 780px;
}
.meta-row { margin: 14px 0 0; font-size: 13px; color: var(--tx2); }
.meta-row a { color: var(--accent); }

/* ---------- TOC ---------- */
.toc {
  border: 1px solid var(--line);
  background: var(--card);
  border-radius: 14px;
  padding: 16px 20px;
  margin: 0 0 28px;
}
.toc-t {
  margin: 0 0 10px;
  font-size: 12px;
  letter-spacing: 1.4px;
  text-transform: uppercase;
  color: var(--tx2);
  font-weight: 620;
}
.toc ul {
  margin: 0; padding: 0; list-style: none;
  display: grid; gap: 6px;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
}
.toc a { color: var(--tx2); font-size: 14px; transition: color .18s; }
.toc a:hover { color: var(--accent); }

/* ---------- prose ---------- */
.prose { font-size: 16.5px; line-height: 1.85; color: var(--tx); }
.prose p { margin: 0 0 20px; }
.prose h2, .post-sec h2 {
  margin: 46px 0 18px;
  font-size: clamp(21px, 2.6vw, 27px);
  letter-spacing: -.2px;
  font-weight: 680;
  scroll-margin-top: 90px;
}
.prose h2:first-child { margin-top: 0; }
.prose h3 { margin: 30px 0 12px; font-size: 18px; font-weight: 640; }
.prose ul, .prose ol { margin: 0 0 22px; padding-left: 22px; }
.prose li { margin-bottom: 9px; }
.prose li::marker { color: var(--accent); }
.prose strong { color: #fff; font-weight: 640; }
.prose a { color: var(--accent); border-bottom: 1px solid transparent; transition: border-color .18s; }
.prose a:hover { border-bottom-color: var(--accent); }

/* ---------- tables ---------- */
.tbl-wrap {
  overflow-x: auto;
  margin: 0 0 24px;
  border: 1px solid var(--line);
  border-radius: 14px;
}
.prose table { width: 100%; border-collapse: collapse; font-size: 14.5px; min-width: 520px; }
.prose th {
  text-align: left;
  padding: 12px 16px;
  background: var(--bg2);
  color: var(--tx2);
  font-size: 12.5px;
  letter-spacing: 1px;
  text-transform: uppercase;
  font-weight: 620;
  border-bottom: 1px solid var(--line);
}
.prose td { padding: 12px 16px; border-bottom: 1px solid var(--line); color: var(--tx); vertical-align: top; }
.prose tbody tr:last-child td { border-bottom: none; }
.prose tbody tr:hover td { background: rgba(255,255,255,.02); }

/* ---------- callouts ---------- */
.callout {
  border-radius: 14px;
  padding: 18px 20px 16px;
  margin: 0 0 24px;
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent);
  background: color-mix(in srgb, var(--accent) 7%, var(--card));
}
.callout.warn { border-left-color: #FF5C7A; background: color-mix(in srgb, #FF5C7A 7%, var(--card)); }
.callout.tip { border-left-color: #2BD9A8; background: color-mix(in srgb, #2BD9A8 7%, var(--card)); }
.callout-t { margin: 0 0 8px; font-weight: 640; color: var(--tx); font-size: 15px; }
.callout p { font-size: 14.5px; line-height: 1.7; color: var(--tx2); }
.callout p:last-child { margin: 0; }

/* ---------- sources box ---------- */
.srcbox {
  border: 1px dashed var(--line);
  border-radius: 14px;
  padding: 16px 20px;
  margin: 8px 0 0;
  background: var(--bg2);
}
.srcbox ul { margin: 0; padding: 0; list-style: none; }
.srcbox li { margin-bottom: 8px; font-size: 14px; }
.srcbox li:last-child { margin-bottom: 0; }
.srcbox a { color: var(--accent); }
.srcbox .callout-t { margin-bottom: 10px; }

/* ---------- FAQ accordion ---------- */
.faq {
  border: 1px solid var(--line);
  border-radius: 14px;
  background: var(--card);
  margin-bottom: 12px;
  overflow: hidden;
}
.faq summary {
  cursor: pointer;
  padding: 15px 20px;
  font-weight: 600;
  font-size: 15.5px;
  list-style: none;
  position: relative;
  padding-right: 44px;
  transition: background .18s;
}
.faq summary:hover { background: rgba(255,255,255,.03); }
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after {
  content: "+";
  position: absolute;
  right: 18px; top: 50%;
  transform: translateY(-50%);
  font-size: 20px;
  color: var(--accent);
  font-weight: 500;
}
.faq[open] summary::after { content: "−"; }
.faq p { margin: 0; padding: 0 20px 16px; color: var(--tx2); font-size: 14.5px; line-height: 1.75; }

/* ---------- related & post nav ---------- */
.rel-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 14px; }
.rel-card {
  display: block;
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 16px 18px;
  background: var(--card);
  transition: border-color .2s, transform .2s;
}
.rel-card:hover { border-color: color-mix(in srgb, var(--accent) 55%, var(--line)); transform: translateY(-2px); }
.rel-k {
  display: block;
  font-size: 11.5px;
  letter-spacing: 1.2px;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 620;
  margin-bottom: 7px;
}
.rel-t { font-size: 14.5px; line-height: 1.5; color: var(--tx); font-weight: 560; }
.post-nav { display: flex; justify-content: space-between; gap: 12px; flex-wrap: wrap; margin-top: 44px; }

/* ---------- language switcher ---------- */
.lang { position: relative; display: inline-block; }
.lang-btn {
  display: inline-flex; align-items: center; gap: 7px;
  background: rgba(255,255,255,.04);
  border: 1px solid var(--line);
  color: var(--tx2);
  font: inherit; font-size: 13.5px; font-weight: 560;
  padding: 7px 11px; border-radius: 9px; cursor: pointer;
  transition: border-color .15s, color .15s, background .15s;
}
.lang-btn:hover, .lang:focus-within .lang-btn {
  color: var(--tx); border-color: rgba(79,140,255,.45); background: rgba(255,255,255,.06);
}
.lang-globe {
  width: 14px; height: 14px; flex: 0 0 14px; border-radius: 50%;
  border: 1.4px solid currentColor; position: relative;
}
.lang-globe::before, .lang-globe::after {
  content: ""; position: absolute; inset: 0; border: 1.4px solid currentColor;
  border-radius: 50%;
}
.lang-globe::before { border-width: 0 1.4px; border-radius: 50%; transform: scaleX(.45); }
.lang-globe::after { border-width: 1.4px 0; border-radius: 0; transform: scaleY(.0); top: 50%; }
.lang-caret {
  width: 0; height: 0; margin-left: 1px;
  border-left: 4px solid transparent; border-right: 4px solid transparent;
  border-top: 5px solid currentColor; opacity: .7;
}
.lang-menu {
  position: absolute; top: calc(100% + 8px); right: 0; z-index: 60;
  min-width: 190px; max-height: 62vh; overflow-y: auto;
  list-style: none; margin: 0; padding: 6px;
  background: var(--card);
  border: 1px solid var(--line); border-radius: 12px;
  box-shadow: 0 18px 44px rgba(0,0,0,.5);
  opacity: 0; visibility: hidden; transform: translateY(-4px);
  transition: opacity .15s, transform .15s, visibility .15s;
}
.lang.open .lang-menu, .lang:focus-within .lang-menu {
  opacity: 1; visibility: visible; transform: translateY(0);
}
.lang-menu .lang-opt {
  display: block; padding: 8px 11px; border-radius: 8px;
  font-size: 13.5px; color: var(--tx2); text-decoration: none;
  white-space: nowrap;
}
.lang-menu .lang-opt:hover { background: rgba(255,255,255,.06); color: var(--tx); }
.lang-menu .lang-opt.active { color: var(--accent); font-weight: 620; }

@media (max-width: 760px) {
  .post { padding-top: 24px; }
  .toc ul { grid-template-columns: 1fr; }
  .post-nav { flex-direction: column; }
  .post-nav .btn { text-align: center; }
  .lang-menu { right: auto; left: 0; }
}

@media (max-width: 760px) {
  .foot-in { grid-template-columns: 1fr; gap: 28px; }
  .nav nav a:not(.btn) { display: none; }
  .hero { padding: 76px 0 60px; }
  .section { padding: 58px 0; }
}

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; scroll-behavior: auto !important; }
}