:root {
  --bg: #0b0f14;
  --surface: #141a22;
  --elevated: #1b2330;
  --border: #2a3340;
  --text: #f4f7fa;
  --secondary: #9aa4b2;
  --muted: #6b7380;
  --cyan: #22d3ee;
  --cyan-dim: #0e7490;
  --amber: #f5b942;
  --amber-dim: #b45309;
  --card-cyan: #173f51;
  --shell: 880px;
  --font: "Noto Sans SC", "PingFang SC", "Hiragino Sans GB", sans-serif;
  --display: "Oxanium", "Noto Sans SC", sans-serif;
}

*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  min-height: 100vh;
  color: var(--secondary);
  background: var(--bg);
  font: 15px/1.8 var(--font);
  -webkit-font-smoothing: antialiased;
}
::selection { background: rgba(34, 211, 238, 0.28); color: var(--text); }

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  background:
    radial-gradient(ellipse 80% 50% at 8% -8%, rgba(34, 211, 238, 0.18), transparent 55%),
    radial-gradient(ellipse 55% 40% at 100% 0%, rgba(245, 185, 66, 0.08), transparent 50%),
    radial-gradient(ellipse 50% 35% at 70% 110%, rgba(14, 116, 144, 0.16), transparent 45%);
}
body::after {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  opacity: 0.4;
  background-image:
    linear-gradient(rgba(42, 51, 64, 0.55) 1px, transparent 1px),
    linear-gradient(90deg, rgba(42, 51, 64, 0.55) 1px, transparent 1px);
  background-size: 56px 56px;
  mask-image: radial-gradient(ellipse 75% 60% at 50% 20%, #000 15%, transparent 75%);
}

a { color: var(--cyan); text-decoration: none; }
a:hover { color: #7ee7f7; }

.read-progress {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: 2px;
  z-index: 40;
  background: linear-gradient(90deg, var(--cyan), var(--amber));
  transform: scaleX(0);
  transform-origin: 0 50%;
}

.bar {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 14px 24px;
  border-bottom: 1px solid var(--border);
  background: rgba(11, 15, 20, 0.82);
  backdrop-filter: blur(16px);
}
.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--text);
  font-family: var(--display);
  font-weight: 700;
  letter-spacing: 0.04em;
}
.brand i {
  width: 28px; height: 28px;
  border: 1px solid var(--cyan);
  border-radius: 8px;
  display: grid;
  place-items: center;
  color: var(--cyan);
  font-style: normal;
  font-size: 11px;
}
.bar nav { display: flex; flex-wrap: wrap; gap: 8px 16px; font-size: 13px; }
.bar nav a { color: var(--secondary); }
.bar nav a[aria-current="page"], .bar nav a:hover { color: var(--text); }

.wrap { position: relative; z-index: 1; max-width: var(--shell); margin: 0 auto; padding: 40px 24px 80px; }

.doc-head h1 {
  margin: 0 0 8px;
  color: var(--text);
  font-family: var(--display);
  font-size: clamp(28px, 4vw, 40px);
  letter-spacing: 0.02em;
}
.meta { color: var(--muted); font-size: 13px; margin-bottom: 32px; }
.meta span + span::before { content: " · "; }

.toc {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 8px;
  margin: 0 0 40px;
  padding: 16px;
  border: 1px solid var(--border);
  border-radius: 16px;
  background: var(--surface);
  font-size: 13px;
}
.toc strong { grid-column: 1 / -1; color: var(--cyan); font-size: 11px; letter-spacing: 0.16em; text-transform: uppercase; }
.toc a { color: var(--secondary); }
.toc a:hover { color: var(--text); }

article h2 {
  margin: 40px 0 12px;
  color: var(--text);
  font-size: 18px;
  font-weight: 700;
}
article p, article li { color: var(--secondary); }
article ol, article ul { padding-left: 1.2em; }
article li { margin: 6px 0; }
article strong { color: var(--text); }
.warn {
  margin: 16px 0;
  padding: 14px 16px;
  border-radius: 14px;
  border: 1px solid rgba(245, 185, 66, 0.35);
  background: rgba(79, 51, 35, 0.45);
  color: #f3d9a4;
}
.foot {
  margin-top: 56px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 12px;
}

/* homepage */
.home .wrap { max-width: 1080px; }
.hero {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 48px;
  align-items: center;
  min-height: 72vh;
  padding: 32px 0 24px;
}
.kicker {
  color: var(--cyan);
  font-family: var(--display);
  font-size: 12px;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  margin: 0 0 16px;
}
.hero h1 {
  margin: 0;
  color: var(--text);
  font-family: var(--display);
  font-size: clamp(40px, 6vw, 68px);
  line-height: 1.05;
  letter-spacing: -0.02em;
}
.hero h1 em { font-style: normal; color: var(--cyan); }
.lede { margin: 20px 0 28px; max-width: 38em; font-size: 16px; }
.cta { display: flex; gap: 12px; flex-wrap: wrap; }
.btn {
  display: inline-flex;
  align-items: center;
  height: 48px;
  padding: 0 22px;
  border-radius: 100px;
  font-weight: 600;
  color: var(--bg);
  background: var(--cyan);
}
.btn.ghost {
  color: var(--text);
  background: transparent;
  border: 1px solid var(--border);
}

.radar {
  position: relative;
  aspect-ratio: 1;
  max-width: 420px;
  margin: 0 auto;
  border-radius: 50%;
  background: radial-gradient(circle at 50% 50%, var(--card-cyan), #0b0f14 68%);
  border: 1px solid var(--border);
  overflow: hidden;
}
.radar span.ring {
  position: absolute;
  inset: 12%;
  border: 1px solid rgba(34, 211, 238, 0.18);
  border-radius: 50%;
}
.radar span.ring:nth-child(2) { inset: 24%; }
.radar span.ring:nth-child(3) { inset: 36%; }
.radar .sweep {
  position: absolute;
  inset: 8%;
  background: conic-gradient(from 0deg, transparent 0 70%, rgba(34, 211, 238, 0.28) 88%, transparent 100%);
  animation: spin 6s linear infinite;
}
.radar .core {
  position: absolute;
  inset: 44%;
  border-radius: 50%;
  background: var(--amber);
  box-shadow: 0 0 24px var(--amber);
}
@keyframes spin { to { transform: rotate(1turn); } }

.grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
  margin: 24px 0 64px;
}
.card {
  padding: 22px;
  border-radius: 20px;
  background: var(--surface);
  border: 1px solid var(--border);
}
.card h3 { margin: 0 0 8px; color: var(--text); font-size: 18px; }
.card p { margin: 0; font-size: 14px; }
.card.wide { grid-column: 1 / -1; background: linear-gradient(120deg, #0e7490, #173f51 45%, var(--elevated)); }
.card.wide h3, .card.wide p { color: var(--text); }

.legal-links {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}
.legal-links a {
  padding: 10px 14px;
  border-radius: 100px;
  border: 1px solid var(--border);
  color: var(--secondary);
  font-size: 13px;
}
.legal-links a:hover { border-color: var(--cyan); color: var(--text); }

@media (max-width: 800px) {
  .hero, .grid { grid-template-columns: 1fr; }
  .bar { flex-direction: column; align-items: flex-start; }
  .card.wide { grid-column: auto; }
}