:root {
  --bg: #07070F;
  --hero-1: #0A0A1A;
  --hero-2: #1A1A3A;
  --accent: #4A9EFF;
  --text: #E8ECF5;
  --muted: #9AA4BF;
  --card: #101024;
  --border: rgba(255, 255, 255, 0.08);
  --radius: 16px;
  --maxw: 1080px;
}
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  font-size: 16px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}
a { color: inherit; text-decoration: none; }
/* ---------- 导航 ---------- */
.nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
  transition: background-color .3s ease, backdrop-filter .3s ease, border-color .3s ease;
  border-bottom: 1px solid transparent;
}
.nav.is-scrolled {
  background: rgba(7, 7, 15, 0.82);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom-color: var(--border);
}
.nav-brand { font-size: 16px; font-weight: 600; letter-spacing: 2px; }
.nav-links { display: flex; gap: 22px; font-size: 14px; color: var(--muted); }
.nav-links a { transition: color .2s ease; }
.nav-links a:hover { color: var(--accent); }
/* ---------- 首屏 ---------- */
.hero {
  position: relative;
  min-height: 100vh;
  min-height: 100svh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 96px 24px 80px;
  background: linear-gradient(160deg, var(--hero-1) 0%, var(--hero-2) 100%);
  overflow: hidden;
}
.hero::after {
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(circle at 50% 42%, rgba(74, 158, 255, 0.18), transparent 62%);
  pointer-events: none;
}
.hero-inner { position: relative; z-index: 1; max-width: 680px; }
.brand {
  font-size: clamp(40px, 9vw, 68px);
  font-weight: 700;
  letter-spacing: 10px;
  text-indent: 10px;
  margin-bottom: 20px;
}
.slogan {
  font-size: clamp(18px, 3.6vw, 24px);
  letter-spacing: 4px;
  text-indent: 4px;
  color: var(--accent);
  margin-bottom: 18px;
}
.hero-sub { font-size: 15px; color: var(--muted); letter-spacing: .5px; }
.scroll-hint {
  position: absolute;
  bottom: 36px;
  left: 50%;
  transform: translateX(-50%);
  width: 24px; height: 38px;
  border: 1px solid rgba(255, 255, 255, 0.25);
  border-radius: 14px;
  z-index: 1;
}
.scroll-hint span {
  position: absolute;
  top: 8px; left: 50%;
  width: 3px; height: 7px;
  margin-left: -1.5px;
  border-radius: 2px;
  background: var(--accent);
  animation: hint 1.8s ease-in-out infinite;
}
@keyframes hint {
  0%, 100% { transform: translateY(0); opacity: 1; }
  50% { transform: translateY(12px); opacity: .25; }
}
/* ---------- 区块 ---------- */
.section {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 88px 24px;
}
.section-title {
  font-size: 24px;
  font-weight: 600;
  letter-spacing: 3px;
  text-align: center;
  margin-bottom: 12px;
}
.section-desc {
  text-align: center;
  color: var(--muted);
  font-size: 14px;
  margin-bottom: 48px;
}
/* ---------- 卡片 ---------- */
.cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 22px;
}
.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px 26px 28px;
  transition: transform .3s ease, border-color .3s ease;
}
.card:hover { transform: translateY(-4px); border-color: rgba(74, 158, 255, 0.4); }
.card-title { font-size: 18px; font-weight: 600; letter-spacing: 1px; margin-bottom: 10px; }
.card-text { font-size: 14px; color: var(--muted); min-height: 48px; }
/* 卡片图标 */
.card-icon { position: relative; width: 52px; height: 52px; margin-bottom: 20px; }
.card-icon::before,
.card-icon::after { content: ""; position: absolute; }
.icon-box::before {
  inset: 8px;
  border: 2px solid var(--accent);
  border-radius: 6px;
  transform: rotate(45deg);
}
.icon-box::after {
  inset: 17px;
  border: 2px solid var(--accent);
  border-radius: 4px;
  transform: rotate(45deg);
  opacity: .45;
}
.icon-book::before {
  inset: 6px 12px;
  border: 2px solid var(--accent);
  border-radius: 4px;
}
.icon-book::after {
  top: 6px; bottom: 6px; left: 50%;
  width: 2px;
  margin-left: -1px;
  background: var(--accent);
  opacity: .45;
}
.icon-frame::before {
  inset: 6px;
  border: 2px solid var(--accent);
  border-radius: 4px;
}
.icon-frame::after {
  inset: 18px;
  border: 2px dashed var(--accent);
  border-radius: 2px;
  opacity: .55;
}
/* 卡片预览 */
.card-preview {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 20px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
}
.tag {
  font-size: 12px;
  color: var(--muted);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 3px 12px;
}
.line {
  height: 8px;
  width: 100%;
  border-radius: 4px;
  background: rgba(255, 255, 255, 0.06);
  margin-bottom: 10px;
}
.line.short { width: 62%; }
.thumb {
  width: 46px; height: 46px;
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.06);
}
.cards-note {
  text-align: center;
  color: var(--muted);
  font-size: 14px;
  letter-spacing: 1px;
  margin-top: 44px;
}
/* ---------- 页脚 ---------- */
.footer {
  border-top: 1px solid var(--border);
  padding: 40px 24px 48px;
  text-align: center;
}
.footer-brand { font-size: 14px; color: var(--muted); letter-spacing: .5px; margin-bottom: 8px; }
.footer-copy { font-size: 13px; color: rgba(154, 164, 191, 0.6); }
/* ---------- 滚动淡入 ---------- */
.reveal {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity .6s ease, transform .6s ease;
}
.reveal.is-in { opacity: 1; transform: translateY(0); }
/* ---------- 响应式 ---------- */
@media (max-width: 860px) {
  .cards { grid-template-columns: 1fr; }
  .card-text { min-height: 0; }
}
@media (max-width: 640px) {
  .nav { padding: 12px 18px; }
  .nav-links { gap: 16px; font-size: 13px; }
  .brand { letter-spacing: 6px; text-indent: 6px; }
  .section { padding: 64px 18px; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .reveal { opacity: 1; transform: none; transition: none; }
  .scroll-hint span { animation: none; }
}