/* ===== 司南 AI 教学助手 官网样式 ===== */
:root {
  --blue-900: #16335F;
  --blue-700: #1F4E9C;
  --blue-500: #2E6BC4;
  --blue-100: #E8F0FB;
  --orange-500: #E85D2A;
  --ink: #1F2937;
  --ink-light: #6B7280;
  --bg-warm: #FAF8F5;
  --border: #E5E7EB;
  --white: #FFFFFF;
  --radius: 10px;
  --shadow: 0 4px 16px rgba(31, 78, 156, 0.08);
  --shadow-hover: 0 10px 28px rgba(31, 78, 156, 0.16);
  --maxw: 1120px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", sans-serif;
  color: var(--ink);
  background: var(--white);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--blue-500); text-decoration: none; }
a:hover { text-decoration: underline; }

.container { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }

/* ===== 导航栏 ===== */
.nav {
  position: sticky; top: 0; z-index: 100;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.nav-inner {
  max-width: var(--maxw); margin: 0 auto; padding: 0 24px;
  height: 64px; display: flex; align-items: center; justify-content: space-between;
}
.nav-logo { display: flex; align-items: center; gap: 10px; font-weight: 600; color: var(--ink); font-size: 17px; }
.nav-logo img { height: 30px; width: auto; }
.nav-links { display: flex; align-items: center; gap: 28px; font-size: 15px; }
.nav-links a { color: var(--ink-light); transition: color 0.15s; }
.nav-links a:hover { color: var(--blue-700); text-decoration: none; }
.nav-cta {
  background: var(--blue-700); color: #fff !important;
  padding: 8px 18px; border-radius: 8px; font-size: 14px;
  transition: background 0.15s;
}
.nav-cta:hover { background: var(--blue-900); text-decoration: none; }

/* ===== Hero ===== */
.hero {
  background: linear-gradient(160deg, #16335F 0%, #1F4E9C 55%, #2E6BC4 100%);
  color: #fff; padding: 96px 0 84px; overflow: hidden;
}
.hero-grid {
  max-width: var(--maxw); margin: 0 auto; padding: 0 24px;
  display: grid; grid-template-columns: 1.15fr 0.85fr; gap: 56px; align-items: center;
}
.hero-badge {
  display: inline-block; background: rgba(255,255,255,0.14); border: 1px solid rgba(255,255,255,0.25);
  padding: 5px 14px; border-radius: 999px; font-size: 13px; margin-bottom: 22px; letter-spacing: 0.5px;
}
.hero h1 { font-size: 42px; line-height: 1.3; font-weight: 700; margin-bottom: 20px; letter-spacing: 0.5px; }
.hero p.lead { font-size: 17px; color: rgba(255,255,255,0.85); max-width: 540px; margin-bottom: 36px; }
.hero-ctas { display: flex; gap: 14px; flex-wrap: wrap; }
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 13px 28px; border-radius: 10px; font-size: 15px; font-weight: 600;
  transition: transform 0.15s, box-shadow 0.15s, background 0.15s;
  cursor: pointer; border: none;
}
.btn-primary { background: #fff; color: var(--blue-900); }
.btn-primary:hover { background: var(--blue-100); transform: translateY(-2px); box-shadow: 0 8px 20px rgba(0,0,0,0.18); text-decoration: none; }
.btn-ghost { background: rgba(255,255,255,0.12); color: #fff; border: 1px solid rgba(255,255,255,0.35); }
.btn-ghost:hover { background: rgba(255,255,255,0.2); transform: translateY(-2px); text-decoration: none; }
.hero-visual {
  background: rgba(255,255,255,0.06); border: 1px solid rgba(255,255,255,0.14);
  border-radius: 16px; padding: 28px; backdrop-filter: blur(6px);
}
.hero-visual img { width: 100%; height: auto; display: block; border-radius: 8px; }
.hero-stats { display: flex; gap: 36px; margin-top: 44px; }
.hero-stat b { font-size: 26px; display: block; font-weight: 700; }
.hero-stat span { font-size: 13px; color: rgba(255,255,255,0.75); }

/* ===== 功能 ===== */
.section { padding: 88px 0; }
.section-alt { background: var(--bg-warm); }
.section-head { text-align: center; max-width: 640px; margin: 0 auto 56px; }
.section-head h2 { font-size: 30px; font-weight: 700; color: var(--blue-900); margin-bottom: 14px; }
.section-head p { color: var(--ink-light); font-size: 16px; }

.cards { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.card {
  background: var(--white); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 32px 28px; transition: transform 0.18s, box-shadow 0.18s;
}
.card:hover { transform: translateY(-4px); box-shadow: var(--shadow-hover); }
.card-icon {
  width: 48px; height: 48px; border-radius: 12px; display: flex; align-items: center; justify-content: center;
  font-size: 24px; margin-bottom: 18px;
}
.card-icon.b1 { background: var(--blue-100); }
.card-icon.b2 { background: #FDEBE3; }
.card-icon.b3 { background: #E8F6EF; }
.card h3 { font-size: 18px; margin-bottom: 10px; color: var(--blue-900); }
.card p { font-size: 14.5px; color: var(--ink-light); }

/* ===== 下载 ===== */
.download-box {
  max-width: 760px; margin: 0 auto; background: var(--white);
  border: 1px solid var(--border); border-radius: 14px; padding: 44px;
  box-shadow: var(--shadow);
}
.dl-platform { display: flex; justify-content: space-between; align-items: center; padding: 22px 0; border-bottom: 1px solid var(--border); }
.dl-platform:last-child { border-bottom: none; }
.dl-name { font-size: 16px; font-weight: 600; display: flex; align-items: center; gap: 10px; }
.dl-name .os { width: 36px; height: 36px; border-radius: 8px; display: inline-flex; align-items: center; justify-content: center; font-size: 18px; background: var(--blue-100); }
.dl-desc { font-size: 13px; color: var(--ink-light); margin-top: 2px; }
.btn-download { background: var(--blue-700); color: #fff; padding: 10px 22px; border-radius: 8px; font-size: 14px; font-weight: 600; }
.btn-download:hover { background: var(--blue-900); text-decoration: none; transform: translateY(-1px); }
.btn-disabled { background: #D1D5DB; color: #fff; cursor: not-allowed; pointer-events: none; }
.dl-note { text-align: center; font-size: 13px; color: var(--ink-light); margin-top: 24px; }

/* ===== 页脚 ===== */
.footer { background: var(--blue-900); color: rgba(255,255,255,0.8); padding: 48px 0 40px; font-size: 14px; }
.footer-inner { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }
.footer-top { display: flex; justify-content: space-between; align-items: flex-start; gap: 32px; flex-wrap: wrap; margin-bottom: 32px; }
.footer-brand img { height: 28px; width: auto; margin-bottom: 10px; }
.footer-links { display: flex; gap: 24px; }
.footer-links a { color: rgba(255,255,255,0.75); }
.footer-links a:hover { color: #fff; }
.footer-icp { border-top: 1px solid rgba(255,255,255,0.15); padding-top: 24px; text-align: center; color: rgba(255,255,255,0.6); font-size: 13px; }
.footer-icp a { color: rgba(255,255,255,0.75); }

/* ===== 文本页(隐私/协议) ===== */
.page { max-width: 800px; margin: 0 auto; padding: 56px 24px 88px; }
.page h1 { font-size: 30px; color: var(--blue-900); margin-bottom: 8px; }
.page .updated { font-size: 13px; color: var(--ink-light); margin-bottom: 36px; }
.page h2 { font-size: 19px; color: var(--blue-900); margin: 32px 0 12px; }
.page p, .page li { font-size: 15px; color: #374151; margin-bottom: 10px; }
.page ul, .page ol { padding-left: 24px; margin-bottom: 10px; }

/* ===== 响应式 ===== */
@media (max-width: 860px) {
  .hero { padding: 64px 0 56px; }
  .hero-grid { grid-template-columns: 1fr; gap: 36px; }
  .hero h1 { font-size: 32px; }
  .cards { grid-template-columns: 1fr; }
  .nav-links { display: none; }
  .hero-stats { flex-wrap: wrap; gap: 24px; }
}