/* ===== 云枢在线 · 全局样式 ===== */
:root {
  --primary: #0ea5a4;
  --primary-dark: #0c8a89;
  --primary-light: #d7f3f2;
  --accent: #f59e0b;
  --ink: #1f2937;
  --ink-soft: #5b6675;
  --line: #e5e7eb;
  --bg: #f7faf9;
  --card: #ffffff;
  --shadow: 0 8px 24px rgba(15, 23, 42, .06);
  --radius: 14px;
  --maxw: 1180px;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}
a { color: inherit; text-decoration: none; }
img { max-width: 100%; display: block; }
.container { max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }

/* ===== 顶部导航 ===== */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: rgba(255,255,255,.92);
  backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--line);
}
.nav { display: flex; align-items: center; gap: 26px; height: 64px; }
.logo { display: flex; align-items: center; gap: 10px; font-weight: 800; font-size: 20px; color: var(--primary-dark); }
.logo .dot { width: 30px; height: 30px; border-radius: 9px; background: linear-gradient(135deg, var(--primary), #34d399); display: grid; place-items: center; color: #fff; font-size: 16px; }
.nav-links { display: flex; gap: 22px; margin-left: auto; }
.nav-links a { color: var(--ink-soft); font-weight: 500; font-size: 15px; padding: 6px 2px; border-bottom: 2px solid transparent; }
.nav-links a:hover, .nav-links a.active { color: var(--primary-dark); border-color: var(--primary); }
.nav-cta { display: flex; gap: 10px; align-items: center; }

/* ===== 按钮 ===== */
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; padding: 11px 20px; border-radius: 999px; font-weight: 600; font-size: 15px; cursor: pointer; border: 1px solid transparent; transition: .18s; }
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); transform: translateY(-1px); }
.btn-ghost { background: #fff; color: var(--primary-dark); border-color: var(--primary); }
.btn-ghost:hover { background: var(--primary-light); }
.btn-block { width: 100%; }

/* ===== Hero ===== */
.hero { padding: 70px 0 50px; background: radial-gradient(1200px 400px at 70% -10%, #d7f3f2 0%, transparent 60%), linear-gradient(180deg, #fff, var(--bg)); }
.hero h1 { font-size: 44px; line-height: 1.2; letter-spacing: -.5px; }
.hero h1 .hl { color: var(--primary); }
.hero p { margin: 18px 0 28px; font-size: 18px; color: var(--ink-soft); max-width: 640px; }
.hero-actions { display: flex; gap: 14px; flex-wrap: wrap; }
.hero-stats { display: flex; gap: 40px; margin-top: 42px; }
.hero-stats .num { font-size: 28px; font-weight: 800; color: var(--primary-dark); }
.hero-stats .lbl { font-size: 14px; color: var(--ink-soft); }

/* ===== 区块 ===== */
.section { padding: 60px 0; }
.section-head { text-align: center; margin-bottom: 38px; }
.section-head h2 { font-size: 30px; letter-spacing: -.3px; }
.section-head p { color: var(--ink-soft); margin-top: 8px; }

/* ===== 类目 ===== */
.cats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }
.cat-card { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 22px; text-align: center; transition: .18s; }
.cat-card:hover { transform: translateY(-3px); box-shadow: var(--shadow); border-color: var(--primary); }
.cat-emoji { font-size: 34px; }
.cat-card h3 { margin: 10px 0 4px; font-size: 17px; }
.cat-card p { font-size: 13px; color: var(--ink-soft); }

/* ===== 课程网格 ===== */
.grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px; }
.course { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; transition: .18s; display: flex; flex-direction: column; }
.course:hover { transform: translateY(-4px); box-shadow: var(--shadow); }
.cover { height: 150px; position: relative; display: grid; place-items: center; }
.cover .big { font-size: 52px; filter: drop-shadow(0 4px 8px rgba(0,0,0,.15)); }
.cover .badge { position: absolute; top: 12px; left: 12px; background: rgba(255,255,255,.92); color: var(--ink); font-size: 12px; font-weight: 600; padding: 4px 10px; border-radius: 999px; }
.course-body { padding: 16px 16px 18px; display: flex; flex-direction: column; gap: 8px; flex: 1; }
.course-body h3 { font-size: 16px; line-height: 1.4; }
.course-meta { display: flex; gap: 12px; font-size: 13px; color: var(--ink-soft); }
.course-foot { display: flex; align-items: center; justify-content: space-between; margin-top: auto; }
.price { font-weight: 800; color: var(--primary-dark); }
.price.free { color: #16a34a; }

/* ===== 优势 ===== */
.feats { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.feat { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 26px; }
.feat .ic { width: 46px; height: 46px; border-radius: 12px; background: var(--primary-light); color: var(--primary-dark); display: grid; place-items: center; font-size: 22px; margin-bottom: 14px; }
.feat h3 { font-size: 18px; margin-bottom: 6px; }
.feat p { color: var(--ink-soft); font-size: 14px; }

/* ===== 会员 CTA ===== */
.cta { background: linear-gradient(135deg, var(--primary), #0c8a89); color: #fff; border-radius: 20px; padding: 48px; text-align: center; }
.cta h2 { font-size: 28px; }
.cta p { opacity: .9; margin: 10px 0 22px; }

/* ===== 课程详情 ===== */
.detail-hero { padding: 40px 0; background: linear-gradient(180deg,#fff,var(--bg)); }
.detail-hero .cover { height: 200px; border-radius: var(--radius); margin-bottom: 22px; }
.detail-hero h1 { font-size: 32px; }
.detail-meta { display: flex; gap: 18px; flex-wrap: wrap; color: var(--ink-soft); margin: 14px 0; font-size: 15px; }
.detail-grid { display: grid; grid-template-columns: 1fr 320px; gap: 30px; align-items: start; }
.panel { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 24px; margin-bottom: 22px; }
.panel h3 { font-size: 19px; margin-bottom: 14px; }
.learn li { margin: 8px 0 8px 20px; }
.outline { list-style: none; }
.outline li { display: flex; gap: 12px; padding: 12px 0; border-bottom: 1px dashed var(--line); }
.outline .n { width: 26px; height: 26px; border-radius: 50%; background: var(--primary-light); color: var(--primary-dark); font-weight: 700; display: grid; place-items: center; font-size: 13px; flex: none; }
.teacher { display: flex; gap: 14px; align-items: center; }
.teacher .av { width: 52px; height: 52px; border-radius: 50%; background: linear-gradient(135deg,var(--primary),#34d399); color:#fff; display:grid; place-items:center; font-weight:700; font-size:18px; }
.buy-box { position: sticky; top: 84px; }
.buy-box .price-big { font-size: 30px; font-weight: 800; color: var(--primary-dark); }
.buy-box .row { display: flex; justify-content: space-between; padding: 10px 0; border-bottom: 1px solid var(--line); font-size: 14px; color: var(--ink-soft); }

/* ===== 表单 / 会员 ===== */
.auth-wrap { max-width: 440px; margin: 50px auto; }
.auth-card { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 32px; box-shadow: var(--shadow); }
.auth-card h2 { text-align: center; margin-bottom: 6px; }
.auth-card .sub { text-align: center; color: var(--ink-soft); font-size: 14px; margin-bottom: 22px; }
.field { margin-bottom: 16px; }
.field label { display: block; font-size: 14px; font-weight: 600; margin-bottom: 6px; }
.field input { width: 100%; padding: 12px 14px; border: 1px solid var(--line); border-radius: 10px; font-size: 15px; outline: none; transition:.15s; }
.field input:focus { border-color: var(--primary); box-shadow: 0 0 0 3px var(--primary-light); }
.switch-line { text-align: center; margin-top: 16px; font-size: 14px; color: var(--ink-soft); }
.switch-line a { color: var(--primary-dark); font-weight: 600; }
.alert { padding: 10px 14px; border-radius: 10px; font-size: 14px; margin-bottom: 14px; }
.alert-err { background: #fef2f2; color: #b91c1c; border: 1px solid #fecaca; }
.alert-ok { background: #ecfdf5; color: #047857; border: 1px solid #a7f3d0; }
.profile-head { display: flex; align-items: center; gap: 16px; margin-bottom: 18px; }
.profile-head .av { width: 60px; height: 60px; border-radius: 50%; background: linear-gradient(135deg,var(--primary),#34d399); color:#fff; display:grid; place-items:center; font-size:22px; font-weight:700; }
.tag { display:inline-block; background: var(--primary-light); color: var(--primary-dark); font-size:12px; padding:3px 10px; border-radius:999px; margin-right:6px; }

/* ===== 文章页 ===== */
.article { max-width: 820px; margin: 40px auto; background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 40px; }
.article h1 { font-size: 30px; margin-bottom: 8px; }
.article .date { color: var(--ink-soft); font-size: 14px; margin-bottom: 24px; }
.article h2 { font-size: 21px; margin: 26px 0 10px; }
.article p, .article li { color: #374151; margin: 8px 0; }
.article ul { margin-left: 22px; }

/* ===== 页脚 ===== */
.site-footer { background: #0f172a; color: #cbd5e1; padding: 46px 0 26px; margin-top: 40px; }
.footer-grid { display: grid; grid-template-columns: 1.6fr 1fr 1fr 1fr; gap: 30px; }
.site-footer h4 { color: #fff; font-size: 15px; margin-bottom: 14px; }
.site-footer a { color: #cbd5e1; font-size: 14px; display: block; padding: 4px 0; }
.site-footer a:hover { color: #fff; }
.footer-about p { font-size: 14px; line-height: 1.7; }
.footer-bottom { border-top: 1px solid #1e293b; margin-top: 30px; padding-top: 18px; text-align: center; font-size: 13px; color: #94a3b8; }
.footer-bottom a { color: #94a3b8; display: inline; }

/* ===== 响应式 ===== */
@media (max-width: 920px) {
  .cats, .grid, .feats { grid-template-columns: repeat(2, 1fr); }
  .detail-grid { grid-template-columns: 1fr; }
  .buy-box { position: static; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .hero h1 { font-size: 34px; }
}
@media (max-width: 600px) {
  .nav-links { display: none; }
  .cats, .grid, .feats { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; }
  .hero-stats { gap: 24px; }
  .cta { padding: 32px 20px; }
  .hero h1 { font-size: 28px; }
}