/* ============================================================
   Dancesea Group · 跳动海外集团官网 · Linear Dark v3 风格
   ============================================================
   复刻 os.dancesea.com (intranet) 同款颜色 / 字体 / 间距
   SAM 2026-05-21 拍板:急办公司官网过 TT API 审核
   ============================================================ */

:root {
  --bg-0:        #08090A;
  --bg-1:        #0E0F11;
  --bg-2:        #131517;
  --bg-3:        #1A1D1F;
  --bg-4:        #232628;
  --border-soft: rgba(255, 255, 255, 0.06);
  --border-mid:  rgba(255, 255, 255, 0.10);
  --border-hard: rgba(255, 255, 255, 0.14);
  --text-0:  #F7F8F8;
  --text-1:  #D0D6DB;
  --text-2:  #8A8F98;
  --text-3:  #62666D;
  --accent:        #7B7FE8;
  --accent-hover:  #9094EC;
  --accent-soft:   rgba(123, 127, 232, 0.12);
  --accent-border: rgba(123, 127, 232, 0.32);
  --brand-crftop:    #5B9BD5;
  --brand-keepreety: #8FB89F;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
  background: var(--bg-0);
  color: var(--text-0);
  font-family: -apple-system, BlinkMacSystemFont, "Inter", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Segoe UI", sans-serif;
  font-size: 16px;
  line-height: 1.6;
  letter-spacing: -0.005em;
  font-feature-settings: "tnum" 1;
  -webkit-font-smoothing: antialiased;
}

/* ===== Navbar ===== */
.nav {
  position: sticky; top: 0; z-index: 100;
  background: rgba(8,9,10,0.85);
  backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border-soft);
}
.nav-inner {
  max-width: 1200px; margin: 0 auto; padding: 16px 32px;
  display: flex; justify-content: space-between; align-items: center;
}
.logo { font-size: 18px; font-weight: 600; letter-spacing: -0.02em; color: var(--text-0); text-decoration: none; }
.logo span { color: var(--accent); }
.nav-links { display: flex; gap: 32px; align-items: center; }
.nav-links a { color: var(--text-2); text-decoration: none; font-size: 14px; transition: color 160ms; }
.nav-links a:hover { color: var(--text-0); }

/* ===== Language Toggle EN | 中 ===== */
.lang-toggle {
  display: inline-flex; align-items: center;
  height: 28px; padding: 2px; border-radius: 999px;
  background: var(--bg-2); border: 1px solid var(--border-soft);
  margin-left: 8px;
}
.lang-toggle button {
  height: 24px; padding: 0 10px; border-radius: 999px;
  background: transparent; border: none;
  color: var(--text-3); font-size: 12px; font-weight: 500;
  cursor: pointer; transition: all 160ms;
  font-family: inherit;
}
.lang-toggle button:hover { color: var(--text-1); }
.lang-toggle button.active {
  background: var(--accent); color: white;
}

/* ===== Hero ===== */
.hero {
  position: relative; overflow: hidden;
  padding: 96px 32px 64px; text-align: center;
  max-width: 1400px; margin: 0 auto;
}
.hero-venn { position: relative; max-width: 1000px; margin: 0 auto 48px; }

.tag {
  display: inline-flex; align-items: center; gap: 8px;
  height: 28px; padding: 0 12px; border-radius: 999px;
  background: var(--bg-2); border: 1px solid var(--border-soft);
  color: var(--text-1); font-size: 12px; margin-bottom: 32px;
}
.tag-dot { width: 6px; height: 6px; border-radius: 50%; background: var(--accent); }

.entities {
  font-family: "JetBrains Mono", "SF Mono", ui-monospace, monospace;
  font-size: 12px; color: var(--text-3);
  text-transform: uppercase; letter-spacing: 0.15em;
  margin-bottom: 24px;
}

.h1 {
  font-size: clamp(40px, 6vw, 80px); font-weight: 600;
  line-height: 1.05; letter-spacing: -0.04em;
  max-width: 900px; margin: 0 auto 24px;
  background: linear-gradient(180deg, #F7F8F8 0%, #A8AEB5 100%);
  -webkit-background-clip: text; background-clip: text;
  -webkit-text-fill-color: transparent;
}
.hero-sub {
  font-size: clamp(16px, 1.6vw, 20px); color: var(--text-2);
  max-width: 640px; margin: 0 auto 40px; line-height: 1.5;
}
.cta-row { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  height: 44px; padding: 0 20px; border-radius: 8px;
  font-size: 14px; font-weight: 500; text-decoration: none;
  transition: all 160ms cubic-bezier(0.22, 1, 0.36, 1);
  cursor: pointer; border: 1px solid transparent;
}
.btn-primary { background: var(--accent); color: white; }
.btn-primary:hover { background: var(--accent-hover); transform: translateY(-1px); }
.btn-ghost { background: var(--bg-2); color: var(--text-0); border-color: var(--border-mid); }
.btn-ghost:hover { background: var(--bg-3); border-color: var(--border-hard); }

/* ===== Sections ===== */
.section {
  max-width: 1200px; margin: 0 auto;
  padding: 96px 32px;
}
.section-tag {
  font-family: "JetBrains Mono", "SF Mono", ui-monospace, monospace;
  font-size: 11px; color: var(--accent);
  text-transform: uppercase; letter-spacing: 0.2em; margin-bottom: 16px;
}
.section-title {
  font-size: clamp(28px, 4vw, 48px); font-weight: 600;
  letter-spacing: -0.03em; line-height: 1.1;
  color: var(--text-0); margin-bottom: 24px; max-width: 720px;
}
.section-sub {
  font-size: 18px; color: var(--text-2); line-height: 1.6;
  max-width: 720px; margin-bottom: 64px;
}

/* ===== Brand Matrix ===== */
.brands-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 24px; }
.brand-card {
  background: var(--bg-1); border: 1px solid var(--border-soft);
  border-radius: 16px; padding: 32px;
  transition: all 320ms cubic-bezier(0.22, 1, 0.36, 1);
}
.brand-card:hover { background: var(--bg-2); border-color: var(--border-mid); transform: translateY(-2px); }
.brand-card.featured { grid-column: span 1; }
.brand-card .badge {
  display: inline-block; padding: 4px 10px; border-radius: 6px;
  font-size: 11px; font-family: "JetBrains Mono", "SF Mono", monospace;
  text-transform: uppercase; letter-spacing: 0.1em; margin-bottom: 16px;
}
.badge-owned { background: rgba(91,155,213,0.12); color: var(--brand-crftop); }
.badge-sub { background: rgba(143,184,159,0.12); color: var(--brand-keepreety); }
.badge-agency { background: rgba(123,127,232,0.12); color: var(--accent); }
.badge-partner { background: rgba(255,255,255,0.06); color: var(--text-2); }

.brand-card h3 { font-size: 26px; font-weight: 600; letter-spacing: -0.02em; margin-bottom: 8px; color: var(--text-0); }
.brand-card p.tagline { font-size: 14px; color: var(--text-2); margin-bottom: 16px; }
.brand-card p.desc { font-size: 14px; color: var(--text-1); line-height: 1.6; }

/* ===== Stats Row ===== */
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 24px; margin-top: 48px; }
.stat {
  background: var(--bg-1); border: 1px solid var(--border-soft);
  border-radius: 12px; padding: 24px;
}
.stat-num {
  font-size: 36px; font-weight: 600; letter-spacing: -0.03em;
  color: var(--text-0); font-feature-settings: "tnum" 1;
  margin-bottom: 4px;
}
.stat-label { font-size: 13px; color: var(--text-2); }

/* ===== Footer ===== */
.footer {
  border-top: 1px solid var(--border-soft);
  padding: 48px 32px 32px; margin-top: 64px;
}
.footer-inner {
  max-width: 1200px; margin: 0 auto;
  display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 48px;
}
.footer h4 { font-size: 12px; color: var(--text-2); text-transform: uppercase; letter-spacing: 0.15em; margin-bottom: 16px; font-weight: 500; }
.footer ul { list-style: none; }
.footer li { margin-bottom: 8px; }
.footer a, .footer p { color: var(--text-1); text-decoration: none; font-size: 14px; transition: color 160ms; }
.footer a:hover { color: var(--text-0); }
.footer-bottom {
  max-width: 1200px; margin: 32px auto 0;
  padding-top: 24px; border-top: 1px solid var(--border-soft);
  display: flex; justify-content: space-between; flex-wrap: wrap; gap: 16px;
  color: var(--text-3); font-size: 12px;
}

/* ===== Prose (about / privacy) ===== */
.prose {
  max-width: 720px; margin: 0 auto;
  color: var(--text-1);
}
.prose h2 { font-size: 28px; font-weight: 600; letter-spacing: -0.025em; margin: 48px 0 16px; color: var(--text-0); }
.prose h3 { font-size: 20px; font-weight: 600; margin: 32px 0 12px; color: var(--text-0); }
.prose p { margin-bottom: 16px; font-size: 16px; line-height: 1.7; }
.prose ul, .prose ol { margin: 16px 0 16px 24px; }
.prose li { margin-bottom: 8px; }
.prose strong { color: var(--text-0); font-weight: 600; }
.prose a { color: var(--accent); text-decoration: underline; text-decoration-color: var(--accent-border); }
.prose a:hover { color: var(--accent-hover); }

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .nav-links { gap: 16px; }
  .brands-grid { grid-template-columns: 1fr; }
  .stats { grid-template-columns: repeat(2, 1fr); }
  .footer-inner { grid-template-columns: 1fr 1fr; gap: 32px; }
  .section { padding: 64px 24px; }
  .hero { padding: 64px 24px 48px; }
}

/* ===== Venn animation ===== */
@keyframes hero-venn-orbit {
  from { stroke-dashoffset: 0; }
  to   { stroke-dashoffset: -100; }
}
.hero-venn-arc { animation: hero-venn-orbit 22s linear infinite; will-change: stroke-dashoffset; }
.hero-venn-arc-left  { stroke-dashoffset: -25; }
.hero-venn-arc-right { animation-delay: -11s; }