/* =====================================================
   ZetaSphere — design system: dark, tech, purple↔magenta
   ===================================================== */

:root{
  color-scheme: dark;
  --bg-void:#050308;
  --bg-1:#0a0512;
  --bg-2:#100819;
  --surface: rgba(255,255,255,.035);
  --surface-hover: rgba(255,255,255,.06);
  --border: rgba(255,255,255,.09);
  --border-strong: rgba(255,255,255,.18);

  --purple-700:#6d28d9;
  --purple-500:#8b5cf6;
  --purple-400:#a78bfa;
  --magenta-600:#c026d3;
  --magenta-500:#d946ef;
  --magenta-400:#e879f9;

  --grad-brand: linear-gradient(135deg,#8b5cf6 0%,#c026d3 55%,#e879f9 100%);
  --grad-brand-soft: linear-gradient(135deg, rgba(139,92,246,.16), rgba(217,70,239,.12));

  --text-1:#f6f3fa;
  --text-2:#beb2cc;
  --text-3:#8477974d;
  --text-muted:#8a7d99;

  --radius-sm: 10px;
  --radius-md: 16px;
  --radius-lg: 24px;

  --ff-display: 'Space Grotesk', 'Noto Sans SC', sans-serif;
  --ff-body: 'Inter', 'Noto Sans SC', sans-serif;
}

*,*::before,*::after{ box-sizing:border-box; }
html{ scroll-behavior:smooth; }
html[data-lang="zh"] body{ font-feature-settings:"palt"; }

body{
  margin:0;
  background:var(--bg-void);
  color:var(--text-1);
  font-family:var(--ff-body);
  font-size:16px;
  line-height:1.6;
  -webkit-font-smoothing:antialiased;
  overflow-x:hidden;
}

h1,h2,h3,h4{ font-family:var(--ff-display); font-weight:600; line-height:1.15; margin:0; letter-spacing:-0.01em; }
p{ margin:0; }
a{ color:inherit; text-decoration:none; }
ul{ margin:0; padding:0; list-style:none; }
button{ font-family:inherit; cursor:pointer; }

.wrap{ max-width:1180px; margin:0 auto; padding:0 28px; }

/* ---------- background fx ---------- */
.bg-fx{ position:fixed; inset:0; z-index:0; pointer-events:none; overflow:hidden; }
.bg-glow{ position:absolute; border-radius:50%; filter:blur(90px); opacity:.5; }
.bg-glow--1{ width:640px; height:640px; top:-220px; left:-160px; background:radial-gradient(circle, rgba(139,92,246,.35), transparent 70%); }
.bg-glow--2{ width:720px; height:720px; bottom:-260px; right:-200px; background:radial-gradient(circle, rgba(217,70,239,.28), transparent 70%); }
.bg-grid{
  position:absolute; inset:0;
  background-image:
    linear-gradient(rgba(255,255,255,.028) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,.028) 1px, transparent 1px);
  background-size:56px 56px;
  mask-image: radial-gradient(ellipse 80% 60% at 50% 0%, black 40%, transparent 90%);
}

main, header, footer, .modal{ position:relative; z-index:1; }

/* ---------- buttons ---------- */
.btn{
  display:inline-flex; align-items:center; justify-content:center; gap:8px;
  padding:13px 26px; border-radius:999px; border:1px solid transparent;
  font-family:var(--ff-display); font-weight:600; font-size:.94rem;
  transition:transform .18s ease, box-shadow .18s ease, border-color .18s ease, background .18s ease;
  white-space:nowrap;
}
.btn-primary{ background:var(--grad-brand); color:#0a0512; box-shadow:0 8px 30px -8px rgba(217,70,239,.55); }
.btn-primary:hover{ transform:translateY(-2px); box-shadow:0 14px 34px -8px rgba(217,70,239,.65); }
.btn-ghost{ background:rgba(255,255,255,.03); border-color:var(--border); color:var(--text-1); }
.btn-ghost:hover{ border-color:var(--border-strong); background:rgba(255,255,255,.06); }
.btn-lg{ padding:16px 34px; font-size:1rem; }

/* ---------- header ---------- */
.site-header{
  position:fixed; top:0; left:0; right:0; z-index:50;
  border-bottom:1px solid transparent;
  transition:background .25s ease, border-color .25s ease, backdrop-filter .25s ease;
}
.site-header.scrolled{
  background:rgba(6,3,12,.72);
  backdrop-filter:blur(14px) saturate(140%);
  border-bottom-color:var(--border);
}
.header-inner{ display:flex; align-items:center; justify-content:space-between; height:76px; gap:24px; }

.brand{ display:flex; align-items:center; gap:10px; flex-shrink:0; }
.brand-mark{ width:34px; height:34px; display:block; }
.brand-mark svg{ width:100%; height:100%; }
.brand-text{ display:flex; flex-direction:column; line-height:1.05; }
.brand-name{ font-family:var(--ff-display); font-weight:700; font-size:1.05rem; letter-spacing:.02em; }
.brand-sub{ font-size:.62rem; color:var(--text-muted); letter-spacing:.12em; }

.main-nav{ display:flex; align-items:center; gap:30px; margin-left:auto; }
.main-nav a{ font-size:.92rem; color:var(--text-2); transition:color .15s ease; }
.main-nav a:hover{ color:var(--text-1); }
.main-nav a.nav-cta{
  color:var(--text-1); border:1px solid var(--border-strong); padding:9px 18px; border-radius:999px;
  background:rgba(255,255,255,.03);
}
.main-nav a.nav-cta:hover{ background:rgba(255,255,255,.08); }

.header-actions{ display:flex; align-items:center; gap:14px; }
.lang-toggle{
  display:flex; align-items:center; gap:5px; background:rgba(255,255,255,.04);
  border:1px solid var(--border); border-radius:999px; padding:6px 12px; color:var(--text-2);
  font-family:var(--ff-display); font-size:.8rem; font-weight:600;
}
.lang-op{ opacity:.5; transition:opacity .15s ease; padding:0 1px;}
.lang-op.active{ opacity:1; color:var(--magenta-400); }
.lang-sep{ opacity:.3; }

.burger{ display:none; flex-direction:column; gap:5px; background:none; border:none; padding:6px; }
.burger span{ width:20px; height:2px; background:var(--text-1); border-radius:2px; }

/* ---------- hero ---------- */
.hero{ position:relative; min-height:100svh; display:flex; align-items:center; padding-top:76px; overflow:hidden; }
.hero-canvas{ position:absolute; inset:0; width:100%; height:100%; }
.hero-inner{ position:relative; z-index:2; max-width:760px; padding-top:20px; padding-bottom:60px; }

.eyebrow{
  display:inline-block; font-family:var(--ff-display); font-size:.8rem; font-weight:600;
  letter-spacing:.08em; text-transform:uppercase; color:var(--magenta-400);
  padding:6px 14px; border:1px solid rgba(217,70,239,.35); border-radius:999px;
  background:rgba(217,70,239,.08); margin-bottom:22px;
}
.hero-title{ font-size:clamp(2.4rem, 5.6vw, 4.1rem); margin-bottom:22px; }
.grad-text{
  background:var(--grad-brand); -webkit-background-clip:text; background-clip:text; color:transparent;
}
.hero-sub{ font-size:1.1rem; color:var(--text-2); max-width:600px; margin-bottom:34px; }
.hero-actions{ display:flex; gap:14px; flex-wrap:wrap; }

.hero-scroll-cue{ position:absolute; bottom:28px; left:50%; transform:translateX(-50%); z-index:2; }
.hero-scroll-cue span{
  display:block; width:22px; height:36px; border:1.5px solid var(--border-strong); border-radius:20px; position:relative;
}
.hero-scroll-cue span::before{
  content:""; position:absolute; top:6px; left:50%; transform:translateX(-50%);
  width:4px; height:8px; background:var(--magenta-400); border-radius:2px;
  animation:scrollcue 1.8s ease infinite;
}
@keyframes scrollcue{ 0%{ opacity:1; transform:translate(-50%,0);} 70%{opacity:0; transform:translate(-50%,10px);} 100%{opacity:0;} }

/* ---------- reveal ---------- */
.reveal{ opacity:0; transform:translateY(18px); transition:opacity .7s ease, transform .7s ease; }
.reveal.in{ opacity:1; transform:none; }
.reveal:nth-child(2){ transition-delay:.06s; }
.reveal:nth-child(3){ transition-delay:.12s; }
.reveal:nth-child(4){ transition-delay:.18s; }

/* ---------- partners ---------- */
.partners{ padding:36px 0; border-top:1px solid var(--border); border-bottom:1px solid var(--border); }
.partners-label{ font-size:.78rem; letter-spacing:.1em; text-transform:uppercase; color:var(--text-muted); margin-bottom:18px; }
.partners-row{ display:flex; flex-wrap:wrap; gap:14px; align-items:center; }
.partner-chip{
  display:flex; align-items:center; gap:9px; padding:10px 18px; border:1px solid var(--border);
  border-radius:999px; color:var(--text-2); font-family:var(--ff-display); font-weight:600; font-size:.92rem;
  background:var(--surface);
}
.partner-chip svg{ color:var(--purple-400); }
.partner-chip--muted{ color:var(--text-muted); font-weight:500; font-size:.82rem; border-style:dashed; }

/* ---------- stats ---------- */
.stats{ padding:64px 0; }
.stats-grid{ display:grid; grid-template-columns:repeat(4,1fr); gap:28px; }
.stat-num{ font-family:var(--ff-display); font-size:2.6rem; font-weight:700; background:var(--grad-brand); -webkit-background-clip:text; background-clip:text; color:transparent; display:flex; align-items:baseline; }
.stat-suffix{ font-size:1.6rem; margin-left:2px; }
.stat-label{ color:var(--text-2); font-size:.92rem; margin-top:6px; max-width:220px; }

/* ---------- sections ---------- */
.section{ padding:100px 0; }
.section--alt{ background:linear-gradient(180deg, transparent, rgba(139,92,246,.04) 20%, rgba(217,70,239,.04) 80%, transparent); }
.section-eyebrow{
  font-family:var(--ff-display); font-size:.8rem; font-weight:600; letter-spacing:.1em; text-transform:uppercase;
  color:var(--purple-400); margin-bottom:14px;
}
.section-title{ font-size:clamp(1.9rem, 3.4vw, 2.6rem); max-width:680px; margin-bottom:16px; }
.section-sub{ color:var(--text-2); max-width:640px; font-size:1.04rem; margin-bottom:52px; }

/* ---------- zetastack ---------- */
.zetastack{ display:grid; grid-template-columns:340px 1fr; gap:0; border:1px solid var(--border); border-radius:var(--radius-lg); overflow:hidden; background:var(--surface); }
.zetastack-layers{ border-right:1px solid var(--border); }
.stack-layer{
  display:flex; align-items:center; gap:16px; padding:22px 26px; border-bottom:1px solid var(--border);
  cursor:pointer; transition:background .18s ease; position:relative;
}
.stack-layer:last-child{ border-bottom:none; }
.stack-layer:hover{ background:rgba(255,255,255,.03); }
.stack-layer.active{ background:var(--grad-brand-soft); }
.stack-layer.active::before{ content:""; position:absolute; left:0; top:0; bottom:0; width:3px; background:var(--grad-brand); }
.stack-layer-no{ font-family:var(--ff-display); font-size:.78rem; color:var(--text-muted); width:22px; flex-shrink:0; }
.stack-layer.active .stack-layer-no{ color:var(--magenta-400); }
.stack-layer-name{ font-family:var(--ff-display); font-weight:600; font-size:1rem; }
.stack-layer-tag{ font-size:.78rem; color:var(--text-muted); margin-top:2px; }

.zetastack-detail{ padding:44px; display:flex; flex-direction:column; justify-content:center; }
.zetastack-detail h3{ font-size:1.5rem; margin-bottom:14px; }
.zetastack-detail p{ color:var(--text-2); font-size:1.02rem; margin-bottom:22px; max-width:520px; }
.zetastack-detail .sd-tags{ display:flex; flex-wrap:wrap; gap:9px; }
.zetastack-detail .sd-tags span{
  font-size:.8rem; padding:7px 14px; border-radius:999px; border:1px solid var(--border); color:var(--text-2);
}

/* ---------- model grid ---------- */
.model-grid{ display:grid; grid-template-columns:repeat(4,1fr); gap:20px; margin-bottom:26px; }
.model-card{
  border:1px solid var(--border); border-radius:var(--radius-md); padding:28px 22px; background:var(--surface);
  transition:transform .2s ease, border-color .2s ease, background .2s ease;
}
.model-card:hover{ transform:translateY(-4px); border-color:var(--border-strong); background:var(--surface-hover); }
.model-mark{
  width:44px; height:44px; border-radius:12px; display:flex; align-items:center; justify-content:center;
  font-family:var(--ff-display); font-weight:700; font-size:1.1rem; margin-bottom:18px;
  background:var(--grad-brand-soft); border:1px solid var(--border); color:var(--magenta-400);
}
.model-card h3{ font-size:1.05rem; margin-bottom:8px; }
.model-card p{ font-size:.88rem; color:var(--text-2); margin-bottom:16px; }
.model-badge{
  display:inline-flex; align-items:center; gap:6px; font-size:.72rem; font-weight:600; letter-spacing:.03em;
  color:#86efac; padding:5px 10px; border-radius:999px; background:rgba(134,239,172,.1); border:1px solid rgba(134,239,172,.25);
}
.model-badge::before{ content:""; width:6px; height:6px; border-radius:50%; background:#86efac; }
.model-disclaimer{ font-size:.78rem; color:var(--text-muted); max-width:720px; }

/* ---------- solutions ---------- */
.sol-list{ display:flex; flex-direction:column; }
.sol-row{ display:grid; grid-template-columns:90px 1fr; gap:0; padding:38px 0; border-top:1px solid var(--border); }
.sol-row:last-child{ border-bottom:1px solid var(--border); }
.sol-no{ font-family:var(--ff-display); font-size:1.6rem; font-weight:700; color:var(--purple-400); opacity:.55; }
.sol-body h3{ font-size:1.35rem; margin-bottom:12px; }
.sol-body p{ color:var(--text-2); max-width:640px; margin-bottom:18px; }
.sol-tags{ display:flex; flex-wrap:wrap; gap:9px; }
.sol-tags span{ font-size:.8rem; padding:7px 14px; border-radius:999px; border:1px solid var(--border); color:var(--text-2); }

/* ---------- card grids ---------- */
.card-grid{ display:grid; gap:20px; }
.card-grid--4{ grid-template-columns:repeat(4,1fr); }
.card-grid--3{ grid-template-columns:repeat(3,1fr); }
.ind-card, .why-card{
  border:1px solid var(--border); border-radius:var(--radius-md); padding:28px; background:var(--surface);
  transition:transform .2s ease, border-color .2s ease;
}
.ind-card:hover, .why-card:hover{ transform:translateY(-4px); border-color:var(--border-strong); }
.ind-icon{
  width:42px; height:42px; border-radius:11px; display:flex; align-items:center; justify-content:center;
  background:var(--grad-brand-soft); border:1px solid var(--border); color:var(--magenta-400); margin-bottom:18px;
}
.ind-card h3, .why-card h3{ font-size:1.05rem; margin-bottom:10px; }
.ind-card p, .why-card p{ font-size:.9rem; color:var(--text-2); }
.why-card{ position:relative; }
.why-card::before{ content:""; position:absolute; top:0; left:28px; width:28px; height:2px; background:var(--grad-brand); border-radius:2px; }
.why-card h3{ margin-top:14px; }

/* ---------- process ---------- */
.process-row{ display:grid; grid-template-columns:repeat(4,1fr); gap:24px; }
.process-step{ padding-top:20px; border-top:2px solid var(--border); position:relative; }
.process-no{ font-family:var(--ff-display); font-weight:700; color:var(--magenta-400); font-size:.95rem; margin-bottom:14px; }
.process-step h3{ font-size:1.1rem; margin-bottom:10px; }
.process-step p{ font-size:.88rem; color:var(--text-2); }

/* ---------- about ---------- */
.about-grid{ display:grid; grid-template-columns:1.1fr .9fr; gap:56px; align-items:start; }
.about-copy .section-title{ max-width:none; }
.about-copy p{ color:var(--text-2); font-size:1.02rem; margin-bottom:18px; }
.about-facts{ border:1px solid var(--border); border-radius:var(--radius-md); background:var(--surface); padding:8px 26px; }
.fact-row{ display:flex; justify-content:space-between; gap:20px; padding:18px 0; border-bottom:1px solid var(--border); font-size:.92rem; }
.fact-row:last-child{ border-bottom:none; }
.fact-row span{ color:var(--text-muted); }
.fact-row strong{ font-family:var(--ff-display); font-weight:600; text-align:right; }

/* ---------- cta band ---------- */
.cta-band{ padding:90px 0; text-align:center; }
.cta-inner{ max-width:620px; margin:0 auto; }
.cta-band h2{ font-size:clamp(1.9rem,3.6vw,2.6rem); margin-bottom:16px; }
.cta-band p{ color:var(--text-2); font-size:1.05rem; margin-bottom:34px; }

/* ---------- footer ---------- */
.site-footer{ border-top:1px solid var(--border); padding:64px 0 28px; }
.footer-grid{ display:grid; grid-template-columns:1.6fr 1fr 1fr 1fr; gap:40px; margin-bottom:48px; }
.footer-brand .brand-name{ font-family:var(--ff-display); font-weight:700; font-size:1.15rem; }
.footer-brand p{ color:var(--text-2); font-size:.86rem; margin:14px 0 10px; line-height:1.6; }
.footer-email{ font-size:.86rem; color:var(--text-2); }
.footer-email em{ display:block; color:var(--text-muted); font-style:normal; font-size:.78rem; margin-top:2px; }
.footer-col h4{ font-size:.82rem; text-transform:uppercase; letter-spacing:.08em; color:var(--text-muted); margin-bottom:16px; }
.footer-col a, .footer-link-btn{ display:block; color:var(--text-2); font-size:.9rem; padding:6px 0; background:none; border:none; text-align:left; }
.footer-col a:hover, .footer-link-btn:hover{ color:var(--text-1); }
.footer-note{ display:block; font-size:.78rem; color:var(--text-muted); margin-top:6px; }
.footer-bottom{
  display:flex; justify-content:space-between; flex-wrap:wrap; gap:10px; padding-top:24px; border-top:1px solid var(--border);
  font-size:.8rem; color:var(--text-muted);
}

/* ---------- back to top ---------- */
.back-top{
  position:fixed; bottom:26px; right:26px; z-index:40; width:44px; height:44px; border-radius:50%;
  background:rgba(20,10,30,.8); border:1px solid var(--border-strong); color:var(--text-1);
  display:flex; align-items:center; justify-content:center; backdrop-filter:blur(8px);
  opacity:0; transform:translateY(12px); pointer-events:none; transition:opacity .25s ease, transform .25s ease;
}
.back-top.show{ opacity:1; transform:none; pointer-events:auto; }
.back-top svg{ width:18px; height:18px; }

/* ---------- modal ---------- */
.modal{ position:fixed; inset:0; z-index:100; display:flex; align-items:center; justify-content:center; opacity:0; pointer-events:none; transition:opacity .25s ease; }
.modal[aria-hidden="false"]{ opacity:1; pointer-events:auto; }
.modal-backdrop{ position:absolute; inset:0; background:rgba(4,2,8,.75); backdrop-filter:blur(6px); }
.modal-panel{
  position:relative; width:min(480px, 92vw); max-height:88vh; overflow-y:auto; background:var(--bg-2);
  border:1px solid var(--border-strong); border-radius:var(--radius-lg); padding:36px; transform:translateY(14px); transition:transform .25s ease;
}
.modal[aria-hidden="false"] .modal-panel{ transform:none; }
.modal-panel h3{ font-size:1.35rem; margin-bottom:8px; }
.modal-panel > p{ color:var(--text-2); font-size:.92rem; margin-bottom:24px; }
.modal-close{ position:absolute; top:16px; right:16px; background:none; border:none; color:var(--text-2); font-size:1.6rem; line-height:1; }
#contactForm{ display:flex; flex-direction:column; gap:16px; }
#contactForm label{ display:flex; flex-direction:column; gap:7px; font-size:.85rem; color:var(--text-2); }
#contactForm input, #contactForm textarea{
  background:rgba(255,255,255,.04); border:1px solid var(--border); border-radius:var(--radius-sm);
  padding:12px 14px; color:var(--text-1); font-family:var(--ff-body); font-size:.94rem; resize:vertical;
}
#contactForm input:focus, #contactForm textarea:focus{ outline:none; border-color:var(--magenta-500); }
.form-ok{ font-size:.85rem; color:var(--magenta-400); margin-top:4px; }

/* ---------- responsive ---------- */
@media (max-width: 980px){
  .stats-grid{ grid-template-columns:repeat(2,1fr); }
  .card-grid--4{ grid-template-columns:repeat(2,1fr); }
  .card-grid--3{ grid-template-columns:repeat(2,1fr); }
  .model-grid{ grid-template-columns:repeat(2,1fr); }
  .process-row{ grid-template-columns:repeat(2,1fr); }
  .about-grid{ grid-template-columns:1fr; }
  .zetastack{ grid-template-columns:1fr; }
  .zetastack-layers{ border-right:none; border-bottom:1px solid var(--border); }
  .footer-grid{ grid-template-columns:1fr 1fr; }
}

@media (max-width: 720px){
  .main-nav{
    position:fixed; top:76px; left:0; right:0; bottom:0; background:rgba(6,3,12,.98); backdrop-filter:blur(14px);
    flex-direction:column; align-items:flex-start; padding:32px 28px; gap:22px; transform:translateX(100%);
    transition:transform .28s ease;
  }
  .main-nav.open{ transform:none; }
  .burger{ display:flex; }
  .stats-grid{ grid-template-columns:1fr 1fr; gap:32px 20px; }
  .card-grid--4, .card-grid--3, .model-grid, .process-row{ grid-template-columns:1fr; }
  .footer-grid{ grid-template-columns:1fr; gap:32px; }
  .sol-row{ grid-template-columns:1fr; gap:10px; }
}