/* ---------- 4. Header sticky ---------- */
header{
  position:sticky;top:0;z-index:100;
  backdrop-filter:saturate(180%) blur(16px);
  -webkit-backdrop-filter:saturate(180%) blur(16px);
  background:rgba(246,245,241,.78);
  border-bottom:1px solid var(--line);
}
.nav{display:flex;align-items:center;justify-content:space-between;height:74px}
.brand{display:flex;align-items:center;gap:12px;font-family:var(--font-ui);font-weight:700;font-size:1.18rem;letter-spacing:-.01em}
.logo-mark{
  width:42px;height:42px;border-radius:13px;flex:0 0 auto;
  background:linear-gradient(150deg,var(--indigo),#6a4bff);
  display:grid;place-items:center;box-shadow:0 8px 22px -8px rgba(58,58,255,.6);
}
.brand b{color:var(--indigo)}
.nav-links{display:flex;align-items:center;gap:34px;font-family:var(--font-ui);font-weight:500;font-size:.96rem}
.nav-links a{color:var(--ink-soft);transition:color .2s;position:relative}
.nav-links a:hover{color:var(--ink)}
.nav-links a::after{content:"";position:absolute;left:0;bottom:-6px;width:0;height:2px;background:var(--indigo);transition:width .25s}
.nav-links a:hover::after{width:100%}
.nav-cta{
  background:linear-gradient(150deg,var(--indigo),#6a4bff);color:#fff !important;padding:11px 22px;border-radius:12px;
  font-family:var(--font-ui);font-weight:600;font-size:.92rem;transition:transform .2s,box-shadow .2s;
  box-shadow:0 8px 22px -8px rgba(58,58,255,.6);
}
.nav-cta:hover{transform:translateY(-2px);box-shadow:0 12px 28px -8px rgba(58,58,255,.75);color:#fff !important}
.burger{display:none;width:44px;height:44px;border-radius:12px;border:1px solid var(--line);background:var(--card)}
.burger span{display:block;width:18px;height:2px;background:var(--ink);margin:3px auto;border-radius:2px}