/* HeLink website — single sheet, light-on-aurora gradient theme. */

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: "Microsoft YaHei UI", "PingFang SC", system-ui, -apple-system,
               "Segoe UI", Arial, sans-serif;
  color: #1E293B;
  background: #FAFAFC;
  line-height: 1.6;
}
.wrap { max-width: 1080px; margin: 0 auto; padding: 0 24px; }

/* ---------- nav ---------- */
.nav {
  position: sticky; top: 0; z-index: 50;
  background: rgba(255,255,255,0.92);
  backdrop-filter: saturate(180%) blur(10px);
  -webkit-backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid #E2E8F0;
}
.nav .wrap { display: flex; align-items: center; justify-content: space-between; height: 64px; }
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; color: inherit; }
.brand-text { font-size: 18px; font-weight: 600; letter-spacing: 0.5px; }
.brand-text em { font-style: normal; font-weight: 500; color: #6366F1; margin-left: 4px; }
.nav-links { display: flex; gap: 24px; }
.nav-links a {
  color: #475569; text-decoration: none; font-size: 14px;
  transition: color 0.15s;
}
.nav-links a:hover { color: #6366F1; }

/* ---------- hero ---------- */
.hero {
  padding: 96px 0 80px;
  background:
    radial-gradient(1100px 600px at 90% -100px, rgba(192,38,211,0.20), transparent 60%),
    radial-gradient(900px 500px at 10% 60%, rgba(6,182,212,0.18), transparent 60%),
    linear-gradient(180deg, #F5F3FF 0%, #FAFAFC 100%);
}
.hero h1 {
  font-size: 56px; font-weight: 700;
  letter-spacing: -1px; line-height: 1.15;
  color: #0F172A;
}
.hero .tagline {
  margin-top: 18px; font-size: 19px; color: #475569; max-width: 640px;
}
.cta-row { margin-top: 36px; display: flex; gap: 14px; flex-wrap: wrap; }
.btn {
  display: inline-flex; align-items: center; justify-content: center;
  padding: 12px 26px; border-radius: 10px; text-decoration: none;
  font-weight: 600; font-size: 15px;
  transition: transform 0.1s, box-shadow 0.2s, background 0.2s;
}
.btn.primary {
  background: linear-gradient(135deg, #06B6D4 0%, #6366F1 60%, #C026D3 100%);
  color: white;
  box-shadow: 0 4px 16px rgba(99,102,241,0.30);
}
.btn.primary:hover { transform: translateY(-1px); box-shadow: 0 8px 22px rgba(99,102,241,0.40); }
.btn.ghost {
  background: white; color: #1E293B; border: 1px solid #CBD5E1;
}
.btn.ghost:hover { border-color: #6366F1; color: #6366F1; }
.btn.big { padding: 16px 32px; font-size: 16px; }
.dl-buttons { display: flex; flex-direction: column; gap: 12px; flex-shrink: 0; }
.dl-buttons .btn { white-space: nowrap; min-width: 220px; justify-content: center; }
@media (max-width: 720px) { .dl-buttons { width: 100%; } .dl-buttons .btn { width: 100%; } }
.hero .micro { margin-top: 22px; color: #64748B; font-size: 13px; }

/* ---------- features ---------- */
.features { padding: 90px 0; }
.features h2, .download h2, .faq h2 {
  font-size: 32px; font-weight: 700; color: #0F172A;
  text-align: center; margin-bottom: 50px;
  letter-spacing: -0.5px;
}
.grid {
  display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px;
}
.card {
  background: white; border: 1px solid #E2E8F0; border-radius: 14px;
  padding: 28px 24px;
  transition: transform 0.15s, box-shadow 0.2s, border-color 0.15s;
}
.card:hover {
  transform: translateY(-3px);
  box-shadow: 0 12px 28px rgba(15,23,42,0.08);
  border-color: #C7D2FE;
}
.card .icon { font-size: 28px; margin-bottom: 12px; }
.card h3 { font-size: 17px; margin-bottom: 8px; color: #0F172A; }
.card p { font-size: 14px; color: #64748B; line-height: 1.65; }

/* ---------- download ---------- */
.download {
  padding: 90px 0;
  background: linear-gradient(180deg, #FAFAFC 0%, #F1F5F9 100%);
}
.dl-card {
  display: flex; align-items: center; justify-content: space-between;
  background: white; border: 1px solid #E2E8F0; border-radius: 16px;
  padding: 34px 38px; gap: 30px;
  box-shadow: 0 10px 30px rgba(15,23,42,0.04);
  flex-wrap: wrap;
}
.dl-info { flex: 1 1 320px; }
.dl-info h3 { font-size: 22px; margin-bottom: 6px; color: #0F172A; }
.dl-info > p { color: #64748B; font-size: 14px; margin-bottom: 16px; }
.ticks { list-style: none; padding: 0; }
.ticks li {
  padding-left: 22px; position: relative; color: #475569;
  font-size: 14px; line-height: 1.9;
}
.ticks li::before {
  content: "✓"; position: absolute; left: 0; color: #10B981; font-weight: 700;
}
.micro.center { text-align: center; color: #94A3B8; margin-top: 24px; font-size: 13px; }
.micro a { color: #6366F1; text-decoration: none; }
.micro a:hover { text-decoration: underline; }

/* ---------- FAQ ---------- */
.faq { padding: 90px 0; }
.faq details {
  background: white; border: 1px solid #E2E8F0; border-radius: 12px;
  padding: 18px 24px; margin-bottom: 12px;
  transition: border-color 0.15s, box-shadow 0.2s;
}
.faq details[open] { border-color: #C7D2FE; box-shadow: 0 6px 18px rgba(99,102,241,0.06); }
.faq summary {
  cursor: pointer; font-weight: 600; color: #1E293B;
  list-style: none; outline: none;
  font-size: 15px;
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::before {
  content: "+"; display: inline-block; width: 22px; color: #6366F1;
  font-weight: 700; transition: transform 0.2s;
}
.faq details[open] summary::before { content: "−"; }
.faq details > p {
  margin-top: 12px; padding-left: 22px; color: #475569;
  font-size: 14px; line-height: 1.7;
}
.faq a { color: #6366F1; }

/* ---------- footer ---------- */
footer {
  background: #0F172A; color: #94A3B8; padding: 60px 0 30px;
}
footer .brand-text { color: white; }
footer .brand-text em { color: #818CF8; }
.footer-grid {
  display: grid; grid-template-columns: 2fr 1fr 1fr; gap: 40px;
  margin-bottom: 40px;
}
.footer-grid h4 { color: #E2E8F0; font-size: 14px; margin-bottom: 12px; font-weight: 600; }
.footer-grid ul { list-style: none; }
.footer-grid li { margin-bottom: 8px; }
.footer-grid a { color: #94A3B8; text-decoration: none; font-size: 14px; }
.footer-grid a:hover { color: white; }
.muted { color: #64748B; font-size: 13px; }
.copyright {
  border-top: 1px solid #1E293B; padding-top: 22px;
  text-align: center; color: #64748B; font-size: 13px;
}

/* ---------- responsive ---------- */
@media (max-width: 720px) {
  .hero { padding: 64px 0 56px; }
  .hero h1 { font-size: 38px; }
  .hero .tagline { font-size: 16px; }
  .grid { grid-template-columns: 1fr; }
  .dl-card { padding: 24px 22px; }
  .btn.big { width: 100%; }
  .footer-grid { grid-template-columns: 1fr; gap: 28px; }
  .nav-links { gap: 14px; }
  .nav-links a { font-size: 13px; }
}