/* 基础样式 */
:root {
  --bg: #0b1220;
  --bg-soft: #0f1730;
  --card: #111a36;
  --text: #e8edf7;
  --muted: #9fb0d3;
  --brand: #5b8cff;
  --brand-600: #3e6ef1;
  --accent: #20d0b3;
  --shadow: 0 10px 30px rgba(0,0,0,.3);
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji", "Segoe UI Emoji";
  color: var(--text);
  background: linear-gradient(180deg, var(--bg) 0%, var(--bg-soft) 100%);
}

.container {
  width: min(1120px, 92%);
  margin: 0 auto;
}

.btn {
  display: inline-block;
  padding: 12px 18px;
  border-radius: 10px;
  text-decoration: none;
  font-weight: 600;
  transition: transform .12s ease, box-shadow .2s ease, background .2s ease;
}
.btn:hover { transform: translateY(-1px); }
.btn:active { transform: translateY(0); }
.btn-primary {
  background: linear-gradient(135deg, var(--brand), var(--accent));
  color: #0b1220;
  box-shadow: var(--shadow);
}
.btn-outline {
  color: var(--text);
  border: 1px solid rgba(255,255,255,.14);
  background: rgba(255,255,255,.02);
}

.section { padding: 72px 0; }
.section-title { font-size: 28px; margin: 0 0 24px; }
.subtitle { color: var(--muted); }
.list { margin: 12px 0 0; padding-left: 18px; color: var(--muted); }
.list li { margin: 6px 0; }
.muted { color: var(--muted); }

/* 头部导航 */
.site-header { position: sticky; top: 0; z-index: 20; background: rgba(11,18,32,.6); backdrop-filter: saturate(140%) blur(10px); border-bottom: 1px solid rgba(255,255,255,.08); }
.header-inner { display: flex; align-items: center; justify-content: space-between; height: 64px; }
.brand { color: var(--text); text-decoration: none; display: inline-flex; align-items: center; gap: 10px; }
.logo { display: inline-block; font-weight: 800; letter-spacing: .5px; background: linear-gradient(135deg, var(--brand), var(--accent)); -webkit-background-clip: text; background-clip: text; color: transparent; font-size: 20px; }

.nav { position: relative; }
.nav-list { list-style: none; display: flex; gap: 20px; margin: 0; padding: 0; }
.nav-list a { color: var(--text); text-decoration: none; font-weight: 600; opacity: .9; }
.nav-list a:hover { opacity: 1; }
.nav-toggle { display: none; width: 40px; height: 40px; border-radius: 8px; border: 1px solid rgba(255,255,255,.12); background: rgba(255,255,255,.04); align-items: center; justify-content: center; }
.nav-toggle .bar { width: 20px; height: 2px; background: var(--text); margin: 3px 0; display: block; }

/* Hero */
.hero { position: relative; overflow: hidden; padding: 88px 0 72px; }
.hero-inner { text-align: center; }
.hero h1 { font-size: clamp(28px, 4.5vw, 44px); margin: 0 0 12px; }
.hero .subtitle { font-size: 16px; margin: 0 auto 22px; width: min(760px, 92%); }
.hero-ctas { display: flex; gap: 12px; align-items: center; justify-content: center; }
.hero-bg { position: absolute; inset: 0; background:
  radial-gradient(720px 220px at 20% 0%, rgba(91,140,255,.22), transparent 60%),
  radial-gradient(720px 220px at 80% 0%, rgba(32,208,179,.16), transparent 60%);
  pointer-events: none;
}

/* Features */
.features { background: linear-gradient(180deg, rgba(255,255,255,.02), rgba(255,255,255,0) 30%); }
.features-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.card { background: var(--card); border: 1px solid rgba(255,255,255,.08); border-radius: 14px; padding: 18px; box-shadow: var(--shadow); }
.card h3 { margin: 0 0 8px; font-size: 18px; }
.card p { margin: 0; color: var(--muted); }

/* About */
.about-inner { display: grid; grid-template-columns: 1.1fr .9fr; gap: 24px; align-items: center; }
.about-illu { height: 260px; border-radius: 14px; background:
  conic-gradient(from 180deg at 50% 50%, rgba(91,140,255,.18), rgba(32,208,179,.16), rgba(91,140,255,.18));
  border: 1px solid rgba(255,255,255,.1);
  box-shadow: var(--shadow);
}

/* FAQs */
.accordion { display: grid; gap: 12px; }
.accordion-item { background: var(--card); border: 1px solid rgba(255,255,255,.08); border-radius: 12px; overflow: hidden; }
.accordion-header { width: 100%; text-align: left; padding: 14px 16px; background: transparent; color: var(--text); font-weight: 600; border: 0; cursor: pointer; display: flex; align-items: center; justify-content: space-between; }
.accordion-header::after { content: "+"; color: var(--muted); font-weight: 700; }
.accordion-item[open] .accordion-header::after,
.accordion-item.active .accordion-header::after { content: "−"; }
.accordion-panel { display: none; padding: 0 16px 14px; color: var(--muted); }
.accordion-item.active .accordion-panel { display: block; }

/* Contact */
.contact-inner { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; }
.contact-form { background: var(--card); border: 1px solid rgba(255,255,255,.08); border-radius: 12px; padding: 16px; }
.contact-form label { display: grid; gap: 6px; margin-bottom: 10px; }
.contact-form input, .contact-form textarea { width: 100%; padding: 10px 12px; border-radius: 8px; border: 1px solid rgba(255,255,255,.12); background: rgba(255,255,255,.02); color: var(--text); }
.form-tip { margin: 8px 0 0; color: var(--accent); min-height: 20px; }

/* Footer */
.site-footer { padding: 28px 0 40px; border-top: 1px solid rgba(255,255,255,.08); background: rgba(0,0,0,.18); }
.site-footer p { margin: 6px 0; color: var(--muted); }

/* 响应式 */
@media (max-width: 960px) {
  .features-grid { grid-template-columns: 1fr 1fr; }
  .about-inner { grid-template-columns: 1fr; }
  .contact-inner { grid-template-columns: 1fr; }
}

@media (max-width: 720px) {
  .section { padding: 56px 0; }
  .nav-toggle { display: inline-flex; }
  .nav-list { position: absolute; right: 0; top: 52px; background: rgba(15,23,48,.96); border: 1px solid rgba(255,255,255,.1); border-radius: 12px; padding: 10px; display: none; flex-direction: column; gap: 6px; min-width: 160px; }
  .nav-list.show { display: flex; }
}