/* 基础样式与暗色模式 */
:root {
  --bg: #0b0d12;
  --bg-alt: #0f1218;
  --fg: #e6e9ef;
  --muted: #a6adbb;
  --brand: #7c5cff;
  --brand-2: #00d1b2;
  --card: #151924;
  --border: #1f2430;
  --shadow: 0 10px 30px rgba(0,0,0,.35);
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  color: var(--fg);
  background: radial-gradient(1200px 600px at 15% -10%, rgba(124,92,255,.22), transparent 60%),
              radial-gradient(900px 500px at 90% 0%, rgba(0,209,178,.18), transparent 55%),
              var(--bg);
  font: 16px/1.6 system-ui, -apple-system, "Segoe UI", Roboto, "PingFang SC", "Noto Sans CJK SC", "Microsoft YaHei", Arial, sans-serif;
}

.container { width: min(1100px, 92%); margin: 0 auto; }

/* 头部 */
.site-header {
  position: sticky; top: 0; z-index: 20;
  backdrop-filter: saturate(140%) blur(12px);
  background: rgba(11,13,18,.6);
  border-bottom: 1px solid var(--border);
}
.header-inner { display: flex; align-items: center; justify-content: space-between; padding: 10px 0; }
.brand { display: inline-flex; align-items: center; gap: 10px; font-weight: 700; letter-spacing: .3px; }
.logo { display: inline-grid; place-items: center; width: 28px; height: 28px; border-radius: 8px; background: linear-gradient(135deg, var(--brand), var(--brand-2)); }
.brand-name { font-size: 18px; }
.nav { display: flex; align-items: center; gap: 14px; }
.nav a { color: var(--muted); text-decoration: none; padding: 8px 10px; border-radius: 8px; }
.nav a:hover { color: var(--fg); background: var(--bg-alt); }

/* 按钮 */
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; padding: 10px 16px; border-radius: 10px; border: 1px solid var(--border); color: var(--fg); background: var(--bg-alt); text-decoration: none; box-shadow: var(--shadow); }
.btn.primary { border-color: transparent; background: linear-gradient(135deg, var(--brand), var(--brand-2)); color: #0b0d12; font-weight: 700; }
.btn.ghost { background: transparent; box-shadow: none; }
.btn:hover { transform: translateY(-1px); }

/* Hero */
.hero { position: relative; padding: 68px 0 40px; }
.hero-inner { text-align: center; }
.hero h1 { margin: 0 0 10px; font-size: clamp(28px, 4.5vw, 44px); letter-spacing: .2px; }
.lead { color: var(--muted); font-size: 18px; margin: 0 auto 24px; width: min(800px, 96%); }
.cta-group { display: inline-flex; gap: 12px; flex-wrap: wrap; }
.hero-decoration { position: absolute; inset: 0; pointer-events: none; }

/* 通用分节 */
.section { padding: 56px 0; }
.section.alt { background: linear-gradient(180deg, rgba(255,255,255,0.02), transparent 35%), var(--bg-alt); border-top: 1px solid var(--border); border-bottom: 1px solid var(--border); }
.section h2 { margin: 0 0 18px; font-size: 24px; }

/* 卡片网格 */
.features-grid { list-style: none; padding: 0; margin: 14px 0 0; display: grid; grid-template-columns: repeat(auto-fit, minmax(230px,1fr)); gap: 14px; }
.card { background: var(--card); border: 1px solid var(--border); border-radius: 14px; padding: 16px; box-shadow: var(--shadow); }
.card h3 { margin: 0 0 6px; font-size: 18px; }
.card p { margin: 0; color: var(--muted); }

/* 步骤 */
.steps { margin: 10px 0 0; padding-left: 20px; }
.steps li { margin: 8px 0 10px; }
.note { margin-top: 10px; color: var(--muted); font-size: 14px; }

/* 场景 */
.scenarios { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px,1fr)); gap: 14px; }

/* FAQ */
details { background: var(--card); border: 1px solid var(--border); border-radius: 12px; padding: 12px 14px; margin: 10px 0; }
details summary { cursor: pointer; font-weight: 600; }

/* 底部 */
.site-footer { border-top: 1px solid var(--border); background: var(--bg-alt); padding: 22px 0; color: var(--muted); text-align: center; }

/* 返回顶部 */
.back-to-top { position: fixed; right: 18px; bottom: 18px; width: 40px; height: 40px; border-radius: 10px; border: 1px solid var(--border); background: var(--card); color: var(--fg); display: grid; place-items: center; opacity: 0; pointer-events: none; transition: opacity .2s ease, transform .2s ease; box-shadow: var(--shadow); }
.back-to-top.show { opacity: 1; pointer-events: auto; transform: translateY(-2px); }

/* 可访问性与焦点可见 */
:focus { outline: 2px solid color-mix(in srgb, var(--brand) 60%, white); outline-offset: 2px; border-radius: 6px; }

@media (max-width: 640px) {
  .nav a { display: none; }
}