/* 子页面共用样式：关于 / 常见问题 / 联系我们
   设计语言与 index.html 保持一致（玻璃顶栏、渐变卡片、主题切换）。 */
:root {
  --bg: #0b0f17;
  --surface: #131a26;
  --surface-2: #1a2230;
  --border: #26304180;
  --text: #e6ebf5;
  --muted: #8b97ad;
  --acc: #818cf8;
  --acc-2: #34d399;
  --card-shadow: 0 10px 30px -12px rgba(0, 0, 0, .55);
  --radius: 16px;
}
[data-theme="light"] {
  --bg: #f4f6fb;
  --surface: #ffffff;
  --surface-2: #eef1f8;
  --border: #d8deea;
  --text: #1a2030;
  --muted: #5b6478;
  --acc: #6366f1;
  --acc-2: #059669;
  --card-shadow: 0 10px 30px -14px rgba(20, 30, 60, .22);
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
  transition: background .25s ease, color .25s ease;
}
a { color: inherit; text-decoration: none; }

/* ---------- 玻璃顶栏 ---------- */
header {
  position: sticky; top: 0; z-index: 50;
  display: flex; align-items: center; gap: 16px;
  padding: 14px 24px;
  background: var(--surface);
  background: color-mix(in srgb, var(--surface) 72%, transparent);
  backdrop-filter: saturate(160%) blur(14px);
  -webkit-backdrop-filter: saturate(160%) blur(14px);
  border-bottom: 1px solid var(--border);
}
.brand { display: flex; align-items: center; gap: 10px; font-weight: 800; font-size: 18px; letter-spacing: .2px; white-space: nowrap; }
.brand .logo { height: 34px; width: auto; border-radius: 6px; display: block; filter: drop-shadow(0 4px 12px -4px var(--acc)); }
[data-theme="light"] .brand .logo { filter: none; }
.brand .name b { color: var(--acc); }
.topbar-spacer { flex: 1; }
.back-link {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 8px 12px; border-radius: 10px;
  color: var(--muted); font-size: 14px; font-weight: 600; transition: .18s;
}
.back-link:hover { color: var(--text); background: var(--surface-2); }
.icon-btn {
  width: 38px; height: 38px; border-radius: 10px;
  display: grid; place-items: center; cursor: pointer;
  background: var(--surface-2); border: 1px solid var(--border);
  color: var(--text); font-size: 17px; transition: .18s;
}
.icon-btn:hover { border-color: var(--acc); color: var(--acc); }

/* ---------- 标题区 ---------- */
.subhero { max-width: 760px; margin: 42px auto 6px; padding: 0 24px; text-align: center; }
.subhero h1 {
  margin: 0 0 10px; font-size: clamp(26px, 3.5vw, 34px); font-weight: 850; letter-spacing: -.3px;
  background: linear-gradient(120deg, var(--text), var(--acc) 70%, var(--acc-2));
  -webkit-background-clip: text; background-clip: text; color: var(--text); -webkit-text-fill-color: transparent;
}
.subhero p { color: var(--muted); margin: 0; font-size: 15px; }

.container { max-width: 820px; margin: 26px auto 0; padding: 0 24px 64px; }

/* ---------- 卡片 ---------- */
.card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 22px 24px; box-shadow: var(--card-shadow);
}
.card + .card { margin-top: 18px; }
.card h2 { display: flex; align-items: center; gap: 10px; margin: 0 0 14px; font-size: 20px; font-weight: 800; letter-spacing: .2px; }
.card h2::before { content: ""; width: 5px; height: 20px; border-radius: 3px; background: linear-gradient(180deg, var(--acc), var(--acc-2)); }
.card p { color: var(--muted); line-height: 1.85; margin: 0 0 12px; font-size: 15px; }
.card p:last-child { margin-bottom: 0; }
.card a { color: var(--acc); font-weight: 600; }
.card ul { color: var(--muted); line-height: 1.9; margin: 4px 0 12px; padding-left: 20px; font-size: 15px; }
.card ul:last-child { margin-bottom: 0; }

/* 价值点 pill */
.stats { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 16px; }
.stat {
  display: inline-flex; align-items: center; gap: 7px;
  padding: 7px 14px; border-radius: 999px;
  background: var(--surface-2); border: 1px solid var(--border);
  font-size: 13px; font-weight: 600; color: var(--text);
}
.stat .em { color: var(--acc); }

/* ---------- FAQ ---------- */
.faq-list { display: flex; flex-direction: column; gap: 12px; }
.faq-item {
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--surface); overflow: hidden;
  transition: border-color .18s ease, box-shadow .18s ease;
}
.faq-item[open] { border-color: color-mix(in srgb, var(--acc) 45%, var(--border)); box-shadow: var(--card-shadow); }
.faq-item summary {
  list-style: none; cursor: pointer;
  display: flex; align-items: center; justify-content: space-between; gap: 12px;
  padding: 16px 18px; font-weight: 700; font-size: 15.5px; color: var(--text);
  transition: color .18s ease;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary:hover { color: var(--acc); }
.faq-item summary .q-ico {
  flex: 0 0 auto; width: 22px; height: 22px; border-radius: 7px;
  display: grid; place-items: center; font-size: 15px; line-height: 1; color: var(--acc);
  background: color-mix(in srgb, var(--acc) 16%, var(--surface-2));
  transition: transform .22s ease;
}
.faq-item[open] summary .q-ico { transform: rotate(45deg); }
.faq-item .a { color: var(--muted); line-height: 1.85; margin: 0; padding: 0 18px 16px; font-size: 14.5px; }

/* ---------- 联系我们 ---------- */
.contact-list { display: flex; flex-direction: column; gap: 12px; margin-top: 6px; }
.contact-row {
  display: flex; align-items: center; gap: 14px;
  padding: 14px 16px; border: 1px solid var(--border); border-radius: 12px;
  background: var(--surface-2);
}
.contact-row .ci {
  flex: 0 0 auto; width: 42px; height: 42px; border-radius: 11px;
  display: grid; place-items: center; font-size: 20px;
  background: color-mix(in srgb, var(--acc) 16%, var(--surface)); border: 1px solid var(--border);
}
.contact-row .ct { min-width: 0; }
.contact-row .ct .k { font-size: 12px; color: var(--muted); }
.contact-row .ct .v { font-size: 15px; font-weight: 700; color: var(--text); }
.contact-row .ct .v a { color: var(--acc); }

/* ---------- 底部跳转按钮（用于首页） ---------- */
.btn-row { display: flex; flex-wrap: wrap; gap: 12px; justify-content: center; margin-top: 34px; padding: 0 24px; }
.big-btn {
  display: inline-flex; align-items: center; gap: 10px;
  padding: 14px 22px; border-radius: 14px;
  font-weight: 700; font-size: 15px; color: #fff;
  background: linear-gradient(135deg, var(--acc), var(--acc-2));
  border: 1px solid transparent; box-shadow: var(--card-shadow);
  transition: transform .16s ease, box-shadow .16s ease; cursor: pointer;
}
.big-btn:hover { transform: translateY(-2px); }

footer { text-align: center; color: var(--muted); font-size: 12.5px; padding: 26px 16px 40px; }
footer a { color: var(--acc); }

@media (max-width: 640px) {
  header { padding: 12px 14px; gap: 10px; }
  .brand .name { display: none; }
  .subhero, .container, .btn-row { padding-left: 14px; padding-right: 14px; }
}