/* Bifrost 官网样式（2026-10 改版）。浅色主题：钴蓝 + 冷白 + 冰蓝，红色 Logo 只做品牌识别。 */
:root {
  --ink: #0d1a33;
  --ink-2: #33415c;
  --muted: #55627a;
  --line: #dfe6f3;
  --line-2: #eef2f9;
  --bg: #ffffff;
  --ice: #f5f8ff;
  --ice-2: #eaf1ff;
  --cobalt: #2457e6;
  --cobalt-d: #1a43b8;
  --cobalt-l: #dbe6ff;
  --red: #e5302d;
  --radius: 18px;
  --shadow: 0 1px 2px rgba(13, 26, 51, .06), 0 12px 32px -12px rgba(13, 26, 51, .18);
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "PingFang TC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC", "Noto Sans SC", Roboto, "Helvetica Neue", Arial, sans-serif;
  color-scheme: light;
}
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; scroll-padding-top: 84px; }
body { margin: 0; background: var(--bg); color: var(--ink); font: 16px/1.7 var(--font); -webkit-font-smoothing: antialiased; overflow-x: hidden; }
html[lang="zh-Hant"] body { font-family: -apple-system, BlinkMacSystemFont, "PingFang TC", "Microsoft JhengHei", "Noto Sans CJK TC", "Noto Sans TC", "Segoe UI", Roboto, Arial, sans-serif; }
img { max-width: 100%; height: auto; display: block; }
a { color: var(--cobalt); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }
:focus-visible { outline: 3px solid var(--cobalt); outline-offset: 2px; border-radius: 6px; }
h1, h2, h3 { margin: 0; line-height: 1.2; letter-spacing: -.01em; }
h2 { font-size: clamp(28px, 4vw, 42px); font-weight: 800; }
h3 { font-size: 18px; font-weight: 700; }
p { margin: 0; }
.wrap { width: min(1180px, 100% - 40px); margin-inline: auto; }
.narrow { width: min(860px, 100% - 40px); }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.skip { position: absolute; left: 12px; top: -60px; z-index: 50; background: var(--ink); color: #fff; padding: 8px 14px; border-radius: 8px; }
.skip:focus { top: 12px; }
.sub { color: var(--muted); font-size: 17px; margin-top: 12px; max-width: 46em; }

/* ---------- 顶栏 ---------- */
.topbar { position: sticky; top: 0; z-index: 30; background: rgba(255, 255, 255, .86); backdrop-filter: saturate(1.4) blur(14px); -webkit-backdrop-filter: saturate(1.4) blur(14px); border-bottom: 1px solid var(--line-2); }
.topbar-in { display: flex; align-items: center; gap: 20px; height: 64px; }
.brand { display: inline-flex; align-items: center; gap: 10px; color: var(--ink); font-weight: 800; font-size: 20px; letter-spacing: -.02em; }
.brand:hover { text-decoration: none; }
.brand img { width: 32px; height: 32px; border-radius: 9px; }
.nav { display: flex; align-items: center; gap: 26px; margin-left: auto; font-size: 15px; }
.nav > a { color: var(--ink-2); font-weight: 600; }
.nav > a:hover { color: var(--cobalt); text-decoration: none; }
.langs { display: inline-flex; gap: 2px; padding: 3px; background: var(--ice); border-radius: 999px; }
.langs a { padding: 3px 10px; border-radius: 999px; color: var(--muted); font-size: 13px; font-weight: 600; }
.langs a[aria-current] { background: #fff; color: var(--ink); box-shadow: 0 1px 2px rgba(13, 26, 51, .1); }
.langs a:hover { text-decoration: none; color: var(--ink); }
.menu-btn { display: none; }

/* ---------- 按钮 ---------- */
.btn { display: inline-flex; align-items: center; justify-content: center; border-radius: 999px; font-weight: 700; }
.btn-sm { padding: 8px 16px; font-size: 14px; }
.btn-primary { background: var(--cobalt); color: #fff; }
.btn-primary:hover { background: var(--cobalt-d); text-decoration: none; }
.stores { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 10px; }
.store { display: flex; flex-direction: column; justify-content: center; min-height: 58px; padding: 9px 18px; border-radius: 14px; line-height: 1.25; transition: transform .15s ease, background-color .15s ease; }
.store:hover { text-decoration: none; transform: translateY(-1px); }
.store-name { font-weight: 800; font-size: 16px; }
.store-sub { font-size: 12.5px; opacity: .92; }
.store.btn-primary { background: var(--cobalt); color: #fff; }
.store.btn-dark { background: var(--ink); color: #fff; }
.store.btn-dark:hover { background: #1d2c4b; }
.store.btn-primary .store-sub { opacity: 1; }
.store.is-suggested { outline: 3px solid var(--cobalt-l); outline-offset: 2px; }

/* ---------- 首屏 ---------- */
.hero { position: relative; overflow: hidden; background:
  radial-gradient(900px 480px at 85% 10%, var(--ice-2) 0%, rgba(234, 241, 255, 0) 70%),
  linear-gradient(180deg, var(--ice) 0%, #fff 100%); }
.hero-in { display: grid; grid-template-columns: minmax(0, 1.08fr) minmax(0, .92fr); gap: 40px; align-items: center; padding: 64px 0 72px; }
.eyebrow { display: inline-block; font-size: 13px; font-weight: 700; color: var(--cobalt); background: #fff; border: 1px solid var(--cobalt-l); padding: 4px 12px; border-radius: 999px; letter-spacing: .02em; }
.hero h1 { margin-top: 22px; display: flex; flex-direction: column; gap: 6px; }
.wordmark { font-size: clamp(64px, 10vw, 128px); font-weight: 900; letter-spacing: -.045em; line-height: .95; color: var(--ink); }
.h1-sub { font-size: clamp(24px, 3.2vw, 36px); font-weight: 800; color: var(--cobalt); letter-spacing: -.01em; }
.tagline { margin-top: 18px; font-size: clamp(19px, 2.2vw, 24px); font-weight: 700; color: var(--ink); }
.lead { margin-top: 12px; font-size: 17px; color: var(--ink-2); max-width: 36em; }
.hero-stores { margin-top: 28px; max-width: 520px; }
.hero-meta { margin-top: 16px; font-size: 14px; color: var(--muted); }
.hero-art { position: relative; height: 560px; }
.bridge { position: absolute; left: -6%; right: -6%; bottom: 8%; width: 112%; height: auto; }
.phone { border-radius: 30px; box-shadow: 0 30px 60px -24px rgba(13, 26, 51, .38), 0 0 0 1px rgba(13, 26, 51, .06); background: #fff; }
.phone-front { position: absolute; width: 300px; left: 50%; top: 10px; transform: translateX(-28%); }
.phone-back { position: absolute; width: 240px; left: 50%; top: 70px; transform: translateX(-118%) rotate(-5deg); opacity: .96; }

/* ---------- 是什么 ---------- */
.what { padding: 88px 0 72px; }
.what h2 { font-size: clamp(30px, 4.4vw, 46px); }
.big { margin-top: 18px; font-size: clamp(18px, 2vw, 21px); line-height: 1.75; color: var(--ink-2); }
.big strong { color: var(--ink); }
.facts { margin: 34px 0 0; display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; }
.facts div { padding: 18px 20px; border-left: 1px solid var(--line); }
.facts div:first-child { border-left: 0; }
.facts dt { font-size: 13px; color: var(--muted); font-weight: 600; }
.facts dd { margin: 4px 0 0; font-size: 18px; font-weight: 800; color: var(--ink); line-height: 1.35; }

/* ---------- 步骤 ---------- */
.how { padding: 80px 0; background: var(--ice); }
.how-in { display: grid; grid-template-columns: minmax(0, 1.2fr) minmax(0, .8fr); gap: 56px; align-items: center; }
.steps { list-style: none; padding: 0; margin: 32px 0 0; display: grid; gap: 14px; }
.steps li { display: grid; grid-template-columns: 44px 1fr; gap: 16px; align-items: start; background: #fff; border: 1px solid var(--line); border-radius: var(--radius); padding: 18px 20px; }
.steps .num { width: 36px; height: 36px; border-radius: 50%; display: grid; place-items: center; background: var(--cobalt); color: #fff; font-weight: 800; font-size: 16px; }
.steps p { color: var(--ink-2); margin-top: 4px; }
.how-art .phone { width: min(320px, 100%); margin-inline: auto; }

/* ---------- 功能 ---------- */
.features { padding: 88px 0; }
.feat-list { list-style: none; padding: 0; margin: 36px 0 0; display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 0; border-top: 1px solid var(--line); }
.feat-list li { padding: 26px 22px 28px 0; border-bottom: 1px solid var(--line); }
.feat-list li:not(:nth-child(4n+1)) { padding-left: 22px; border-left: 1px solid var(--line); }
.feat-list h3 { display: flex; align-items: center; gap: 10px; }
.feat-list h3::before { content: ""; width: 8px; height: 8px; border-radius: 50%; background: var(--cobalt); flex: none; }
.feat-list p { margin-top: 8px; color: var(--ink-2); font-size: 15px; }

/* ---------- 场景 / 相关 ---------- */
.scenes, .related { padding: 80px 0; background: var(--ice); }
.scene-grid { margin-top: 32px; display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 16px; }
.scene-grid.three { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.scene { position: relative; display: block; background: #fff; border: 1px solid var(--line); border-radius: var(--radius); padding: 22px 22px 48px; color: var(--ink); transition: border-color .15s ease, transform .15s ease, box-shadow .15s ease; }
.scene:hover { text-decoration: none; border-color: var(--cobalt-l); transform: translateY(-2px); box-shadow: var(--shadow); }
.scene p { margin-top: 8px; color: var(--ink-2); font-size: 15px; }
.scene .arrow { position: absolute; left: 22px; bottom: 16px; color: var(--cobalt); font-weight: 800; }

/* ---------- 信任 ---------- */
.trust { padding: 88px 0; }
.trust-list { list-style: none; padding: 0; margin: 32px 0 0; display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 16px; }
.trust-list li { border-top: 3px solid var(--cobalt); padding-top: 16px; }
.trust-list p { margin-top: 6px; color: var(--ink-2); font-size: 15px; }
.legal-links { margin-top: 28px; font-size: 14px; color: var(--muted); }

/* ---------- FAQ ---------- */
.home-faq { padding: 80px 0; background: var(--ice); }
.faq { margin-top: 24px; display: grid; gap: 10px; }
.faq details { background: #fff; border: 1px solid var(--line); border-radius: 14px; }
.faq summary { cursor: pointer; list-style: none; padding: 16px 48px 16px 20px; font-weight: 700; position: relative; }
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after { content: "+"; position: absolute; right: 20px; top: 50%; transform: translateY(-50%); font-size: 22px; font-weight: 500; color: var(--cobalt); }
.faq details[open] summary::after { content: "−"; }
.faq details p { padding: 0 20px 18px; color: var(--ink-2); }
.more { margin-top: 20px; font-weight: 700; }

/* ---------- 下载 ---------- */
.download { padding: 88px 0; background: linear-gradient(180deg, #fff 0%, var(--ice) 100%); }
.dl-grid { margin-top: 32px; display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 24px; }
.dl-grid > div { background: #fff; border: 1px solid var(--line); border-radius: 22px; padding: 26px; }
.dl-grid h3 { margin-bottom: 16px; font-size: 20px; }
.dls { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 10px; }
.dl { position: relative; display: flex; flex-direction: column; padding: 11px 40px 11px 16px; border: 1px solid var(--line); border-radius: 14px; color: var(--ink); line-height: 1.3; }
.dl:hover { text-decoration: none; border-color: var(--cobalt); }
.dl-os { font-weight: 800; }
.dl-sub { font-size: 13px; color: var(--muted); }
.dl-ico { position: absolute; right: 14px; top: 50%; transform: translateY(-50%); color: var(--cobalt); font-weight: 800; }
.dl.is-suggested { border-color: var(--cobalt); background: var(--ice); }
.note { margin-top: 12px; font-size: 13.5px; color: var(--muted); }

/* ---------- 内容页 ---------- */
.doc-hero { background: linear-gradient(180deg, var(--ice) 0%, #fff 100%); padding: 48px 0 40px; border-bottom: 1px solid var(--line-2); }
.crumbs { display: flex; gap: 8px; font-size: 14px; color: var(--muted); }
.crumbs a { color: var(--muted); font-weight: 600; }
.doc-hero h1 { margin-top: 16px; font-size: clamp(32px, 5vw, 52px); font-weight: 900; letter-spacing: -.025em; max-width: 20em; }
.doc-hero .lead { font-size: 18px; max-width: 42em; }
.doc { display: grid; grid-template-columns: 220px minmax(0, 1fr); gap: 56px; padding: 48px 0 80px; }
.toc { position: sticky; top: 88px; align-self: start; font-size: 14px; }
.toc p { font-weight: 800; color: var(--ink); margin-bottom: 10px; }
.toc ol { list-style: none; margin: 0; padding: 0; border-left: 2px solid var(--line); }
.toc li a { display: block; padding: 5px 0 5px 14px; color: var(--muted); }
.toc li a:hover { color: var(--cobalt); text-decoration: none; }
.prose { max-width: 760px; font-size: 17px; color: var(--ink-2); }
.prose > * + * { margin-top: 16px; }
.prose h2 { margin-top: 48px; font-size: clamp(24px, 3vw, 30px); color: var(--ink); }
.prose h2:first-child { margin-top: 0; }
.prose strong { color: var(--ink); }
.prose a, .faq p a, .big a { text-decoration: underline; text-decoration-thickness: 1px; text-underline-offset: 3px; }
.prose ul, .prose ol:not(.steps) { padding-left: 1.3em; }
.prose li + li { margin-top: 8px; }
.prose .steps { margin-top: 20px; }
.prose .stores { max-width: 560px; }
.table { overflow-x: auto; border: 1px solid var(--line); border-radius: 14px; }
.table table { width: 100%; border-collapse: collapse; font-size: 15px; }
.table th, .table td { text-align: left; padding: 12px 16px; border-bottom: 1px solid var(--line-2); vertical-align: top; }
.table thead th { background: var(--ice); color: var(--ink); font-size: 14px; }
.table tbody th { color: var(--ink); font-weight: 700; white-space: nowrap; }
.table tr:last-child th, .table tr:last-child td { border-bottom: 0; }
.doc-shot .phone { width: min(260px, 70%); margin: 8px 0; }

/* ---------- 页脚 ---------- */
.footer { background: var(--ink); color: #c8d2e6; padding: 56px 0 28px; font-size: 14.5px; }
.footer a { color: #e8eefb; }
.footer .brand { color: #fff; }
.footer-top { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 2fr); gap: 48px; }
.footer-brand p { margin-top: 14px; max-width: 26em; }
.footer-cols { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 24px; }
.footer-cols h2 { font-size: 14px; color: #fff; letter-spacing: .02em; }
.footer-cols ul { list-style: none; margin: 12px 0 0; padding: 0; display: grid; gap: 8px; }
.footer-bottom { margin-top: 40px; padding-top: 20px; border-top: 1px solid rgba(255, 255, 255, .12); display: flex; flex-wrap: wrap; gap: 8px 24px; color: #9aa8c4; font-size: 13px; }
.footer-bottom a { color: #9aa8c4; }

/* ---------- 响应式 ---------- */
@media (max-width: 1080px) {
  .feat-list { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .feat-list li:not(:nth-child(4n+1)) { padding-left: 0; border-left: 0; }
  .feat-list li:nth-child(2n) { padding-left: 22px; border-left: 1px solid var(--line); }
  .scene-grid, .trust-list { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .footer-top { grid-template-columns: 1fr; }
}
@media (max-width: 920px) {
  .menu-btn { display: inline-grid; place-items: center; gap: 5px; width: 42px; height: 42px; margin-left: 4px; border: 1px solid var(--line); border-radius: 12px; background: #fff; cursor: pointer; }
  .menu-btn i { display: block; width: 18px; height: 2px; background: var(--ink); border-radius: 2px; }
  .nav { position: absolute; left: 0; right: 0; top: 64px; flex-direction: column; align-items: stretch; gap: 0; padding: 8px 20px 18px; background: #fff; border-bottom: 1px solid var(--line); box-shadow: 0 18px 30px -20px rgba(13, 26, 51, .3); display: none; }
  .nav.is-open { display: flex; }
  .nav > a { padding: 12px 0; border-bottom: 1px solid var(--line-2); }
  .langs { margin-top: 14px; align-self: flex-start; }
  .nav-cta { margin-left: auto; }
  .hero-in, .how-in, .doc { grid-template-columns: 1fr; }
  .hero-in { padding: 40px 0 48px; gap: 8px; }
  .hero-art { height: 440px; order: 2; }
  .phone-front { width: 230px; transform: translateX(-24%); }
  .phone-back { width: 190px; top: 50px; }
  .how-art { display: none; }
  .toc { position: static; border: 1px solid var(--line); border-radius: 14px; padding: 16px 18px; }
  .toc ol { columns: 2; column-gap: 20px; border-left: 0; }
  .toc li a { padding-left: 0; }
  .dl-grid { grid-template-columns: 1fr; }
}
@media (max-width: 640px) {
  .wrap, .narrow { width: calc(100% - 32px); }
  h2 { font-size: 28px; }
  .stores { grid-template-columns: 1fr 1fr; gap: 8px; }
  .store { padding: 9px 12px; min-height: 54px; }
  .store-name { font-size: 15px; }
  .store-sub { font-size: 11.5px; }
  .facts { grid-template-columns: 1fr 1fr; }
  .facts div:nth-child(3) { border-left: 0; }
  .facts div:nth-child(n+3) { border-top: 1px solid var(--line); }
  .feat-list { grid-template-columns: 1fr; }
  .feat-list li:nth-child(2n) { padding-left: 0; border-left: 0; }
  .feat-list li { padding-right: 0; }
  .scene-grid, .scene-grid.three, .trust-list { grid-template-columns: 1fr; }
  .what, .how, .features, .scenes, .related, .trust, .home-faq, .download { padding: 56px 0; }
  .hero-art { height: 380px; }
  .phone-front { width: 200px; border-radius: 24px; }
  .phone-back { width: 160px; border-radius: 22px; }
  .dls { grid-template-columns: 1fr; }
  .dl-grid > div { padding: 20px; }
  .footer-cols { grid-template-columns: 1fr 1fr; }
  .toc { display: none; }
  .doc { padding: 32px 0 56px; gap: 28px; }
  .prose { font-size: 16px; }
  .table tbody th { white-space: normal; }
  .nav-cta { display: none; }
  .menu-btn { margin-left: auto; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .store, .scene { transition: none; }
}