:root {
  --bs_ink: #071721;
  --bs_ink-2: #102a35;
  --bs_teal: #2de0b2;
  --bs_teal-dark: #087b66;
  --bs_blue: #6cb6ff;
  --bs_paper: #f4f7f6;
  --bs_white: #ffffff;
  --bs_line: #dbe5e2;
  --bs_muted: #60727a;
  --bs_warning: #ffce73;
  --bs_danger: #ff8c7e;
  --bs_radius: 20px;
  --bs_shadow: 0 20px 55px rgba(4, 30, 38, .10);
  --bs_width: 1180px;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 88px; }
body {
  margin: 0;
  color: var(--bs_ink);
  background: var(--bs_paper);
  font-family: "PingFang SC", "Microsoft YaHei", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 16px;
  line-height: 1.8;
  -webkit-font-smoothing: antialiased;
}
a { color: inherit; }
button, a { -webkit-tap-highlight-color: transparent; }
.bs_skip {
  position: fixed; left: 12px; top: -60px; z-index: 1000;
  padding: 10px 16px; border-radius: 10px;
  background: var(--bs_teal); color: var(--bs_ink); font-weight: 800;
}
.bs_skip:focus { top: 12px; }
.bs_wrap { width: min(calc(100% - 40px), var(--bs_width)); margin: 0 auto; }
.bs_kicker {
  margin: 0 0 12px; color: var(--bs_teal-dark);
  font-size: .84rem; font-weight: 800; letter-spacing: .08em;
}
.bs_section { padding: 88px 0; }
.bs_section-head {
  display: grid; grid-template-columns: minmax(0, 1fr) minmax(260px, 440px);
  gap: 48px; align-items: end; margin-bottom: 40px;
}
.bs_section h2 {
  max-width: 780px; margin: 0;
  font-size: clamp(1.8rem, 3.6vw, 2.9rem); line-height: 1.2; letter-spacing: -.03em;
}
.bs_section-head > p { margin: 0; color: var(--bs_muted); }
.bs_prose { max-width: 780px; color: #3b5057; }
.bs_prose p { margin: 0 0 16px; }
.bs_prose p:last-child { margin-bottom: 0; }
.bs_notice { background: #031017; color: #d9e9e6; font-size: .8rem; text-align: center; }
.bs_notice .bs_wrap { padding: 7px 0; }
.bs_header {
  position: sticky; top: 0; z-index: 50;
  border-bottom: 1px solid rgba(255,255,255,.12);
  background: rgba(7, 23, 33, .92); color: var(--bs_white); backdrop-filter: blur(14px);
}
.bs_nav { min-height: 68px; display: flex; align-items: center; justify-content: space-between; gap: 28px; }
.bs_logo {
  display: inline-flex; align-items: center; gap: 11px;
  color: var(--bs_white); text-decoration: none; font-size: 1.04rem; font-weight: 900; letter-spacing: -.02em;
}
.bs_logo-mark {
  width: 34px; height: 34px; display: grid; place-items: center;
  border: 1px solid rgba(45, 224, 178, .58); border-radius: 10px;
  background: rgba(45, 224, 178, .10); color: var(--bs_teal);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-weight: 900;
}
.bs_logo small { color: #91aaa9; font-size: .72rem; font-weight: 600; letter-spacing: .04em; }
.bs_nav-links { display: flex; align-items: center; gap: 26px; }
.bs_nav-links a { color: #c6d5d3; text-decoration: none; font-size: .9rem; font-weight: 650; }
.bs_nav-links a:hover, .bs_nav-links a:focus-visible { color: var(--bs_teal); }
.bs_nav-cta { padding: 9px 16px; border: 1px solid rgba(45, 224, 178, .62); border-radius: 999px; color: var(--bs_teal) !important; }
.bs_hero {
  position: relative; overflow: hidden; padding: 74px 0 80px;
  background:
    linear-gradient(rgba(45,224,178,.045) 1px, transparent 1px),
    linear-gradient(90deg, rgba(45,224,178,.045) 1px, transparent 1px),
    radial-gradient(circle at 72% 26%, rgba(45,224,178,.16), transparent 27%),
    var(--bs_ink);
  background-size: 42px 42px, 42px 42px, auto, auto;
  color: var(--bs_white);
}
.bs_hero::after {
  content: ""; position: absolute; right: -110px; bottom: -180px; width: 460px; height: 460px;
  border: 1px solid rgba(108,182,255,.16); border-radius: 50%;
  box-shadow: 0 0 0 70px rgba(108,182,255,.025), 0 0 0 140px rgba(108,182,255,.018);
  pointer-events: none;
}
.bs_hero-grid {
  position: relative; z-index: 1; display: grid;
  grid-template-columns: minmax(0, 1.18fr) minmax(340px, .82fr); gap: 72px; align-items: center;
}
.bs_hero .bs_kicker { color: var(--bs_teal); }
.bs_hero h1 {
  max-width: 760px; margin: 0 0 22px;
  font-size: clamp(2.4rem, 5.4vw, 4.8rem); line-height: 1.04; letter-spacing: -.05em;
}
.bs_hero h1 em { display: block; color: var(--bs_teal); font-family: Georgia, "Times New Roman", serif; font-weight: 500; }
.bs_hero-lead { max-width: 700px; margin: 0; color: #bcd0cf; font-size: 1.06rem; line-height: 1.9; }
.bs_hero-actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 31px; }
.bs_btn {
  min-height: 50px; display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 11px 21px; border: 1px solid transparent; border-radius: 999px;
  text-decoration: none; font-weight: 800;
  transition: transform .2s ease, background-color .2s ease, border-color .2s ease;
}
.bs_btn:hover { transform: translateY(-2px); }
.bs_btn-primary { background: var(--bs_teal); color: #03231b; box-shadow: 0 12px 32px rgba(45,224,178,.20); }
.bs_btn-secondary { border-color: rgba(255,255,255,.24); background: rgba(255,255,255,.04); color: var(--bs_white); }
.bs_byline {
  display: flex; flex-wrap: wrap; align-items: center; gap: 10px 22px;
  margin-top: 30px; color: #9db3b1; font-size: .82rem;
}
.bs_byline b { color: #d9e9e6; font-weight: 700; }
.bs_brief {
  position: relative; overflow: hidden;
  border: 1px solid rgba(255,255,255,.16); border-radius: 26px;
  background: rgba(255,255,255,.065); box-shadow: 0 28px 65px rgba(0,0,0,.28); backdrop-filter: blur(12px);
}
.bs_brief-top {
  display: flex; align-items: center; justify-content: space-between;
  padding: 18px 20px; border-bottom: 1px solid rgba(255,255,255,.11);
}
.bs_brief-top strong { font-size: .94rem; }
.bs_brief-top span { color: #a4bbb8; font-size: .72rem; }
.bs_brief-body { padding: 20px; }
.bs_brief-row {
  display: grid; grid-template-columns: 34px 1fr; gap: 13px;
  padding: 15px 0; border-top: 1px solid rgba(255,255,255,.10);
}
.bs_brief-row:first-of-type { border-top: 0; padding-top: 0; }
.bs_brief-num {
  width: 30px; height: 30px; display: grid; place-items: center; border-radius: 50%;
  background: rgba(45,224,178,.13); color: var(--bs_teal);
  font: 800 .75rem/1 ui-monospace, SFMono-Regular, Menlo, monospace;
}
.bs_brief-row strong { display: block; font-size: .94rem; }
.bs_brief-row p { margin: 2px 0 0; color: #9db3b1; font-size: .8rem; line-height: 1.6; }
.bs_brief-foot { padding: 13px 20px; background: rgba(255,206,115,.09); color: #dac597; font-size: .76rem; }
.bs_answer { padding: 0 0 88px; margin-top: -1px; background: linear-gradient(to bottom, var(--bs_ink) 0 40px, var(--bs_paper) 40px); }
.bs_answer-card {
  position: relative; z-index: 2; display: grid; grid-template-columns: 190px 1fr; gap: 36px;
  padding: 35px 42px; border: 1px solid var(--bs_line); border-radius: var(--bs_radius);
  background: var(--bs_white); box-shadow: var(--bs_shadow);
}
.bs_answer-label { color: var(--bs_teal-dark); font-size: .9rem; font-weight: 900; letter-spacing: .04em; }
.bs_answer-text { margin: 0; font-size: clamp(1.02rem, 2vw, 1.25rem); font-weight: 600; line-height: 1.8; }
.bs_answer-text strong { color: var(--bs_teal-dark); }
.bs_answer-text small { display: block; margin-top: 12px; color: var(--bs_muted); font-size: .88rem; font-weight: 500; }
.bs_steps { display: grid; grid-template-columns: repeat(4, 1fr); border-top: 1px solid var(--bs_line); border-bottom: 1px solid var(--bs_line); }
.bs_step { position: relative; padding: 34px 30px 32px 0; }
.bs_step:not(:last-child)::after { content: ""; position: absolute; top: 34px; right: 22px; width: 44px; height: 1px; background: var(--bs_line); }
.bs_step-num { display: block; margin-bottom: 27px; color: var(--bs_teal-dark); font: 800 .78rem/1 ui-monospace, SFMono-Regular, Menlo, monospace; }
.bs_step h3 { margin: 0 0 9px; font-size: 1.08rem; line-height: 1.4; }
.bs_step p { margin: 0; color: var(--bs_muted); font-size: .9rem; line-height: 1.75; }
.bs_compare { background: var(--bs_white); }
.bs_table-wrap { overflow-x: auto; border: 1px solid var(--bs_line); border-radius: var(--bs_radius); box-shadow: 0 16px 40px rgba(7,23,33,.06); }
.bs_table { width: 100%; min-width: 720px; border-collapse: collapse; background: var(--bs_white); }
.bs_table th, .bs_table td { padding: 21px 24px; border-bottom: 1px solid var(--bs_line); text-align: left; vertical-align: top; }
.bs_table tr:last-child th, .bs_table tr:last-child td { border-bottom: 0; }
.bs_table thead th { background: #0a2029; color: var(--bs_white); font-size: .86rem; }
.bs_table thead th:first-child { color: #8eaaa8; }
.bs_table tbody th { width: 21%; color: #31484f; font-size: .88rem; }
.bs_table td { width: 39.5%; color: #52676e; font-size: .9rem; }
.bs_table td strong { display: block; margin-bottom: 3px; color: var(--bs_ink); font-size: .98rem; }
.bs_table .bs_highlight { background: #f0fbf7; }
.bs_example {
  margin-top: 28px; padding: 24px 28px;
  border-left: 3px solid var(--bs_teal); border-radius: 0 16px 16px 0;
  background: #f4fbf8; color: #34494f; font-size: .94rem;
}
.bs_example strong { color: var(--bs_ink); }
.bs_example p { margin: 0 0 10px; }
.bs_example p:last-child { margin: 0; }
.bs_routes-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.bs_route {
  min-height: 310px; display: flex; flex-direction: column; padding: 28px;
  border: 1px solid var(--bs_line); border-radius: var(--bs_radius);
  background: var(--bs_white); box-shadow: 0 12px 35px rgba(7,23,33,.045);
}
.bs_route:nth-child(2) { transform: translateY(18px); }
.bs_route-tag {
  align-self: flex-start; margin-bottom: 30px; padding: 5px 10px; border-radius: 999px;
  background: #e4f8f2; color: var(--bs_teal-dark); font-size: .72rem; font-weight: 850;
}
.bs_route h3 { margin: 0 0 12px; font-size: 1.22rem; line-height: 1.35; }
.bs_route p { margin: 0; color: var(--bs_muted); font-size: .91rem; }
.bs_route-note { margin-top: auto !important; padding-top: 22px; color: #40555d !important; font-size: .78rem !important; font-weight: 700; }
.bs_route-note::before { content: ""; display: inline-block; width: 18px; height: 2px; margin: 0 8px 4px 0; background: var(--bs_teal); }
.bs_mechanics { padding-bottom: 96px; }
.bs_mechanics-grid { display: grid; grid-template-columns: minmax(280px, .72fr) minmax(0, 1.28fr); gap: 44px; align-items: start; }
.bs_mechanics-intro { position: sticky; top: 104px; }
.bs_mechanics-intro h2 { font-size: clamp(1.9rem, 3.6vw, 3rem); }
.bs_mechanics-intro > p:last-child { color: var(--bs_muted); }
.bs_fact-list { display: grid; gap: 12px; }
.bs_fact {
  display: grid; grid-template-columns: 64px 1fr; gap: 18px; align-items: start;
  padding: 25px 27px; border: 1px solid var(--bs_line); border-radius: 16px; background: rgba(255,255,255,.78);
}
.bs_fact-code { padding-top: 5px; color: var(--bs_teal-dark); font: 800 .8rem/1 ui-monospace, SFMono-Regular, Menlo, monospace; }
.bs_fact h3 { margin: 0 0 5px; font-size: 1.03rem; }
.bs_fact p { margin: 0; color: var(--bs_muted); font-size: .89rem; }
.bs_checklist { background: #dff5ee; }
.bs_check-grid { display: grid; grid-template-columns: minmax(0, .92fr) minmax(0, 1.08fr); gap: 50px; align-items: start; }
.bs_check-intro h2 { margin: 0 0 20px; font-size: clamp(1.9rem, 4vw, 3.2rem); line-height: 1.1; letter-spacing: -.04em; }
.bs_check-intro p { color: #45635f; }
.bs_check-items { counter-reset: checklist; display: grid; gap: 0; border-top: 1px solid rgba(7,23,33,.16); }
.bs_check-item { counter-increment: checklist; display: grid; grid-template-columns: 48px 1fr; gap: 20px; padding: 20px 0; border-bottom: 1px solid rgba(7,23,33,.16); }
.bs_check-item::before { content: counter(checklist) "."; padding-top: 4px; color: var(--bs_teal-dark); font: 800 .9rem/1 ui-monospace, SFMono-Regular, Menlo, monospace; }
.bs_check-item h3 { margin: 0 0 4px; font-size: 1rem; }
.bs_check-item p { margin: 0; color: #4d6965; font-size: .88rem; }
.bs_risk { background: var(--bs_ink); color: var(--bs_white); }
.bs_risk .bs_kicker { color: var(--bs_warning); }
.bs_risk .bs_section-head > p { color: #9db3b1; }
.bs_risk-grid { display: grid; grid-template-columns: repeat(2, 1fr); border-top: 1px solid rgba(255,255,255,.14); border-left: 1px solid rgba(255,255,255,.14); }
.bs_risk-item { min-height: 210px; padding: 30px; border-right: 1px solid rgba(255,255,255,.14); border-bottom: 1px solid rgba(255,255,255,.14); }
.bs_risk-icon { display: block; margin-bottom: 30px; color: var(--bs_warning); font-size: .8rem; font-weight: 800; letter-spacing: .06em; }
.bs_risk-item h3 { margin: 0 0 8px; font-size: 1.08rem; }
.bs_risk-item p { margin: 0; color: #9db3b1; font-size: .89rem; }
.bs_risk-note { margin: 28px 0 0; padding: 17px 20px; border-left: 3px solid var(--bs_warning); background: rgba(255,206,115,.08); color: #dacaa9; font-size: .86rem; }
.bs_faq-list { display: grid; grid-template-columns: repeat(2, 1fr); gap: 14px; align-items: start; }
.bs_faq details { border: 1px solid var(--bs_line); border-radius: 14px; background: var(--bs_white); }
.bs_faq summary { position: relative; padding: 20px 54px 20px 21px; cursor: pointer; list-style: none; font-weight: 800; line-height: 1.45; }
.bs_faq summary::-webkit-details-marker { display: none; }
.bs_faq summary::after { content: "+"; position: absolute; right: 20px; top: 50%; transform: translateY(-50%); color: var(--bs_teal-dark); font: 500 1.45rem/1 Arial, sans-serif; }
.bs_faq details[open] summary::after { content: "−"; }
.bs_faq details[open] summary { border-bottom: 1px solid var(--bs_line); }
.bs_faq-answer { padding: 17px 21px 20px; color: var(--bs_muted); font-size: .91rem; }
.bs_faq-answer p { margin: 0 0 10px; }
.bs_faq-answer p:last-child { margin: 0; }
.bs_final { padding: 0 0 88px; }
.bs_final-card {
  position: relative; overflow: hidden; display: grid; grid-template-columns: minmax(0, 1fr) auto;
  gap: 38px; align-items: center; padding: 48px; border-radius: 24px;
  background: var(--bs_ink); color: var(--bs_white); box-shadow: var(--bs_shadow);
}
.bs_final-card::before { content: "B"; position: absolute; right: 20%; top: -84px; color: rgba(45,224,178,.06); font: 900 280px/1 Arial, sans-serif; pointer-events: none; }
.bs_final h2 { position: relative; margin: 0 0 8px; font-size: clamp(1.6rem, 2.8vw, 2.3rem); line-height: 1.2; letter-spacing: -.03em; }
.bs_final p { position: relative; margin: 0; color: #9db3b1; font-size: .92rem; }
.bs_footer { padding: 42px 0 100px; border-top: 1px solid var(--bs_line); background: #edf2f0; color: #5a6f75; font-size: .8rem; }
.bs_footer-grid { display: grid; grid-template-columns: .75fr 1.25fr; gap: 48px; }
.bs_footer strong { display: block; margin-bottom: 10px; color: var(--bs_ink); font-size: .86rem; }
.bs_footer p, .bs_footer ul { margin: 0; }
.bs_footer ul { padding-left: 1.15rem; }
.bs_footer-bottom { display: flex; justify-content: space-between; gap: 24px; margin-top: 30px; padding-top: 22px; border-top: 1px solid var(--bs_line); }
.bs_mobile-bar {
  position: fixed; left: 12px; right: 12px; bottom: calc(10px + env(safe-area-inset-bottom)); z-index: 60;
  display: none; align-items: center; justify-content: space-between; gap: 14px;
  padding: 10px 10px 10px 15px; border: 1px solid rgba(255,255,255,.14); border-radius: 16px;
  background: rgba(7,23,33,.95); box-shadow: 0 16px 42px rgba(0,0,0,.28); color: var(--bs_white); backdrop-filter: blur(14px);
}
.bs_mobile-bar span { font-size: .78rem; font-weight: 800; line-height: 1.35; }
.bs_mobile-bar .bs_btn { min-height: 42px; padding: 8px 15px; font-size: .8rem; white-space: nowrap; }
@media (max-width: 900px) {
  .bs_nav-links a:not(.bs_nav-cta) { display: none; }
  .bs_hero-grid, .bs_section-head, .bs_mechanics-grid, .bs_check-grid, .bs_final-card, .bs_footer-grid { grid-template-columns: 1fr; }
  .bs_hero-grid { gap: 46px; }
  .bs_section-head { gap: 18px; }
  .bs_steps { grid-template-columns: repeat(2, 1fr); }
  .bs_step:nth-child(2)::after { display: none; }
  .bs_routes-grid { grid-template-columns: 1fr; }
  .bs_route { min-height: 0; }
  .bs_route:nth-child(2) { transform: none; }
  .bs_mechanics-intro { position: static; }
  .bs_final-card { align-items: start; }
  .bs_final-card .bs_btn { justify-self: start; }
}
@media (max-width: 640px) {
  .bs_wrap { width: min(calc(100% - 28px), var(--bs_width)); }
  .bs_notice { text-align: left; }
  .bs_nav { min-height: 62px; }
  .bs_logo small { display: none; }
  .bs_nav-cta { padding: 7px 12px; font-size: .78rem !important; }
  .bs_hero { padding: 56px 0 64px; }
  .bs_hero h1 { font-size: clamp(2.2rem, 11vw, 3.4rem); }
  .bs_hero-actions { display: grid; grid-template-columns: 1fr; }
  .bs_btn { width: 100%; }
  .bs_brief { border-radius: 20px; }
  .bs_answer { padding-bottom: 64px; }
  .bs_answer-card { grid-template-columns: 1fr; gap: 12px; padding: 26px 23px; }
  .bs_section { padding: 64px 0; }
  .bs_steps { grid-template-columns: 1fr; }
  .bs_step { display: grid; grid-template-columns: 44px 1fr; gap: 0 12px; padding: 23px 0; border-bottom: 1px solid var(--bs_line); }
  .bs_step::after { display: none !important; }
  .bs_step-num { grid-row: 1 / span 2; margin: 5px 0 0; }
  .bs_step h3 { margin-top: 0; }
  .bs_route { padding: 24px; }
  .bs_route-tag { margin-bottom: 22px; }
  .bs_fact { grid-template-columns: 50px 1fr; padding: 21px; }
  .bs_example { padding: 20px; }
  .bs_risk-grid, .bs_faq-list { grid-template-columns: 1fr; }
  .bs_risk-item { min-height: 0; padding: 25px 23px; }
  .bs_risk-icon { margin-bottom: 20px; }
  .bs_final-card { padding: 32px 25px; }
  .bs_final-card .bs_btn { width: 100%; }
  .bs_footer-bottom { display: block; }
  .bs_footer-bottom span { display: block; margin-bottom: 6px; }
  .bs_mobile-bar { display: flex; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition-duration: .01ms !important; }
}