:root {
  --red: #e11b22;
  --red-dark: #b81016;
  --charcoal: #171717;
  --charcoal-2: #242424;
  --paper: #ffffff;
  --off-white: #f7f4ef;
  --soft: #f2f2f2;
  --ink: #292929;
  --muted: #686868;
  --line: #dedede;
  --white: #ffffff;
  --shell: 1180px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 84px;
}

body {
  margin: 0;
  min-width: 320px;
  color: var(--ink);
  background: var(--paper);
  font-family: Arial, "Microsoft YaHei", "PingFang SC", "Segoe UI", sans-serif;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

img {
  display: block;
  max-width: 100%;
}

a {
  color: inherit;
  text-decoration: none;
}

button,
a {
  -webkit-tap-highlight-color: transparent;
}

button {
  font: inherit;
}

.skip-link {
  position: fixed;
  top: -90px;
  left: 18px;
  z-index: 1000;
  padding: 10px 15px;
  color: var(--charcoal);
  background: var(--white);
  font-weight: 850;
}

.skip-link:focus {
  top: 18px;
}

.header-shell,
.hero,
.section,
.final-section,
.footer-shell {
  width: min(calc(100% - 40px), var(--shell));
  margin-inline: auto;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  color: var(--white);
  background: rgba(23, 23, 23, 0.98);
  border-bottom: 1px solid #303030;
  backdrop-filter: blur(14px);
}

.header-shell {
  min-height: 78px;
  display: grid;
  grid-template-columns: 230px 1fr 160px;
  gap: 28px;
  align-items: center;
}

.brand {
  width: max-content;
}

.brand-plate,
.footer-logo-plate {
  min-width: 190px;
  min-height: 48px;
  display: inline-flex;
  align-items: center;
  padding: 6px 12px;
  background: #0d0d0d;
  border: 1px solid #353535;
}

.brand img,
.footer-brand img {
  width: auto;
  height: 34px;
  object-fit: contain;
}

.site-nav {
  display: flex;
  justify-content: center;
  gap: 30px;
  color: #c0c0c0;
  font-size: 13px;
  font-weight: 750;
}

.site-nav a {
  padding: 25px 0 23px;
}

.site-nav a:hover,
.site-nav a:focus-visible {
  color: var(--white);
}

.header-download {
  justify-self: end;
  padding: 11px 14px;
  color: var(--white);
  background: var(--red);
  text-align: center;
  font-size: 13px;
  font-weight: 850;
}

.header-download:hover,
.header-download:focus-visible {
  background: var(--red-dark);
}

.menu-button {
  display: none;
  width: 44px;
  height: 44px;
  background: transparent;
  border: 1px solid #444;
}

.menu-button span {
  display: block;
  width: 19px;
  height: 2px;
  margin: 4px auto;
  background: var(--white);
}

.hero {
  position: relative;
  min-height: 670px;
  display: grid;
  grid-template-columns: 0.92fr 1.08fr;
  gap: 60px;
  align-items: center;
  padding-top: 82px;
  padding-bottom: 82px;
  overflow: hidden;
  background: var(--off-white);
}

.hero::before {
  content: "";
  position: absolute;
  inset: 0 auto 0 calc(50% + 80px);
  width: 100vw;
  background: var(--charcoal);
  z-index: 0;
}

.hero-number {
  position: absolute;
  left: 0;
  top: 44px;
  color: rgba(225, 27, 34, 0.08);
  font-size: 220px;
  font-weight: 950;
  line-height: 1;
  letter-spacing: -0.08em;
  pointer-events: none;
}

.hero-copy,
.hero-visual {
  position: relative;
  z-index: 2;
}

.eyebrow,
.section-label {
  margin: 0 0 15px;
  color: var(--red);
  font-size: 10px;
  font-weight: 900;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

.hero h1 {
  margin: 0;
  color: var(--charcoal);
  font-size: clamp(52px, 6.8vw, 88px);
  line-height: 1;
  letter-spacing: -0.055em;
}

.hero-lead {
  max-width: 650px;
  margin: 29px 0 0;
  color: #555;
  font-size: 18px;
  line-height: 1.9;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 13px;
  margin-top: 34px;
}

.primary-button,
.secondary-button {
  min-height: 56px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 22px;
  padding: 13px 20px;
  border: 1px solid transparent;
  font-weight: 850;
}

.primary-button {
  min-width: 250px;
  color: var(--white);
  background: var(--red);
}

.primary-button:hover,
.primary-button:focus-visible {
  background: var(--red-dark);
}

.primary-button b {
  font-size: 20px;
}

.secondary-button {
  color: var(--charcoal);
  background: var(--white);
  border-color: var(--line);
}

.hero-answer {
  display: grid;
  grid-template-columns: 145px 1fr;
  gap: 20px;
  margin-top: 37px;
  padding-top: 22px;
  border-top: 1px solid #d2ccc5;
}

.hero-answer strong {
  color: var(--red);
  font-size: 12px;
}

.hero-answer p {
  margin: 0;
  color: #666;
  font-size: 14px;
}

.hero-visual {
  padding: 30px 20px;
  color: var(--white);
}

.visual-label {
  display: flex;
  gap: 10px;
  margin-bottom: 20px;
}

.visual-label span {
  padding: 6px 9px;
  color: #bbb;
  border: 1px solid #3b3b3b;
  font-size: 9px;
  font-weight: 850;
}

.hero-visual img {
  width: 100%;
  max-height: 440px;
  object-fit: contain;
}

.section {
  padding-top: 98px;
  padding-bottom: 98px;
}

.direct-section {
  display: grid;
  grid-template-columns: 0.6fr 1.4fr;
  gap: 75px;
  align-items: end;
  background: var(--paper);
}

.direct-intro h2,
.section-heading h2,
.difference-copy h2,
.install-heading h2,
.source-title h2,
.trouble-heading h2,
.faq-heading h2,
.related-heading h2,
.final-copy h2 {
  margin: 0;
  color: var(--charcoal);
  font-size: clamp(32px, 4.2vw, 51px);
  line-height: 1.17;
  letter-spacing: -0.04em;
}

.direct-intro > p:not(.section-label),
.section-heading > p:not(.section-label),
.trouble-heading > p:not(.section-label),
.faq-heading > p:not(.section-label) {
  margin: 20px 0 0;
  color: var(--muted);
}

.direct-action {
  min-height: 165px;
  display: grid;
  grid-template-columns: 70px 1fr 1px 1fr 180px;
  gap: 25px;
  align-items: center;
  padding: 25px;
  color: var(--white);
  background: var(--charcoal);
}

.action-index {
  color: var(--red);
  font-size: 34px;
  font-weight: 950;
}

.direct-action strong,
.direct-action span {
  display: block;
}

.direct-action strong {
  font-size: 15px;
}

.direct-action span {
  color: #a9a9a9;
  font-size: 11px;
}

.action-divider {
  height: 65px;
  background: #3a3a3a;
}

.direct-action a {
  padding: 12px 15px;
  color: var(--white);
  background: var(--red);
  text-align: center;
  font-size: 12px;
  font-weight: 850;
}

.choose-section {
  background: var(--soft);
}

.section-heading {
  max-width: 850px;
}

.route-list {
  margin-top: 44px;
  border-top: 2px solid var(--charcoal);
}

.route-list article {
  display: grid;
  grid-template-columns: 70px 1fr 300px;
  gap: 26px;
  align-items: center;
  min-height: 155px;
  padding: 24px 0;
  border-bottom: 1px solid var(--line);
}

.route-code {
  width: 56px;
  height: 56px;
  display: grid;
  place-items: center;
  color: var(--white);
  background: var(--charcoal);
  font-size: 20px;
  font-weight: 900;
}

.route-list article:nth-child(2) .route-code {
  background: var(--red);
}

.route-copy > span {
  color: var(--red);
  font-size: 9px;
  font-weight: 900;
  letter-spacing: 0.1em;
}

.route-copy h3 {
  margin: 5px 0 7px;
  color: var(--charcoal);
  font-size: 20px;
}

.route-copy p {
  margin: 0;
  color: var(--muted);
}

.route-check {
  padding-left: 23px;
  border-left: 1px solid var(--line);
}

.route-check b,
.route-check span {
  display: block;
}

.route-check b {
  color: var(--charcoal);
  font-size: 11px;
}

.route-check span {
  margin-top: 5px;
  color: var(--muted);
  font-size: 11px;
}

.difference-section {
  display: grid;
  grid-template-columns: 1fr 0.85fr;
  gap: 65px;
  align-items: center;
  background: var(--paper);
}

.difference-lead {
  margin: 23px 0 0;
  color: var(--charcoal);
  font-size: 20px;
  font-weight: 700;
  line-height: 1.7;
}

.difference-points {
  margin-top: 31px;
  border-top: 2px solid var(--charcoal);
}

.difference-points article {
  display: grid;
  grid-template-columns: 95px 1fr;
  gap: 20px;
  padding: 19px 0;
  border-bottom: 1px solid var(--line);
}

.difference-points b {
  color: var(--red);
  font-size: 12px;
}

.difference-points p {
  margin: 0;
  color: var(--muted);
}

.difference-visual {
  margin: 0;
  padding: 20px;
  background: var(--charcoal);
}

.difference-visual img {
  width: 100%;
  max-height: 430px;
  object-fit: contain;
}

.difference-visual figcaption {
  margin-top: 12px;
  color: #888;
  font-size: 10px;
}

.install-section {
  display: grid;
  grid-template-columns: 0.52fr 1.48fr;
  gap: 70px;
  color: var(--white);
  background: var(--charcoal);
}

.install-heading h2 {
  color: var(--white);
}

.install-steps {
  margin: 0;
  padding: 0;
  list-style: none;
}

.install-steps li {
  display: grid;
  grid-template-columns: 85px 1fr;
  gap: 24px;
  min-height: 155px;
  padding: 24px 0;
  border-top: 1px solid #383838;
}

.install-steps li:last-child {
  border-bottom: 1px solid #383838;
}

.step-number {
  color: var(--red);
  font-size: 32px;
  font-weight: 950;
}

.install-steps span {
  color: var(--red);
  font-size: 9px;
  font-weight: 900;
  letter-spacing: 0.1em;
}

.install-steps h3 {
  margin: 5px 0 8px;
  font-size: 19px;
}

.install-steps p {
  margin: 0;
  color: #aaa;
}

.install-callout {
  grid-column: 2;
  display: grid;
  grid-template-columns: 190px 1fr 135px;
  gap: 22px;
  align-items: center;
  padding: 22px 24px;
  color: var(--charcoal);
  background: var(--white);
}

.install-callout strong {
  font-size: 14px;
}

.install-callout p {
  margin: 0;
  color: #666;
  font-size: 12px;
}

.install-callout a {
  padding: 11px 15px;
  color: var(--white);
  background: var(--red);
  text-align: center;
  font-size: 12px;
  font-weight: 850;
}

.source-section {
  display: grid;
  grid-template-columns: 0.56fr 1.44fr;
  gap: 72px;
  background: var(--off-white);
}

.source-list {
  border-top: 2px solid var(--charcoal);
}

.source-list article {
  display: grid;
  grid-template-columns: 45px 1fr;
  gap: 18px;
  padding: 23px 0;
  border-bottom: 1px solid #d7d0c8;
}

.source-list > article > b {
  color: var(--red);
  font-size: 11px;
}

.source-list h3 {
  margin: -4px 0 7px;
  color: var(--charcoal);
  font-size: 18px;
}

.source-list p {
  margin: 0;
  color: var(--muted);
}

.trouble-section {
  background: var(--paper);
}

.trouble-heading {
  display: grid;
  grid-template-columns: 1fr 0.7fr;
  gap: 70px;
  align-items: end;
}

.trouble-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  margin-top: 43px;
  border-top: 1px solid var(--line);
  border-left: 1px solid var(--line);
}

.trouble-grid article {
  min-height: 220px;
  padding: 26px;
  border-right: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.trouble-grid article:nth-child(2),
.trouble-grid article:nth-child(4),
.trouble-grid article:nth-child(6) {
  background: var(--soft);
}

.trouble-grid span {
  color: var(--red);
  font-size: 10px;
  font-weight: 900;
}

.trouble-grid h3 {
  margin: 26px 0 9px;
  color: var(--charcoal);
  font-size: 18px;
}

.trouble-grid p {
  margin: 0;
  color: var(--muted);
  font-size: 13px;
}

.faq-section {
  display: grid;
  grid-template-columns: 0.6fr 1.4fr;
  gap: 75px;
  background: var(--off-white);
}

.faq-heading {
  position: sticky;
  top: 112px;
  align-self: start;
}

.faq-list {
  border-top: 2px solid var(--charcoal);
}

.faq-list details {
  border-bottom: 1px solid #d7d0c8;
}

.faq-list summary {
  position: relative;
  padding: 24px 55px 24px 0;
  color: var(--charcoal);
  font-size: 16px;
  font-weight: 850;
  cursor: pointer;
  list-style: none;
}

.faq-list summary::-webkit-details-marker {
  display: none;
}

.faq-list summary span {
  position: absolute;
  right: 4px;
  top: 20px;
  width: 30px;
  height: 30px;
  display: grid;
  place-items: center;
  color: var(--red);
  border: 1px solid #cfc5bc;
  border-radius: 50%;
  transition: transform 0.2s ease;
}

.faq-list details[open] summary span {
  transform: rotate(45deg);
}

.faq-list details p {
  margin: -2px 0 23px;
  color: var(--muted);
}

.related-section {
  display: grid;
  grid-template-columns: 0.52fr 1.48fr;
  gap: 70px;
  background: var(--paper);
}

.related-links {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  border-top: 1px solid var(--line);
  border-left: 1px solid var(--line);
}

.related-links a {
  min-height: 128px;
  display: grid;
  align-content: center;
  padding: 22px;
  border-right: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.related-links a:last-child {
  grid-column: 1 / -1;
}

.related-links a:hover,
.related-links a:focus-visible {
  background: var(--soft);
}

.related-links strong {
  color: var(--red);
  font-size: 15px;
}

.related-links span {
  margin-top: 5px;
  color: var(--muted);
  font-size: 11px;
}

.final-section {
  min-height: 265px;
  display: grid;
  grid-template-columns: 120px 1fr 250px;
  gap: 40px;
  align-items: center;
  margin-bottom: 90px;
  padding: 42px 48px;
  color: var(--white);
  background: var(--red);
}

.final-index {
  color: var(--white);
  font-size: 76px;
  font-weight: 950;
  line-height: 1;
  opacity: 0.3;
}

.final-copy p {
  margin: 0 0 9px;
  color: #ffd0d2;
  font-size: 9px;
  font-weight: 900;
  letter-spacing: 0.14em;
}

.final-copy h2 {
  color: var(--white);
  font-size: clamp(28px, 3.6vw, 43px);
}

.final-copy span {
  display: block;
  margin-top: 13px;
  color: #ffe0e1;
  font-size: 11px;
}

.final-button {
  min-height: 68px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 18px;
  padding: 16px 20px;
  color: var(--charcoal);
  background: var(--white);
  font-weight: 900;
}

.final-button b {
  font-size: 20px;
}

.site-footer {
  padding: 52px 0 32px;
  color: #aaa;
  background: var(--charcoal);
}

.footer-shell {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 32px 55px;
}

.footer-brand p {
  max-width: 710px;
  margin: 17px 0 0;
  color: #777;
  font-size: 11px;
}

.footer-nav {
  display: grid;
  grid-template-columns: repeat(2, auto);
  gap: 8px 25px;
  font-size: 12px;
  font-weight: 700;
}

.footer-nav a:hover,
.footer-nav a:focus-visible {
  color: var(--white);
}

.copyright {
  grid-column: 1 / -1;
  margin: 5px 0 0;
  padding-top: 21px;
  color: #555;
  border-top: 1px solid #303030;
  font-size: 11px;
}

.mobile-download {
  display: none;
}

@media (max-width: 930px) {
  .header-shell {
    grid-template-columns: 210px 1fr 150px;
  }

  .site-nav {
    gap: 18px;
  }

  .hero {
    gap: 35px;
  }

  .direct-section,
  .difference-section,
  .install-section,
  .source-section,
  .faq-section,
  .related-section {
    gap: 45px;
  }

  .direct-action {
    grid-template-columns: 60px 1fr 1px 1fr;
  }

  .direct-action a {
    grid-column: 2 / -1;
  }

  .trouble-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 800px) {
  html {
    scroll-padding-top: 72px;
  }

  .header-shell {
    min-height: 70px;
    grid-template-columns: 1fr auto;
  }

  .header-download {
    display: none;
  }

  .menu-button {
    display: block;
  }

  .site-nav {
    position: absolute;
    left: 20px;
    right: 20px;
    top: calc(100% + 8px);
    display: none;
    padding: 9px;
    background: var(--charcoal);
    border: 1px solid #3a3a3a;
    box-shadow: 0 20px 50px rgba(0, 0, 0, 0.25);
  }

  .site-nav.is-open {
    display: grid;
  }

  .site-nav a {
    padding: 11px 12px;
  }

  .hero {
    grid-template-columns: 1fr;
  }

  .hero::before {
    inset: 52% -50vw 0;
  }

  .hero-copy {
    text-align: center;
  }

  .hero-actions {
    justify-content: center;
  }

  .hero-answer {
    max-width: 700px;
    margin-inline: auto;
    text-align: left;
  }

  .direct-section,
  .difference-section,
  .install-section,
  .source-section,
  .faq-section,
  .related-section {
    grid-template-columns: 1fr;
  }

  .route-list article {
    grid-template-columns: 60px 1fr;
  }

  .route-check {
    grid-column: 2;
    padding: 15px 0 0;
    border-top: 1px solid var(--line);
    border-left: 0;
  }

  .install-callout {
    grid-column: auto;
  }

  .trouble-heading {
    grid-template-columns: 1fr;
    gap: 20px;
  }

  .faq-heading {
    position: static;
  }

  .final-section {
    grid-template-columns: 100px 1fr;
  }

  .final-button {
    grid-column: 2;
    width: 250px;
  }

  .footer-shell {
    grid-template-columns: 1fr;
  }

  .copyright {
    grid-column: auto;
  }
}

@media (max-width: 600px) {
  body {
    padding-bottom: 70px;
  }

  .header-shell,
  .hero,
  .section,
  .final-section,
  .footer-shell {
    width: min(calc(100% - 28px), var(--shell));
  }

  .brand-plate {
    min-width: 165px;
  }

  .hero {
    padding-top: 56px;
    padding-bottom: 56px;
  }

  .hero h1 {
    font-size: clamp(44px, 14vw, 64px);
  }

  .hero-lead {
    font-size: 16px;
  }

  .hero-actions {
    display: grid;
  }

  .primary-button,
  .secondary-button {
    width: 100%;
  }

  .hero-answer {
    grid-template-columns: 1fr;
    gap: 7px;
    text-align: center;
  }

  .section {
    padding-top: 68px;
    padding-bottom: 68px;
  }

  .direct-intro h2,
  .section-heading h2,
  .difference-copy h2,
  .install-heading h2,
  .source-title h2,
  .trouble-heading h2,
  .faq-heading h2,
  .related-heading h2 {
    font-size: clamp(29px, 9vw, 39px);
  }

  .direct-action {
    grid-template-columns: 50px 1fr;
  }

  .action-divider {
    display: none;
  }

  .direct-action > div:nth-of-type(4) {
    grid-column: 2;
  }

  .direct-action a {
    grid-column: 2;
    width: 100%;
  }

  .route-list article {
    grid-template-columns: 50px 1fr;
    gap: 14px;
  }

  .route-code {
    width: 44px;
    height: 44px;
  }

  .difference-points article {
    grid-template-columns: 1fr;
    gap: 5px;
  }

  .install-steps li {
    grid-template-columns: 60px 1fr;
    gap: 15px;
  }

  .step-number {
    font-size: 25px;
  }

  .install-callout {
    grid-template-columns: 1fr;
  }

  .install-callout a {
    width: 100%;
  }

  .source-list article {
    grid-template-columns: 36px 1fr;
    gap: 12px;
  }

  .trouble-grid {
    grid-template-columns: 1fr;
  }

  .trouble-grid article {
    min-height: 0;
  }

  .faq-list summary {
    font-size: 15px;
  }

  .related-links {
    grid-template-columns: 1fr;
  }

  .related-links a:last-child {
    grid-column: auto;
  }

  .final-section {
    grid-template-columns: 1fr;
    padding: 34px 23px;
  }

  .final-index {
    font-size: 58px;
  }

  .final-button {
    grid-column: auto;
    width: 100%;
  }

  .footer-nav {
    grid-template-columns: 1fr 1fr;
  }

  .mobile-download {
    position: fixed;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 120;
    min-height: 70px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    padding: 9px 14px;
    color: var(--white);
    background: rgba(23, 23, 23, 0.97);
    border-top: 1px solid #333;
  }

  .mobile-download > div {
    display: flex;
    align-items: center;
    gap: 10px;
  }

  .mobile-download img {
    width: 44px;
    height: 44px;
    object-fit: contain;
    border-radius: 10px;
  }

  .mobile-download small,
  .mobile-download strong {
    display: block;
    line-height: 1.2;
  }

  .mobile-download small {
    color: #777;
    font-size: 10px;
  }

  .mobile-download strong {
    margin-top: 3px;
    font-size: 13px;
  }

  .mobile-download > a {
    padding: 11px 15px;
    color: var(--white);
    background: var(--red);
    font-size: 13px;
    font-weight: 900;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    transition-duration: 0.01ms !important;
  }
}