:root {
  --blue: #2f6df6;
  --blue-dark: #1f4fd0;
  --blue-soft: #eef4ff;
  --ink: #171b24;
  --muted: #596273;
  --line: #e7ecf3;
  --bg: #f6f8fb;
  --card: #ffffff;
  --soft-card: #f9fbff;
  --shadow: 0 20px 60px rgba(26, 43, 72, .08);
  --radius-lg: 28px;
  --radius-md: 20px;
  --radius-sm: 14px;
  --container: 1180px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  background: #fff;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", Arial, sans-serif;
  line-height: 1.7;
  overflow-x: hidden;
}

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

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

.container {
  width: min(var(--container), calc(100% - 40px));
  margin: 0 auto;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  height: 74px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 max(22px, calc((100vw - var(--container)) / 2));
  background: rgba(255, 255, 255, .92);
  backdrop-filter: saturate(180%) blur(18px);
  border-bottom: 1px solid rgba(220, 227, 238, .85);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  min-width: 0;
  font-weight: 800;
  font-size: 20px;
  letter-spacing: -.02em;
}

.brand img {
  width: 42px;
  height: 42px;
  object-fit: contain;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 30px;
  color: #263042;
  font-size: 15px;
  font-weight: 600;
}

.site-nav a {
  position: relative;
  padding: 6px 0;
}

.site-nav a::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 2px;
  background: var(--blue);
  border-radius: 999px;
  transform: scaleX(0);
  transform-origin: center;
  transition: transform .2s ease;
}

.site-nav a:hover::after {
  transform: scaleX(1);
}

.nav-toggle {
  display: none;
  border: 1px solid var(--line);
  background: #fff;
  color: var(--ink);
  border-radius: 999px;
  padding: 9px 14px;
  font-weight: 700;
}

.hero {
  position: relative;
  overflow: hidden;
  background: linear-gradient(135deg, #eef5ff 0%, #f7faff 45%, #edf3fb 100%);
}

.hero-bg {
  position: absolute;
  inset: 0;
  background-image: linear-gradient(120deg, rgba(14, 35, 58, .55), rgba(44, 96, 140, .42)), url("../img/header-bg.jpg");
  background-size: cover;
  background-position: center;
  opacity: .88;
}

.home-hero {
  border-radius: 0 0 22px 22px;
}

.download-hero {
  border-radius: 0 0 22px 22px;
}

.hero-grid {
  position: relative;
  min-height: 600px;
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(300px, .95fr);
  align-items: center;
  gap: 80px;
  padding: 70px 0;
}

.hero-grid.compact {
  min-height: 430px;
  grid-template-columns: minmax(0, 1fr) minmax(320px, .65fr);
}

.hero-copy {
  color: #fff;
  max-width: 620px;
}

.eyebrow {
  margin: 0 0 12px;
  color: var(--blue);
  font-size: 14px;
  line-height: 1.3;
  font-weight: 800;
  letter-spacing: .08em;
  text-transform: uppercase;
}

.hero .eyebrow {
  color: rgba(255, 255, 255, .9);
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1 {
  margin-bottom: 20px;
  font-size: clamp(42px, 7vw, 74px);
  line-height: 1.04;
  letter-spacing: -.055em;
}

h2 {
  margin-bottom: 16px;
  font-size: clamp(28px, 4vw, 44px);
  line-height: 1.2;
  letter-spacing: -.04em;
}

h3 {
  margin-bottom: 12px;
  font-size: 22px;
  line-height: 1.35;
  letter-spacing: -.02em;
}

.hero-text {
  max-width: 650px;
  margin-bottom: 32px;
  color: rgba(255, 255, 255, .9);
  font-size: 19px;
  font-weight: 600;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  margin-bottom: 24px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 50px;
  padding: 13px 24px;
  border-radius: 13px;
  border: 1px solid transparent;
  font-size: 16px;
  font-weight: 800;
  line-height: 1.2;
  cursor: pointer;
  transition: transform .18s ease, box-shadow .18s ease, background .18s ease;
}

.btn:hover {
  transform: translateY(-2px);
}

.btn-primary {
  color: #fff;
  background: linear-gradient(135deg, #2f79ff, #2563ed);
  box-shadow: 0 16px 34px rgba(31, 96, 224, .28);
}

.btn-primary:hover {
  background: linear-gradient(135deg, #377fff, #1e55d7);
  box-shadow: 0 20px 44px rgba(31, 96, 224, .36);
}

.btn-soft {
  color: #fff;
  background: rgba(255, 255, 255, .14);
  border-color: rgba(255, 255, 255, .24);
  box-shadow: 0 16px 34px rgba(19, 33, 56, .12);
}

.btn-soft:hover {
  background: rgba(255, 255, 255, .22);
}

.btn.full {
  width: 100%;
}

.hero-note {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.hero-note span {
  padding: 7px 12px;
  border: 1px solid rgba(255, 255, 255, .24);
  border-radius: 999px;
  color: rgba(255, 255, 255, .92);
  background: rgba(255, 255, 255, .12);
  font-weight: 700;
  font-size: 13px;
}

.hero-visual {
  display: flex;
  justify-content: center;
  align-items: center;
}

.hero-visual img {
  width: min(390px, 90%);
  filter: drop-shadow(0 36px 50px rgba(0, 0, 0, .32));
  transform: translateY(8px);
}

.quick-panel {
  padding: 58px 0 30px;
}

.quick-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 22px;
}

.quick-card {
  min-height: 128px;
  padding: 26px 24px;
  border-radius: 22px;
  background: var(--soft-card);
  box-shadow: var(--shadow);
  border: 1px solid rgba(232, 237, 247, .9);
}

.quick-card strong {
  display: block;
  color: var(--blue);
  font-size: 27px;
  line-height: 1.15;
  margin-bottom: 8px;
}

.quick-card span {
  color: var(--muted);
  font-weight: 650;
}

.section {
  padding: 86px 0;
}

.section.muted {
  background: var(--bg);
}

.section-heading {
  max-width: 840px;
  margin: 0 auto 46px;
  text-align: center;
}

.section-heading p:not(.eyebrow) {
  color: var(--muted);
  font-size: 18px;
}

.section-heading.narrow {
  max-width: 760px;
}

.version-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 22px;
}

.version-card {
  min-height: 320px;
  padding: 28px;
  border-radius: var(--radius-md);
  background: #fff;
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
  transition: transform .2s ease, box-shadow .2s ease;
}

.version-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 22px 68px rgba(27, 45, 76, .13);
}

.version-icon {
  width: 62px;
  height: 62px;
  display: grid;
  place-items: center;
  margin-bottom: 22px;
  color: var(--blue);
  background: var(--blue-soft);
  border: 1px solid #dce7ff;
  border-radius: 18px;
  font-weight: 900;
}

.version-card p,
.feature-media-card p,
.mini-feature-grid p,
.prep-grid p,
.download-card p,
.footer-brand p {
  color: var(--muted);
}

.text-link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-top: 8px;
  color: var(--blue);
  font-weight: 900;
}

.text-link::after {
  content: "›";
  font-size: 23px;
  line-height: 1;
}

.feature-layout {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 28px;
  margin-bottom: 28px;
}

.feature-media-card {
  display: flex;
  min-height: 360px;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 44px 34px;
  border-radius: var(--radius-lg);
  background: #fff;
  border: 1px solid rgba(234, 239, 248, .95);
  box-shadow: var(--shadow);
}

.feature-media-card img {
  width: 210px;
  height: 170px;
  object-fit: contain;
  margin-bottom: 28px;
}

.mini-feature-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 18px;
}

.mini-feature-grid article,
.prep-grid article {
  padding: 26px;
  border-radius: 20px;
  background: #fff;
  border: 1px solid rgba(231, 236, 245, .95);
  box-shadow: 0 12px 36px rgba(29, 45, 74, .06);
}

.split-card,
.safety-box,
.download-band {
  display: grid;
  grid-template-columns: minmax(0, .9fr) minmax(330px, 1fr);
  gap: 42px;
  align-items: center;
  padding: 42px;
  border-radius: var(--radius-lg);
  background: #fff;
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
}

.split-card p,
.safety-box p,
.download-band p {
  color: var(--muted);
  font-size: 17px;
}

.check-list,
.safe-list {
  display: grid;
  gap: 14px;
}

.check-list div,
.safe-list div {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 16px 18px;
  border-radius: 16px;
  color: #243047;
  background: var(--blue-soft);
  font-weight: 800;
}

.check-list span {
  width: 11px;
  height: 11px;
  flex: 0 0 auto;
  border-radius: 50%;
  background: var(--blue);
  box-shadow: 0 0 0 5px rgba(47, 109, 246, .13);
}

.download-band {
  grid-template-columns: minmax(0, 1fr) auto;
}

.faq-list {
  max-width: 920px;
  margin: 0 auto;
  display: grid;
  gap: 14px;
}

.faq-list details {
  padding: 22px 26px;
  border-radius: 18px;
  background: #fff;
  border: 1px solid var(--line);
  box-shadow: 0 12px 34px rgba(28, 42, 64, .05);
}

.faq-list summary {
  cursor: pointer;
  font-size: 18px;
  font-weight: 900;
  list-style: none;
}

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

.faq-list summary::after {
  content: "+";
  float: right;
  color: var(--blue);
  font-size: 22px;
  line-height: 1;
}

.faq-list details[open] summary::after {
  content: "–";
}

.faq-list p {
  margin: 12px 0 0;
  color: var(--muted);
}

.download-summary {
  display: grid;
  gap: 16px;
}

.download-summary div {
  padding: 22px 24px;
  border-radius: 18px;
  background: rgba(255, 255, 255, .16);
  border: 1px solid rgba(255, 255, 255, .24);
  color: #fff;
  backdrop-filter: blur(14px);
}

.download-summary strong {
  display: block;
  font-size: 24px;
  margin-bottom: 3px;
}

.download-summary span {
  color: rgba(255, 255, 255, .82);
  font-weight: 700;
}

.download-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 24px;
}

.download-card {
  padding: 32px;
  border-radius: var(--radius-lg);
  background: #fff;
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
}

.download-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 24px;
}

.badge {
  display: inline-flex;
  align-items: center;
  min-height: 34px;
  padding: 6px 12px;
  border-radius: 999px;
  color: var(--blue-dark);
  background: var(--blue-soft);
  font-weight: 900;
}

.download-head strong {
  color: #738095;
}

.download-card ul {
  margin: 18px 0 24px;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 10px;
}

.download-card li {
  position: relative;
  padding-left: 22px;
  color: #2d384b;
  font-weight: 650;
}

.download-card li::before {
  content: "";
  position: absolute;
  left: 0;
  top: .72em;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--blue);
}

.prep-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
}

.safe-list div::before {
  content: "";
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--blue);
  box-shadow: 0 0 0 5px rgba(47, 109, 246, .13);
  flex: 0 0 auto;
}

.site-footer {
  background: #f1f3f6;
  padding: 58px 0 26px;
  color: #2b3445;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.4fr repeat(3, 1fr);
  gap: 50px;
}

.footer-brand strong {
  display: block;
  margin: 12px 0 8px;
  font-size: 20px;
}

.site-footer h2 {
  margin-bottom: 12px;
  font-size: 17px;
  line-height: 1.3;
  letter-spacing: 0;
}

.site-footer a {
  display: block;
  color: #4d586b;
  margin: 8px 0;
}

.site-footer a:hover {
  color: var(--blue);
}

.copyright {
  width: min(var(--container), calc(100% - 40px));
  margin: 36px auto 0;
  padding-top: 24px;
  border-top: 1px solid #dde3ec;
  color: #778194;
  text-align: center;
  font-size: 14px;
}

@media (max-width: 1020px) {
  .quick-grid,
  .version-grid,
  .mini-feature-grid,
  .prep-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .hero-grid,
  .hero-grid.compact,
  .split-card,
  .safety-box,
  .download-band {
    grid-template-columns: 1fr;
  }

  .hero-grid {
    gap: 30px;
    min-height: auto;
  }

  .hero-visual {
    justify-content: flex-start;
  }

  .download-grid,
  .feature-layout {
    grid-template-columns: 1fr;
  }

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

@media (max-width: 760px) {
  .container {
    width: min(100% - 28px, var(--container));
  }

  .site-header {
    height: 66px;
    padding: 0 14px;
  }

  .brand {
    font-size: 18px;
  }

  .brand img {
    width: 36px;
    height: 36px;
  }

  .nav-toggle {
    display: inline-flex;
  }

  .site-nav {
    position: absolute;
    left: 14px;
    right: 14px;
    top: 74px;
    display: none;
    flex-direction: column;
    align-items: flex-start;
    gap: 8px;
    padding: 16px;
    border-radius: 18px;
    background: #fff;
    border: 1px solid var(--line);
    box-shadow: 0 18px 48px rgba(22, 32, 55, .14);
  }

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

  .site-nav a {
    width: 100%;
    padding: 10px 4px;
  }

  .hero-grid,
  .hero-grid.compact {
    padding: 48px 0 42px;
  }

  .home-hero,
  .download-hero {
    border-radius: 0 0 16px 16px;
  }

  h1 {
    font-size: 44px;
  }

  h2 {
    font-size: 30px;
  }

  h3 {
    font-size: 20px;
  }

  .hero-text,
  .section-heading p:not(.eyebrow) {
    font-size: 16px;
  }

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

  .hero-actions .btn {
    width: 100%;
  }

  .hero-visual img {
    width: min(280px, 82vw);
  }

  .quick-panel {
    padding: 34px 0 12px;
  }

  .quick-grid,
  .version-grid,
  .mini-feature-grid,
  .prep-grid,
  .footer-grid {
    grid-template-columns: 1fr;
  }

  .section {
    padding: 58px 0;
  }

  .section-heading {
    margin-bottom: 30px;
    text-align: left;
  }

  .feature-media-card {
    min-height: 300px;
    padding: 32px 20px;
  }

  .split-card,
  .safety-box,
  .download-band,
  .download-card,
  .version-card {
    padding: 24px;
    border-radius: 20px;
  }

  .download-head {
    align-items: flex-start;
    flex-direction: column;
  }

  .site-footer {
    padding-top: 44px;
  }
}

@media (max-width: 420px) {
  .btn {
    padding-left: 18px;
    padding-right: 18px;
  }

  h1 {
    font-size: 38px;
  }

  .hero-note span {
    font-size: 12px;
  }
}