:root {
  --bg: #f5f7fb;
  --card: #fff;
  --text: #222f3e;
  --muted: #667085;
  --line: #e5eaf2;
  --brand: #1a73e8;
  --brand-dark: #0f5fcf;
  --soft: #eef5ff;
  --shadow: 0 10px 28px rgba(31, 41, 55, 0.08);
  --radius: 16px;
  --container: 1180px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: "Microsoft YaHei", "PingFang SC", Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.75;
}

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

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

.container {
  width: min(var(--container), calc(100% - 32px));
  margin: 0 auto;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.96);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(10px);
}

.nav-row {
  min-height: 70px;
  display: flex;
  align-items: center;
  gap: 24px;
}

.logo,
.footer-logo {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  white-space: nowrap;
}

.logo {
  font-size: 20px;
}

.site-nav {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 30px;
  color: #4b5563;
  font-size: 15px;
}

.site-nav a:hover,
.site-nav a.is-active {
  color: var(--brand);
}

.menu-btn {
  display: none;
  margin-left: auto;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: #fff;
  padding: 8px 16px;
  color: var(--text);
}

.hero {
  padding: 28px 0 20px;
}

.crumb {
  margin-bottom: 14px;
  color: var(--muted);
  font-size: 13px;
}

.hero-card {
  display: grid;
  grid-template-columns: minmax(0, 1.25fr) minmax(300px, 0.75fr);
  gap: 20px;
}

.hero-info,
.content-card,
.hero-preview,
.final-card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.hero-info {
  padding: 26px;
}

.product-title {
  display: flex;
  align-items: flex-start;
  gap: 18px;
}

h1,
h2,
p {
  margin: 0;
}

h1 {
  margin-bottom: 8px;
  font-size: clamp(28px, 3.8vw, 42px);
  line-height: 1.2;
}

h2 {
  margin-bottom: 14px;
  font-size: 24px;
  line-height: 1.25;
}

.product-title p,
.tip,
.content-card p,
.final-card p {
  color: var(--muted);
}

.version-table {
  margin-top: 22px;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  padding: 16px;
  border-radius: 14px;
  background: #f8fbff;
  border: 1px solid #dceaff;
}

.version-table div {
  min-height: 34px;
}

.version-table span {
  color: var(--muted);
}

.download-row,
.final-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 22px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  padding: 0 24px;
  border-radius: 12px;
  border: 1px solid var(--line);
  background: #fff;
  color: var(--text);
  font-weight: 700;
  transition: 0.2s ease;
}

.btn:hover {
  transform: translateY(-1px);
  border-color: rgba(26, 115, 232, 0.45);
  color: var(--brand);
}

.btn-primary {
  color: #fff;
  border-color: transparent;
  background: linear-gradient(180deg, #2f88ff, var(--brand));
  box-shadow: 0 10px 22px rgba(26, 115, 232, 0.25);
}

.btn-primary:hover {
  color: #fff;
  background: linear-gradient(180deg, #227af0, var(--brand-dark));
}

.btn-light {
  color: #fff;
  background: rgba(255, 255, 255, 0.14);
  border-color: rgba(255, 255, 255, 0.28);
}

.btn-light:hover {
  color: #fff;
  border-color: rgba(255, 255, 255, 0.6);
}

.tip {
  margin-top: 14px;
  padding: 12px 14px;
  border-radius: 12px;
  background: #f8fafc;
  font-size: 14px;
}

.hero-preview {
  padding: 18px;
  align-self: stretch;
  display: flex;
  align-items: center;
}

.section {
  padding: 0 0 20px;
}

.content-card {
  padding: 24px;
}

.text-list {
  display: grid;
  gap: 12px;
}

.text-list strong {
  color: var(--text);
}

.screenshot-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
}

.screenshot-grid img {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fff;
  box-shadow: var(--shadow);
}

.two-col {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 20px;
}

.section-title-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  margin-bottom: 14px;
}

.section-title-row span {
  color: var(--brand);
  font-weight: 700;
}

.help-list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px 20px;
}

.help-list a {
  position: relative;
  padding-left: 14px;
  color: #344054;
}

.help-list a::before {
  content: "";
  position: absolute;
  left: 0;
  top: 13px;
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: var(--brand);
}

.help-list a:hover {
  color: var(--brand);
}

.final-card {
  padding: 28px;
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 20px;
  align-items: center;
  color: #fff;
  background: linear-gradient(135deg, var(--brand), #1149b8);
}

.final-card p,
.final-card h2 {
  color: #fff;
}

.final-card p {
  opacity: 0.86;
}

.site-footer {
  background: #fff;
  border-top: 1px solid var(--line);
  margin-top: 14px;
}

.footer-row {
  min-height: 76px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  flex-wrap: wrap;
}

.footer-links {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  color: var(--muted);
  font-size: 14px;
}

.footer-links a:hover {
  color: var(--brand);
}

.back-top {
  position: fixed;
  right: 18px;
  bottom: 18px;
  z-index: 40;
  min-height: 44px;
  padding: 0 16px;
  border: 0;
  border-radius: 999px;
  background: #111827;
  color: #fff;
  box-shadow: 0 10px 24px rgba(17, 24, 39, 0.24);
  cursor: pointer;
  opacity: 0;
  pointer-events: none;
  transform: translateY(8px);
  transition: 0.2s ease;
}

.back-top.is-visible {
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0);
}

@media (max-width: 960px) {
  .hero-card,
  .two-col,
  .final-card {
    grid-template-columns: 1fr;
  }

  .final-actions {
    margin-top: 0;
  }
}

@media (max-width: 720px) {
  .container {
    width: min(var(--container), calc(100% - 24px));
  }

  .nav-row {
    flex-wrap: wrap;
    padding: 12px 0;
  }

  .menu-btn {
    display: inline-flex;
  }

  .site-nav {
    display: none;
    width: 100%;
    margin-left: 0;
    flex-direction: column;
    align-items: flex-start;
    gap: 12px;
    padding-bottom: 8px;
  }

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

  .product-title {
    flex-direction: column;
  }

  .version-table,
  .screenshot-grid,
  .help-list {
    grid-template-columns: 1fr;
  }

  .download-row,
  .final-actions {
    flex-direction: column;
  }

  .btn {
    width: 100%;
  }
}