:root {
  --ink: #1f2d36;
  --muted: #64737e;
  --paper: #fbfcf8;
  --surface: #ffffff;
  --teal: #1f9e9a;
  --teal-dark: #146f75;
  --coral: #ff6f61;
  --gold: #ffd166;
  --mint: #dff6ed;
  --line: #dce7e4;
  --shadow: 0 18px 60px rgba(31, 45, 54, 0.16);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: "Microsoft YaHei", "PingFang SC", "Hiragino Sans GB", Arial, sans-serif;
  letter-spacing: 0;
}

body.nav-open {
  overflow: hidden;
}

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

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

.container {
  width: min(1120px, calc(100% - 40px));
  margin: 0 auto;
}

.site-header {
  position: fixed;
  z-index: 20;
  top: 0;
  left: 0;
  right: 0;
  height: 72px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 max(20px, calc((100vw - 1120px) / 2));
  background: rgba(255, 255, 255, 0.86);
  border-bottom: 1px solid rgba(220, 231, 228, 0.76);
  backdrop-filter: blur(18px);
}

.site-header.is-scrolled {
  box-shadow: 0 10px 30px rgba(31, 45, 54, 0.08);
}

.brand,
.footer-brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 800;
}

.brand__icon,
.footer-brand img {
  width: 40px;
  height: 40px;
  border-radius: 8px;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 6px;
  color: #263944;
  font-weight: 700;
}

.site-nav a {
  min-height: 40px;
  display: inline-flex;
  align-items: center;
  padding: 0 14px;
  border-radius: 8px;
}

.site-nav a:hover,
.site-nav a:focus-visible {
  color: var(--teal-dark);
  background: var(--mint);
  outline: none;
}

.nav-toggle {
  width: 44px;
  height: 44px;
  display: none;
  align-items: center;
  justify-content: center;
  color: var(--ink);
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 8px;
}

.nav-toggle svg,
.button svg,
.platform-card__icon svg,
.feature-card svg,
.about-list svg {
  width: 20px;
  height: 20px;
  stroke-width: 2.3;
}

.hero {
  position: relative;
  min-height: 78svh;
  display: flex;
  align-items: center;
  padding: 112px 0 54px;
  color: #ffffff;
  background:
    linear-gradient(90deg, rgba(20, 35, 44, 0.84) 0%, rgba(20, 35, 44, 0.58) 38%, rgba(20, 35, 44, 0.1) 70%),
    url("assets/baihedao-hero.png") center / cover no-repeat;
}

.hero::after {
  content: "";
  position: absolute;
  inset: auto 0 0;
  height: 140px;
  background: linear-gradient(0deg, rgba(31, 45, 54, 0.2), rgba(31, 45, 54, 0));
  pointer-events: none;
}

.hero__content {
  position: relative;
  z-index: 1;
  max-width: 650px;
  margin-left: max(20px, calc((100vw - 1120px) / 2));
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin: 0 0 22px;
  color: #f4fffd;
  font-size: 0.95rem;
  font-weight: 800;
}

.eyebrow img {
  width: 38px;
  height: 38px;
  border-radius: 8px;
  box-shadow: 0 10px 24px rgba(0, 0, 0, 0.22);
}

.hero h1 {
  margin: 0;
  font-size: 4.75rem;
  line-height: 1.02;
  font-weight: 900;
}

.hero__copy {
  max-width: 590px;
  margin: 22px 0 0;
  color: rgba(255, 255, 255, 0.9);
  font-size: 1.15rem;
  line-height: 1.9;
}

.download-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 32px;
}

.button {
  min-height: 48px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 9px;
  padding: 0 18px;
  border: 1px solid transparent;
  border-radius: 8px;
  font-weight: 800;
  white-space: nowrap;
  transition: transform 160ms ease, box-shadow 160ms ease, background 160ms ease;
}

.button:hover,
.button:focus-visible {
  transform: translateY(-1px);
  outline: none;
}

.button--primary {
  color: #12323a;
  background: var(--gold);
  box-shadow: 0 16px 32px rgba(0, 0, 0, 0.22);
}

.button--light {
  color: #ffffff;
  background: rgba(255, 255, 255, 0.16);
  border-color: rgba(255, 255, 255, 0.5);
}

.button--dark {
  color: #ffffff;
  background: var(--ink);
}

.hero__facts {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 28px;
}

.hero__facts span {
  min-height: 34px;
  display: inline-flex;
  align-items: center;
  padding: 0 12px;
  color: #f7fffd;
  background: rgba(255, 255, 255, 0.14);
  border: 1px solid rgba(255, 255, 255, 0.34);
  border-radius: 8px;
  font-size: 0.92rem;
  font-weight: 700;
}

.download-band,
.features-band,
.about-band {
  padding: 74px 0;
}

.download-band {
  background: var(--surface);
}

.features-band {
  background: #eef7f4;
}

.about-band {
  color: #f4fffd;
  background: #153a3a;
}

.section-heading {
  max-width: 680px;
  margin: 0 auto 34px;
  text-align: center;
}

.section-heading--left {
  margin-left: 0;
  text-align: left;
}

.section-kicker {
  margin: 0 0 8px;
  color: var(--coral);
  font-weight: 900;
}

.section-heading h2,
.about-copy h2 {
  margin: 0;
  font-size: 2.25rem;
  line-height: 1.2;
}

.section-heading p:last-child,
.about-copy p:last-child {
  margin: 14px 0 0;
  color: var(--muted);
  line-height: 1.8;
}

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

.platform-card {
  min-height: 230px;
  display: grid;
  grid-template-rows: auto 1fr auto;
  gap: 16px;
  padding: 24px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 8px;
  box-shadow: var(--shadow);
}

.platform-card__icon {
  width: 48px;
  height: 48px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: #073736;
  background: var(--mint);
  border-radius: 8px;
}

.platform-card__icon--coral {
  color: #491f1a;
  background: #ffe2df;
}

.platform-card h3,
.feature-card h3 {
  margin: 0 0 8px;
  font-size: 1.25rem;
}

.platform-card p,
.feature-card p {
  margin: 0;
  color: var(--muted);
  line-height: 1.75;
}

.feature-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 14px;
}

.feature-card {
  min-height: 188px;
  padding: 22px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 8px;
}

.feature-card svg {
  width: 30px;
  height: 30px;
  margin-bottom: 18px;
  color: var(--teal);
}

.about-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(320px, 420px);
  gap: 52px;
  align-items: center;
}

.about-copy p:last-child {
  color: rgba(244, 255, 253, 0.78);
}

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

.about-list div {
  min-height: 64px;
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 0 16px;
  color: var(--ink);
  background: #ffffff;
  border-radius: 8px;
}

.about-list svg {
  flex: 0 0 auto;
  color: var(--coral);
}

.site-footer {
  padding: 34px 0;
  color: #465660;
  background: #ffffff;
  border-top: 1px solid var(--line);
}

.footer-layout {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.footer-layout p {
  margin: 10px 0 0;
}

.footer-meta {
  display: grid;
  gap: 8px;
  justify-items: end;
}

.footer-meta a {
  color: var(--teal-dark);
  font-weight: 800;
}

.toast {
  position: fixed;
  z-index: 40;
  left: 50%;
  bottom: 24px;
  width: min(520px, calc(100% - 32px));
  padding: 14px 16px;
  color: #ffffff;
  background: rgba(31, 45, 54, 0.94);
  border-radius: 8px;
  box-shadow: var(--shadow);
  opacity: 0;
  pointer-events: none;
  transform: translate(-50%, 12px);
  transition: opacity 180ms ease, transform 180ms ease;
}

.toast.is-visible {
  opacity: 1;
  transform: translate(-50%, 0);
}

@media (max-width: 900px) {
  .hero {
    background-position: 58% center;
  }

  .hero h1 {
    font-size: 3.6rem;
  }

  .feature-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .about-layout {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 720px) {
  .container {
    width: min(100% - 28px, 1120px);
  }

  .site-header {
    height: 64px;
    padding: 0 14px;
  }

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

  .site-nav {
    position: fixed;
    top: 64px;
    left: 14px;
    right: 14px;
    display: grid;
    gap: 4px;
    padding: 10px;
    background: #ffffff;
    border: 1px solid var(--line);
    border-radius: 8px;
    box-shadow: var(--shadow);
    opacity: 0;
    pointer-events: none;
    transform: translateY(-8px);
    transition: opacity 160ms ease, transform 160ms ease;
  }

  body.nav-open .site-nav {
    opacity: 1;
    pointer-events: auto;
    transform: translateY(0);
  }

  .site-nav a {
    justify-content: center;
  }

  .hero {
    min-height: 74svh;
    padding: 92px 0 40px;
    background-position: 59% center;
  }

  .hero__content {
    max-width: none;
    margin-left: auto;
  }

  .hero h1 {
    font-size: 3rem;
  }

  .hero__copy {
    font-size: 1rem;
    line-height: 1.78;
  }

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

  .button {
    width: 100%;
  }

  .download-band,
  .features-band,
  .about-band {
    padding: 54px 0;
  }

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

  .section-heading,
  .section-heading--left {
    text-align: left;
  }

  .section-heading h2,
  .about-copy h2 {
    font-size: 1.85rem;
  }

  .footer-layout {
    display: grid;
  }

  .footer-meta {
    justify-items: start;
  }
}

@media (max-width: 390px) {
  .hero h1 {
    font-size: 2.55rem;
  }

  .hero__facts span {
    width: calc(50% - 5px);
    justify-content: center;
  }

  .hero__facts span:last-child {
    width: 100%;
  }
}