:root {
  --brand: #2e79dc;
  --brand-light: #79bcf4;
  --ink: #0f1115;
  --muted: #6595c6;
  --page-width: 1440px;
}

/* 所有页面使用一致的盒模型，保证设计稿尺寸可以稳定换算。 */
*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  min-width: 320px;
  background: #fff;
}

body {
  margin: 0;
  color: var(--ink);
  font-family: Arial, Helvetica, sans-serif;
  -webkit-font-smoothing: antialiased;
}

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

.page-shell {
  width: min(100%, var(--page-width));
  margin-inline: auto;
  padding-inline: 28px;
}

/* 首页 */
.home-page {
  min-height: 100vh;
  overflow-x: hidden;
  background:
    radial-gradient(circle at 17% 55%, rgba(217, 247, 255, 0.9), transparent 29%),
    radial-gradient(circle at 82% 54%, rgba(225, 217, 255, 0.78), transparent 31%),
    #f8fbff;
}

.site-header {
  position: relative;
  z-index: 10;
  min-height: 178px;
  padding-top: 42px;
}

.wordmark {
  display: inline-block;
  color: var(--brand);
  font-size: 22px;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.primary-nav {
  margin-top: 43px;
  padding-left: 100px;
}

.primary-nav a {
  color: var(--brand);
  font-size: 18px;
  font-weight: 600;
}

.age-notice {
  position: relative;
  z-index: 10;
  margin: -2px 24px 0;
  color: #13a916;
  font-size: clamp(19px, 1.55vw, 24px);
  font-weight: 800;
  text-align: center;
}

.download-hero {
  position: relative;
  isolation: isolate;
  display: grid;
  min-height: 592px;
  place-items: start center;
  overflow: hidden;
  padding-top: 78px;
}

.download-hero::before {
  position: absolute;
  z-index: -3;
  inset: 0;
  background:
    radial-gradient(ellipse at 49% 36%, rgba(255, 255, 255, 0.98) 0 17%, rgba(250, 247, 255, 0.65) 35%, transparent 56%),
    linear-gradient(135deg, rgba(224, 247, 255, 0.72), rgba(250, 247, 255, 0.78) 48%, rgba(229, 224, 255, 0.72));
  content: "";
}

.ambient {
  position: absolute;
  z-index: -2;
  width: 620px;
  height: 360px;
  border-radius: 50%;
  filter: blur(34px);
  opacity: 0.72;
}

.ambient-one {
  top: 210px;
  left: -120px;
  background: rgba(194, 239, 255, 0.78);
  transform: rotate(-17deg);
}

.ambient-two {
  right: -110px;
  bottom: -20px;
  background: rgba(216, 205, 255, 0.82);
  transform: rotate(12deg);
}

.ribbon {
  position: absolute;
  z-index: -1;
  width: 120%;
  height: 260px;
  border: 5px solid rgba(255, 255, 255, 0.78);
  border-radius: 50%;
  filter: drop-shadow(0 8px 18px rgba(124, 168, 231, 0.13));
}

.ribbon-one {
  top: 160px;
  left: -16%;
  transform: rotate(-11deg);
}

.ribbon-two {
  right: -18%;
  bottom: -90px;
  transform: rotate(12deg);
}

.hero-content {
  position: relative;
  z-index: 2;
  display: flex;
  align-items: center;
  flex-direction: column;
}

.logo-card {
  display: grid;
  width: 158px;
  height: 158px;
  place-items: center;
  border: 1px solid rgba(255, 255, 255, 0.92);
  border-radius: 38px;
  background: rgba(255, 255, 255, 0.9);
  box-shadow: 0 14px 38px rgba(74, 112, 173, 0.22), 0 2px 8px rgba(76, 111, 164, 0.12);
  backdrop-filter: blur(12px);
}

.logo-card img {
  width: 113px;
  height: 113px;
}

.hero-content h1 {
  margin: 23px 0 30px;
  color: var(--brand);
  font-size: 27px;
  line-height: 1;
}

.download-button {
  display: grid;
  width: 330px;
  height: 96px;
  place-items: center;
  border-radius: 34px;
  color: #fff;
  background: linear-gradient(100deg, #2787ef, #79bff1);
  box-shadow: 0 15px 34px rgba(47, 132, 230, 0.22);
  font-size: 18px;
  font-weight: 700;
  transition: transform 180ms ease, box-shadow 180ms ease;
}

.download-button:hover,
.download-button:focus-visible {
  transform: translateY(-3px);
  box-shadow: 0 19px 40px rgba(47, 132, 230, 0.3);
  outline: none;
}

.download-note {
  margin: 29px 0 0;
  color: var(--brand);
  font-size: 17px;
  font-weight: 600;
  line-height: 1.55;
  text-align: center;
}

.site-footer {
  position: relative;
  z-index: 5;
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  min-height: 250px;
  padding-top: 36px;
  padding-bottom: 52px;
  color: var(--muted);
  background: rgba(255, 255, 255, 0.2);
}

.footer-column {
  justify-self: center;
  min-width: 230px;
}

.footer-column h2,
.footer-heading {
  display: inline-block;
  margin: 0 0 27px;
  color: var(--brand);
  font-size: 17px;
  font-weight: 700;
}

.footer-heading:hover,
.footer-heading:focus-visible {
  text-decoration: underline;
  text-underline-offset: 5px;
}

.footer-column p,
.footer-column > a:not(.footer-heading) {
  display: block;
  margin: 0 0 10px;
  font-size: 15px;
  line-height: 1.4;
}

/* About Us 页面 */
.about-page {
  min-height: 100vh;
  background: #fff;
}

.about-shell {
  position: relative;
  width: min(100%, var(--page-width));
  min-height: 1145px;
  margin-inline: auto;
  padding: 58px 120px 90px;
}

.back-link {
  position: absolute;
  top: 62px;
  left: 31px;
  color: #2e69bc;
  font-size: 36px;
  font-weight: 400;
  line-height: 1;
  transition: transform 160ms ease;
}

.back-link:hover,
.back-link:focus-visible {
  transform: translateX(-4px);
  outline: none;
}

.about-brand {
  display: flex;
  align-items: center;
  gap: 22px;
  color: #2b6fca;
  font-size: 43px;
  font-weight: 700;
}

.about-brand img {
  width: 128px;
  height: 128px;
}

.about-brand .flag {
  width: 89px;
  height: 59px;
  margin-left: 4px;
  object-fit: contain;
  filter: saturate(0.95);
}

.letter {
  max-width: 1090px;
  margin-top: 47px;
  font-size: 20px;
  font-weight: 700;
  line-height: 1.52;
  letter-spacing: 0.005em;
}

.letter p {
  margin: 0 0 34px;
}

.letter .signature {
  margin-top: 46px;
  line-height: 1.5;
}

/* 设计稿是桌面端，这里补足移动端换行和可点击尺寸。 */
@media (max-width: 760px) {
  .site-header {
    min-height: 132px;
    padding-top: 28px;
  }

  .primary-nav {
    margin-top: 28px;
    padding-left: 42px;
  }

  .age-notice {
    font-size: 16px;
  }

  .download-hero {
    min-height: 570px;
    padding-top: 58px;
  }

  .logo-card {
    width: 132px;
    height: 132px;
    border-radius: 31px;
  }

  .logo-card img {
    width: 94px;
    height: 94px;
  }

  .download-button {
    width: min(78vw, 330px);
    height: 76px;
  }

  .download-note {
    padding-inline: 24px;
    font-size: 14px;
  }

  .site-footer {
    grid-template-columns: 1fr;
    gap: 34px;
    padding-top: 38px;
  }

  .footer-column {
    width: 100%;
    min-width: 0;
    justify-self: start;
    padding-left: 16px;
  }

  .footer-column h2,
  .footer-heading {
    margin-bottom: 14px;
  }

  .about-shell {
    min-height: 100vh;
    padding: 34px 25px 64px;
  }

  .back-link {
    top: 31px;
    left: 18px;
  }

  .about-brand {
    justify-content: center;
    gap: 10px;
    padding-left: 22px;
    font-size: clamp(25px, 8vw, 38px);
  }

  .about-brand img {
    width: 84px;
    height: 84px;
  }

  .about-brand .flag {
    width: 59px;
    height: 39px;
  }

  .letter {
    margin-top: 42px;
    font-size: 16px;
    line-height: 1.6;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition-duration: 0.01ms !important;
  }
}