:root {
  color-scheme: light dark;
  --bg: #f4f7ff;
  --surface: #ffffff;
  --surface-soft: #eaf0ff;
  --ink: #0f1b33;
  --muted: #5b6680;
  --accent: #1b3fa8;
  --accent-2: #2f6bff;
  --line: #dbe4f8;
  --shadow: 0 18px 50px rgba(27, 63, 168, 0.12);
  --radius: 20px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #080f26;
    --surface: #101a38;
    --surface-soft: #16224a;
    --ink: #eef3ff;
    --muted: #a9b6d6;
    --accent: #dbe6ff;
    --accent-2: #7fa8ff;
    --line: #26345c;
    --shadow: 0 18px 50px rgba(0, 0, 0, 0.40);
  }
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  font-size: 16px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--accent-2);
  text-underline-offset: 3px;
}

a:hover {
  text-decoration-thickness: 2px;
}

.site-header {
  max-width: 980px;
  margin: 0 auto;
  padding: 22px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  flex-wrap: wrap;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  color: var(--ink);
  text-decoration: none;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.brand-mark {
  width: 34px;
  height: 34px;
  display: inline-flex;
  color: var(--accent);
}

.brand-mark svg {
  width: 100%;
  height: 100%;
}

.site-nav {
  display: flex;
  gap: 18px;
  font-size: 14px;
}

.site-nav a {
  color: var(--muted);
  text-decoration: none;
}

.site-nav a:hover {
  color: var(--ink);
}

html[data-lang="en"] [data-zh],
html[data-lang="en"] [data-zh-hant],
html[data-lang="zh"] [data-en],
html[data-lang="zh"] [data-zh-hant],
html[data-lang="zh-hant"] [data-en],
html[data-lang="zh-hant"] [data-zh] {
  display: none !important;
}

.lang-switch {
  display: inline-flex;
  gap: 4px;
  padding: 3px;
  background: var(--surface-soft);
  border: 1px solid var(--line);
  border-radius: 999px;
}

.lang-switch button {
  appearance: none;
  border: 0;
  background: transparent;
  color: var(--muted);
  font: inherit;
  font-size: 13px;
  font-weight: 700;
  line-height: 1;
  padding: 7px 13px;
  border-radius: 999px;
  cursor: pointer;
}

.lang-switch button:hover {
  color: var(--ink);
}

.lang-switch button.is-active {
  background: var(--accent);
  color: #fff;
}

main {
  max-width: 860px;
  margin: 0 auto;
  padding: 0 20px 72px;
}

.hero {
  padding: 46px 0 34px;
}

.app-mark {
  width: 112px;
  height: 112px;
  margin-bottom: 26px;
  border-radius: 27px;
  box-shadow: var(--shadow);
  overflow: hidden;
}

.app-mark svg {
  display: block;
  width: 100%;
  height: 100%;
}

.eyebrow {
  margin: 0 0 8px;
  color: var(--accent-2);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.10em;
  text-transform: uppercase;
}

h1 {
  margin: 0;
  font-size: clamp(34px, 6vw, 54px);
  line-height: 1.08;
  letter-spacing: -0.03em;
}

h2 {
  margin: 0 0 18px;
  font-size: 23px;
  line-height: 1.25;
  letter-spacing: -0.02em;
}

h3 {
  margin: 26px 0 8px;
  font-size: 17px;
}

.lede {
  max-width: 640px;
  margin: 16px 0 0;
  color: var(--muted);
  font-size: 18px;
}

.meta {
  margin: 14px 0 0;
  color: var(--muted);
  font-size: 14px;
}

.language-links {
  margin: 8px 0 0;
  font-size: 14px;
  color: var(--muted);
}

.language-links a {
  color: var(--accent-2);
  font-weight: 600;
  text-decoration: none;
}

.language-links a:hover {
  text-decoration: underline;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 26px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 46px;
  padding: 0 20px;
  border-radius: 999px;
  font-size: 15px;
  font-weight: 700;
  text-decoration: none;
  transition: transform 120ms ease, background-color 120ms ease, border-color 120ms ease;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn.primary {
  background: var(--accent);
  color: #fff;
  border: 1px solid var(--accent);
}

.btn.ghost {
  background: transparent;
  color: var(--ink);
  border: 1px solid var(--line);
}

.panel {
  margin-top: 24px;
  padding: 28px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: 0 8px 26px rgba(30, 58, 95, 0.04);
  scroll-margin-top: 24px;
}

details {
  border-top: 1px solid var(--line);
  padding: 20px 0;
}

details:first-of-type {
  border-top: 0;
  padding-top: 0;
}

summary {
  cursor: pointer;
  font-weight: 700;
  font-size: 16px;
  list-style: none;
  padding-right: 28px;
  position: relative;
}

summary::-webkit-details-marker {
  display: none;
}

summary::after {
  content: "+";
  position: absolute;
  right: 0;
  top: -2px;
  color: var(--accent-2);
  font-size: 22px;
  font-weight: 400;
  line-height: 1;
}

details[open] summary::after {
  content: "−";
}

details p,
details ul {
  margin: 12px 0 0;
  color: var(--muted);
}

details ul {
  padding-left: 20px;
}

details li + li {
  margin-top: 6px;
}

.policy p,
.policy li {
  color: var(--muted);
}

.policy ul {
  padding-left: 22px;
}

.policy li + li {
  margin-top: 6px;
}

.policy h2 {
  margin-top: 34px;
}

.policy h2:first-of-type {
  margin-top: 0;
}

.policy .summary-box {
  background: var(--surface-soft);
  border-radius: 14px;
  padding: 18px 20px;
  margin-bottom: 8px;
}

.policy .summary-box p {
  margin: 0 0 6px;
}

.site-footer {
  max-width: 860px;
  margin: 0 auto;
  padding: 22px 20px 40px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 14px;
}

.site-footer p {
  margin: 6px 0;
}

@media (max-width: 620px) {
  .site-header {
    align-items: flex-start;
    flex-direction: column;
    gap: 12px;
  }

  .site-nav {
    flex-wrap: wrap;
    gap: 14px;
  }

  .hero {
    padding-top: 28px;
  }

  .app-mark {
    width: 92px;
    height: 92px;
    border-radius: 22px;
  }

  .panel {
    padding: 22px 18px;
    border-radius: 16px;
  }
}

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

  .btn {
    transition: none;
  }
}