:root {
  color-scheme: light dark;
  --bg: #ffffff;
  --text: #000000;
  --muted: #6b6b6b;
  --line: #e5e5e5;
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Helvetica Neue", Helvetica, Arial, sans-serif;
}

html[lang^="zh"] {
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #000000;
    --text: #ffffff;
    --muted: #9a9a9a;
    --line: #2a2a2a;
  }
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-size: 16px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; text-underline-offset: 3px; }

a:focus-visible,
summary:focus-visible {
  outline: 2px solid var(--text);
  outline-offset: 4px;
}

.wrap { max-width: 680px; margin-inline: auto; padding-inline: 20px; }

.skip-link {
  position: absolute;
  top: -100px;
  left: 16px;
  padding: 8px 14px;
  background: var(--bg);
  border: 1px solid var(--text);
  z-index: 1;
}
.skip-link:focus { top: 12px; }

.header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 16px;
  padding-top: 64px;
}

.brand { font-size: 0.95rem; font-weight: 600; letter-spacing: 0.02em; }
.header-label { color: var(--muted); font-size: 0.9rem; }

main { padding-block: 48px 64px; }

h1 {
  margin: 0 0 12px;
  font-size: 2.25rem;
  font-weight: 700;
  line-height: 1.15;
  letter-spacing: -0.02em;
}

html[lang^="zh"] h1 { line-height: 1.3; letter-spacing: 0; }

.intro { margin: 0 0 8px; }
.platforms { margin: 0; color: var(--muted); font-size: 0.9rem; }

.contact {
  margin-top: 40px;
  padding: 24px 0;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}
.contact h2 { margin: 0 0 4px; }
.contact p { margin: 0; color: var(--muted); }
.contact .hint { font-size: 0.9rem; }

.email {
  display: inline-block;
  min-height: 44px;
  margin-block: 12px;
  padding-block: 4px;
  font-size: 1.4rem;
  font-weight: 600;
  overflow-wrap: anywhere;
}

.section { padding-top: 40px; }

h2 {
  margin: 0 0 12px;
  font-size: 1.2rem;
  font-weight: 650;
  line-height: 1.3;
}

p { margin: 0 0 14px; }

.section-intro { color: var(--muted); }

.checklist { margin: 16px 0 0; padding-left: 1.4rem; }
.checklist li { margin: 0 0 14px; }
.checklist strong { display: block; }
.checklist p { margin: 0; color: var(--muted); }

details { border-top: 1px solid var(--line); }
details:last-child { border-bottom: 1px solid var(--line); }

summary {
  min-height: 44px;
  padding: 14px 0;
  cursor: pointer;
  font-weight: 600;
}

details p { padding-bottom: 6px; color: var(--muted); }

footer {
  padding-block: 24px 48px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 0.88rem;
}

footer p { margin: 0 0 8px; }
footer nav { display: flex; flex-wrap: wrap; gap: 0 18px; }
footer a { display: inline-flex; align-items: center; min-height: 44px; color: var(--muted); }

@media (max-width: 520px) {
  .wrap { padding-inline: 16px; }
  .header { padding-top: 40px; }
  main { padding-top: 32px; }
  h1 { font-size: 1.85rem; }
}