:root {
  --bg: #f5f5f7;
  --ink: #1d1d1f;
  --muted: #6e6e73;
  --line: rgba(0, 0, 0, 0.12);
  --blue: #0066cc;
  --page-pad: clamp(1.25rem, 4vw, 2.5rem);
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #000;
    --ink: #f5f5f7;
    --muted: #a1a1a6;
    --line: rgba(255, 255, 255, 0.16);
    --blue: #2997ff;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  font-family: "SF Pro Text", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background:
    radial-gradient(120% 80% at 10% -10%, rgba(0, 102, 204, 0.08), transparent 55%),
    var(--bg);
  color: var(--ink);
  line-height: 1.5;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 10;
  padding: 0.5rem 0.75rem;
  background: var(--ink);
  color: var(--bg);
}

.skip-link:focus {
  left: 0.75rem;
  top: 0.75rem;
}

.top {
  max-width: 40rem;
  margin: 0 auto;
  padding: 1.25rem var(--page-pad) 0;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  color: inherit;
  text-decoration: none;
  font-weight: 600;
  font-size: 0.9375rem;
}

.brand img { display: block; }

.wrap {
  max-width: 40rem;
  margin: 0 auto;
  padding: 2rem var(--page-pad) 3rem;
}

h1 {
  margin: 0 0 0.5rem;
  font-size: clamp(1.75rem, 4vw, 2.25rem);
  letter-spacing: -0.03em;
  line-height: 1.15;
}

.lede {
  margin: 0 0 2rem;
  color: var(--muted);
  font-size: 0.9375rem;
  max-width: 36rem;
}

.lede a,
.wrap a,
.foot a {
  color: var(--blue);
  text-decoration: none;
}

.lede a:hover,
.wrap a:hover,
.foot a:hover {
  text-decoration: underline;
  text-underline-offset: 0.15em;
}

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

h2 {
  margin: 0 0 0.65rem;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  text-transform: none;
  color: var(--muted);
}

ul {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 0.45rem;
}

li {
  font-size: 0.9375rem;
  color: var(--muted);
}

li a {
  font-weight: 500;
  color: var(--ink);
}

.foot {
  max-width: 40rem;
  margin: 0 auto;
  padding: 0 var(--page-pad) max(2rem, env(safe-area-inset-bottom));
  color: var(--muted);
  font-size: 0.75rem;
}

.foot p { margin: 0 0 0.25rem; }