:root {
  color-scheme: light;
  --ink: #0d2b45;
  --muted: rgba(13, 43, 69, 0.72);
  --line: rgba(13, 43, 69, 0.12);
  --sky: #c8f4ff;
  --mid: #72d6ec;
  --panel: #ffffff;
}
* { box-sizing: border-box; }
html, body { margin: 0; }
body {
  font-family: ui-rounded, "SF Pro Text", system-ui, sans-serif;
  line-height: 1.55;
  color: var(--ink);
  background: linear-gradient(180deg, var(--sky) 0%, var(--mid) 100%);
  min-height: 100vh;
}
main {
  max-width: 40rem;
  margin: 0 auto;
  padding: 2.5rem 1.25rem 4rem;
}
.card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 1.25rem;
  padding: 1.25rem 1.35rem;
  box-shadow: 0 10px 28px rgba(13, 43, 69, 0.12);
}
.hero { text-align: center; margin-bottom: 1.25rem; }
.mark { font-size: 2.4rem; font-weight: 900; letter-spacing: 0.02em; margin: 0; }
.sub { color: var(--muted); margin: 0.35rem 0 0; font-weight: 600; }
h1 { font-size: 1.7rem; margin: 0 0 0.75rem; }
h2 { font-size: 1.05rem; margin: 1.35rem 0 0.4rem; }
p, li { color: var(--ink); }
p.muted, .muted { color: var(--muted); }
ul { padding-left: 1.15rem; }
a { color: #0055b3; }
nav {
  display: flex;
  gap: 1rem;
  justify-content: center;
  margin: 1rem 0 0;
  font-weight: 700;
}
footer {
  margin-top: 1.25rem;
  color: var(--muted);
  font-size: 0.92rem;
}