:root {
  color-scheme: light dark;
  --bg: #f7f8fb;
  --card: #fff;
  --text: #1d2433;
  --muted: #596579;
  --accent: #246bfd;
  --line: #dfe4ec;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
}

header { background: #102a43; color: #fff; }

nav,
main,
footer {
  max-width: 900px;
  margin: auto;
  padding: 20px;
}

nav {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  align-items: center;
}

nav strong { margin-right: auto; }
nav a { color: #fff; }

main {
  padding-top: 36px;
  padding-bottom: 48px;
}

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: clamp(20px, 4vw, 42px);
  box-shadow: 0 8px 28px #0b1f3310;
}

h1 { line-height: 1.15; margin-top: 0; }
h2 { margin-top: 2em; line-height: 1.25; }
a { color: var(--accent); }
.meta,
.note { color: var(--muted); }
.lang { border-top: 2px solid var(--line); margin-top: 48px; padding-top: 24px; }
ul,
ol { padding-left: 22px; }
footer { color: var(--muted); font-size: .92rem; }

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1720;
    --card: #17212d;
    --text: #edf2f7;
    --muted: #b5c0cf;
    --line: #344252;
    --accent: #78a7ff;
  }
}