:root {
  --bg1: #f7f6ff;
  --bg2: #edf3ff;
  --card: rgba(255, 255, 255, 0.96);
  --text: #1d2433;
  --muted: #4f5977;
  --accent: #2f67f3;
  --accent-soft: #eaf1ff;
  --line: #dbe3f6;
}

* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: "Segoe UI", "Trebuchet MS", sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at 12% 12%, #ffd5e5 0%, transparent 30%),
    radial-gradient(circle at 80% 0%, #d4f0ff 0%, transparent 28%),
    linear-gradient(140deg, var(--bg1), var(--bg2));
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: 32px 16px;
}

.page-shell {
  width: min(980px, 100%);
  display: grid;
  gap: 18px;
}

.site-header, .card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 18px;
  box-shadow: 0 8px 28px rgba(30, 40, 71, 0.09);
}

.site-header {
  text-align: center;
  padding: 24px;
}

.eyebrow {
  margin: 0;
  color: var(--accent);
  font-weight: 600;
  letter-spacing: .06em;
  text-transform: uppercase;
}

h1, h2 { margin-top: .3em; margin-bottom: .3em; }
.subtitle { margin: 0 0 16px; color: var(--muted); }

nav { display: flex; justify-content: center; flex-wrap: wrap; gap: 10px; }

.btn {
  text-decoration: none;
  color: var(--accent);
  border: 1px solid var(--line);
  background: #fff;
  border-radius: 999px;
  padding: 10px 16px;
  font-weight: 600;
  transition: transform .15s ease, box-shadow .15s ease;
}

.btn:hover { box-shadow: 0 6px 14px rgba(47, 103, 243, 0.24); transform: translateY(-1px); }
.btn--active { background: var(--accent); color: #fff; }

main { display: grid; gap: 16px; }
.card { padding: 20px; }
.card ul, .card ol { margin-bottom: 0; }
.card--accent { background: var(--accent-soft); border-color: #bad1ff; }

footer { margin-top: 4px; text-align: center; color: var(--muted); }
code { background: #f2f4fd; border: 1px solid #d5e1ff; border-radius: 6px; padding: 2px 6px; font-size: .95em; }

@media (max-width: 640px) {
  body { padding: 16px 10px; }
  .site-header, .card { padding: 16px; }
}