:root {
  --bg: #f4f7fb;
  --panel: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --primary: #0f4c81;
  --primary-soft: #e8f1fb;
  --border: #d8e0ea;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at 10% 0%, #dbeafe 0, transparent 35%),
    radial-gradient(circle at 90% 10%, #e0f2fe 0, transparent 30%),
    var(--bg);
}

.container {
  max-width: 920px;
  margin: 0 auto;
  padding: 28px 16px 56px;
}

.card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 16px;
  box-shadow: 0 8px 28px rgba(15, 76, 129, 0.08);
  padding: 24px;
}

header h1 {
  margin: 0;
  font-size: 30px;
  letter-spacing: 0.4px;
}

.sub {
  margin-top: 8px;
  color: var(--muted);
  font-size: 14px;
}

nav {
  margin-top: 18px;
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

a.btn {
  text-decoration: none;
  border: 1px solid var(--border);
  color: var(--text);
  background: #fff;
  border-radius: 999px;
  padding: 8px 14px;
  font-size: 14px;
}

a.btn.active,
a.btn:hover {
  background: var(--primary-soft);
  border-color: #bfd5ee;
  color: var(--primary);
}

main {
  margin-top: 18px;
}

h2 {
  margin: 20px 0 10px;
  color: var(--primary);
  font-size: 20px;
}

p, li {
  line-height: 1.7;
  font-size: 15px;
}

ul {
  padding-left: 20px;
  margin: 8px 0;
}

.note {
  margin-top: 10px;
  border-left: 4px solid #93c5fd;
  background: #eff6ff;
  padding: 10px 12px;
  border-radius: 8px;
  color: #1e3a8a;
  font-size: 14px;
}

footer {
  margin-top: 26px;
  color: var(--muted);
  font-size: 13px;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 12px;
  margin-top: 14px;
}

.panel {
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 14px;
  background: #fff;
}

.panel h3 {
  margin: 0 0 6px;
  color: var(--primary);
  font-size: 16px;
}

@media (max-width: 640px) {
  header h1 {
    font-size: 25px;
  }

  .card {
    padding: 18px;
  }
}