* {
  box-sizing: border-box;
}

:root {
  --bg: #f5f7fb;
  --card: #ffffff;
  --text: #172033;
  --muted: #5c667a;
  --primary: #2563eb;
  --primary-dark: #1e40af;
  --border: #e4e8f0;
}

body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
}

.header {
  background: linear-gradient(135deg, #1e40af, #2563eb);
  color: white;
  padding: 56px 20px;
  text-align: center;
}

.header h1 {
  margin: 0 0 10px;
  font-size: 42px;
}

.header p {
  margin: 0;
  font-size: 18px;
  opacity: 0.95;
}

.nav {
  background: white;
  border-bottom: 1px solid var(--border);
  text-align: center;
  padding: 14px 10px;
  position: sticky;
  top: 0;
}

.nav a {
  display: inline-block;
  color: var(--primary);
  text-decoration: none;
  margin: 6px 12px;
  font-weight: 700;
}

.nav a:hover {
  color: var(--primary-dark);
  text-decoration: underline;
}

.container {
  max-width: 980px;
  margin: 32px auto;
  padding: 0 18px;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 18px;
  padding: 28px;
  box-shadow: 0 10px 25px rgba(20, 35, 70, 0.06);
  margin-bottom: 22px;
}

.grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
}

.feature {
  background: white;
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 22px;
}

.feature h3 {
  margin-top: 0;
  color: var(--primary-dark);
}

h1, h2, h3 {
  line-height: 1.25;
}

h2 {
  margin-top: 32px;
  color: #10204a;
}

ul {
  padding-left: 22px;
}

.notice {
  background: #eef4ff;
  border-left: 5px solid var(--primary);
  padding: 16px 18px;
  border-radius: 12px;
}

.footer {
  text-align: center;
  color: var(--muted);
  padding: 28px 12px 40px;
  font-size: 14px;
}

.button {
  display: inline-block;
  background: var(--primary);
  color: white;
  text-decoration: none;
  padding: 12px 18px;
  border-radius: 999px;
  font-weight: 700;
  margin-top: 12px;
}

.button:hover {
  background: var(--primary-dark);
}

.meta {
  color: var(--muted);
  font-size: 14px;
}

@media (max-width: 760px) {
  .grid {
    grid-template-columns: 1fr;
  }

  .header h1 {
    font-size: 34px;
  }

  .card {
    padding: 22px;
  }
}