* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Noto Sans JP", "Hiragino Kaku Gothic ProN", sans-serif;
  background-color: #f5f7fa;
  color: #333;
}

/* ヘッダー */
header {
  background: linear-gradient(135deg, #1e3c72, #2a5298);
  color: white;
  text-align: center;
  padding: 40px 15px;
}

header h1 {
  margin: 0;
  font-size: 2rem;
}

header p {
  margin-top: 10px;
  font-size: 1rem;
  opacity: 0.9;
}

/* ナビ */
nav {
  background-color: #1e3c72;
}

nav ul {
  display: flex;
  justify-content: center;
  list-style: none;
  padding: 0;
  margin: 0;
  flex-wrap: wrap;
}

nav li {
  margin: 0 15px;
}

nav a {
  display: block;
  padding: 12px 0;
  color: white;
  text-decoration: none;
  font-weight: bold;
}

nav a:hover {
  color: #a8c8ff;
}

/* メイン */
main {
  max-width: 900px;
  margin: 30px auto;
  padding: 0 15px;
}

section {
  background-color: white;
  padding: 25px;
  margin-bottom: 25px;
  border-radius: 10px;
  box-shadow: 0 5px 10px rgba(0,0,0,0.05);
}

h2 {
  margin-top: 0;
  border-left: 5px solid #2a5298;
  padding-left: 10px;
}

/* フッター */
footer {
  text-align: center;
  padding: 15px;
  background-color: #e0e0e0;
  font-size: 0.9rem;
}

/* スマホ対応 */
@media (max-width: 600px) {
  header h1 {
    font-size: 1.5rem;
  }

  nav li {
    margin: 0 8px;
  }
}