/* 全体設定 */
body {
  font-family: 'Helvetica Neue', sans-serif;
  background-color: #ffffff;
  color: #222;
  line-height: 1.6;
  margin: 0;
  padding: 0;
}

/* ヘッダー */
header {
  background-color: #f5f5f5;
  padding: 2rem;
  text-align: center;
  border-bottom: 1px solid #ddd;
}

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

.subtitle {
  font-size: 1rem;
  color: #777;
}

/* ナビゲーション */
nav {
  background-color: #ffffff;
  border-bottom: 1px solid #ddd;
}

nav ul {
  display: flex;
  flex-wrap: wrap;
  list-style: none;
  margin: 0;
  padding: 0.5rem 1rem;
  justify-content: center;
}

nav li {
  margin: 0 1rem;
}

nav a {
  text-decoration: none;
  color: #0066cc;
  font-weight: bold;
}

nav a:hover {
  text-decoration: underline;
}

/* セクション */
main {
  padding: 2rem;
  max-width: 960px;
  margin: 0 auto;
}

section {
  margin-bottom: 2rem;
}

h2 {
  border-bottom: 2px solid #ddd;
  padding-bottom: 0.25rem;
}

/* フッター */
footer {
  background-color: #f9f9f9;
  text-align: center;
  padding: 1rem;
  font-size: 0.9rem;
  color: #666;
  border-top: 1px solid #ddd;
}
.navigation-buttons {
  text-align: left;
  margin: 20px 0;
}
.nav-button {
  display: inline-block;
  padding: 8px 16px;
  font-size: 14px;
  background-color: #444;
  color: #fff;
  text-decoration: none;
  border-radius: 6px;
  transition: background-color 0.3s ease;
}
.nav-button:hover {
  background-color: #666;
}