body {
    font-family: 'Helvetica Neue', sans-serif;
    margin: 0;
    padding: 0;
    background: #fff;
    color: #333;
  }
  
  .container {
    max-width: 900px;
    margin: 0 auto;
    padding: 20px;
  }
  
  header {
    background: #fff;
    border-bottom: 1px solid #ddd;
  }
  
  .logo {
    font-size: 24px;
    color: #3ba365;
    margin: 10px 0;
  }
  
  nav ul {
    display: flex;
    gap: 20px;
    list-style: none;
    padding-left: 0;
  }
  
  nav a {
    text-decoration: none;
    color: #666;
    font-size: 14px;
  }
  
  .title-section {
    text-align: left;
    padding: 40px 0 10px;
    border-left: 5px solid #a2d9b1;
    padding-left: 16px;
    margin-bottom: 10px;
  }
  
  .title-section h2 {
    font-size: 28px;
    font-weight: bold;
    color: #3a8d58;
    margin: 0;
  }
  
  .title-section .emoji {
    margin-right: 6px;
  }
  
  .subtitle {
    font-size: 13px;
    color: #888;
    margin-top: 5px;
  }
  
  .nav-buttons.tabs-style {
    display: flex;
    gap: 0;
    border-bottom: 2px solid #a2d9b1; /* タブ下のライン */
    margin-bottom: 30px;
  }
  
  .nav-buttons.tabs-style .tab {
    padding: 10px 20px;
    background: #f9fdfb;
    color: #3a8d58;
    text-decoration: none;
    font-weight: 500;
    border: 2px solid #a2d9b1;
    border-bottom: none; /* 下のみなし */
    border-radius: 8px 8px 0 0;
    margin-right: 4px;
    transition: background 0.3s, color 0.3s;
  }
  
  .nav-buttons.tabs-style .tab:hover {
    background: #e3f7eb;
    color: #256c44;
  }
  
  .nav-buttons.tabs-style .tab.active {
    background: #d5f3e2;
    color: #256c44;
    font-weight: bold;
  }
  
  
  .colorful-tabs a {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 10px 18px;
    background: linear-gradient(135deg, #e6f7ec, #c4f1dd);
    border: 1px solid #8dd3a8;
    border-radius: 12px;
    text-decoration: none;
    font-size: 14px;
    color: #256c44;
    font-weight: 500;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
    transition: background 0.3s, transform 0.2s;
  }
  
  .colorful-tabs a:hover {
    background: linear-gradient(135deg, #d7ffeb, #b2f0cf);
    transform: translateY(-2px);
  }

  .tab-content {
    display: none;
  }
  
  .tab-content.active {
    display: block;
  }
  
  
  .guideline-section {
    margin-top: 40px;
  }
  
  .guideline-section h3 {
    font-size: 20px;
    color: #3ba365;
    margin-bottom: 10px;
  }
  
  footer {
    background: linear-gradient(to top, #d0ffe3, #fff);
    text-align: center;
    padding: 30px 0;
  }
  
  .footer-nav {
    list-style: none;
    padding-left: 0;
    display: flex;
    justify-content: center;
    gap: 15px;
    margin-bottom: 10px;
  }
  
  .footer-nav a {
    text-decoration: none;
    color: #555;
    font-size: 13px;
  }
  
  footer p {
    font-size: 12px;
    color: #aaa;
  }