@charset "utf-8";
  <style>
    body {
      margin: 0;
	  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen", "Ubuntu", "Cantarell", "Fira Sans", "Droid Sans", "Helvetica Neue", "メイリオ", Meiryo, sans-serif;

      background-color: #f8f8f8;
      color: #333;
      line-height: 1.6;
    }

    header {
      background-color: #4CAF50;
      color: white;
      padding: 1rem 1.25rem;
      display: flex;
      justify-content: space-between;
      align-items: center;
      position: sticky;
      top: 0;
      z-index: 1000;
      box-shadow: 0 2px 5px rgba(0,0,0,0.2);
      border-bottom-left-radius: 8px;
      border-bottom-right-radius: 8px;
    }

    .site-title {
      font-size: 1.5rem;
      margin: 0;
      white-space: nowrap;
    }

    .nav-toggle {
      display: block;
      background: none;
      border: none;
      font-size: 2rem;
      color: white;
      cursor: pointer;
    }

    nav.nav-menu {
      position: absolute;
      top: 100%;
      left: 0;
      width: 100%;
      background-color: #333;
      overflow: hidden;
      max-height: 0;
      transition: max-height 0.3s ease;
    }

    body.nav-active nav.nav-menu {
      max-height: 500px;
    }

    nav.nav-menu ul {
      display: flex;
      flex-direction: column;
      margin: 0;
      padding: 0;
      list-style: none;
    }

    nav.nav-menu li {
      border-bottom: 1px solid #555;
    }

    nav.nav-menu li:last-child {
      border-bottom: none;
    }

    nav.nav-menu a {
      display: block;
      padding: 1rem;
      color: white;
      text-decoration: none;
      text-align: center;
      transition: background-color 0.3s ease;
    }

    nav.nav-menu a:hover,
    nav.nav-menu a:focus {
      background-color: #555;
    }

    .container {
      max-width: 960px;
      margin: 0 auto;
      padding: 1.25rem;
    }

    .adsense-placeholder {
      background-color: #e0e0e0;
      color: #666;
      text-align: center;
      padding: 1rem;
      margin: 1.25rem auto;
      max-width: 960px;
      border: 1px dashed #aaa;
      border-radius: 8px;
      font-size: 0.9rem;
    }

    .content-block {
      margin-bottom: 2rem;
    }

    .content-block img {
      max-width: 100%;
      height: auto;
      border-radius: 8px;
      box-shadow: 0 2px 5px rgba(0,0,0,0.1);
      margin-bottom: 1rem;
    }

    @media (max-width: 480px) {
      .container {
        padding: 1rem;
      }
    }

    @media (min-width: 768px) {
      .nav-toggle {
        display: none;
      }

      nav.nav-menu {
        position: static;
        background-color: transparent;
        max-height: none;
        overflow: visible;
        transition: none;
      }

      nav.nav-menu ul {
        flex-direction: row;
        justify-content: flex-end;
      }

      nav.nav-menu li {
        border-bottom: none;
        margin-left: 1rem;
      }

      nav.nav-menu a {
        padding: 0.5rem 0.75rem;
        border-radius: 4px;
      }

      nav.nav-menu a:hover,
      nav.nav-menu a:focus {
        background-color: rgba(255, 255, 255, 0.2);
      }

      .content-block {
        display: flex;
        align-items: flex-start;
        gap: 1.5rem;
      }

      .content-block img {
        width: 300px;
        margin-bottom: 0;
        flex-shrink: 0;
      }

      .content-block p {
        margin: 0;
        flex: 1;
      }
    }
  </style>