.single_post {
    width: 100%;
    margin: 0 auto;
    padding: 40px 0;
  }
  
  .post_detail {
    max-width: 700px; /* ここ修正 */
    width: 90%;
    margin: 0 auto;
  }
  
  .post_thumbnail {
    width: 100%;
    height: auto; /* 固定値から自動に変更 */
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: #f9f9f9;
    overflow: hidden;
    margin-bottom: 20px;
  }
  
  .post_thumbnail img {
    max-width: 100%;
    height: auto;
    object-fit: contain;
    display: block;
  }
  
  .post_title {
    font-size: 2rem;
    margin-bottom: 20px;
    text-align: left;
  }
  
  .post_meta {
    font-size: 0.9rem;
    color: #666;
    margin-bottom: 20px;
    text-align: left;
  }
  
  .post_content {
    font-size: 1rem;
    line-height: 1.8;
  }
  
  @media (max-width: 768px) {
    .post_detail {
      width: 95%;
      padding: 0 10px;
    }
  
    .post_title {
      font-size: 1.5rem;
      text-align: left;
    }
  
    .post_meta {
      font-size: 0.8rem;
      text-align: right;
    }
  
    .post_content {
      font-size: 0.95rem;
      line-height: 1.7;
    }
  
    .post_thumbnail {
      height: 300px;
      width: 100%;
      margin-bottom: 15px;
      object-fit: contain;
      display: block;
    }
  
    .post_thumbnail img {
      max-width: 100%;
      height: auto;
    }
  }