body {
    font-family: 'Inter', sans-serif;
    background-color: #f0f2f5;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    padding: 20px 0;
    box-sizing: border-box;
    overflow-y: auto;
  }

  .course-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: #333;
    text-align: center;
    margin-bottom: 20px;
    padding: 10px 0;
    text-decoration: underline;
  }

  .card-item {
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    cursor: pointer;
    display: flex;
    flex-direction: column;
    transition: transform 0.2s ease-in-out;
    height: 192px;
    margin-bottom: 1.0rem;
    /* Bootstrapのrow-colsに影響されないように余白を追加 */
  }

  .card-item:hover {
    transform: translateY(-5px);
  }

  .card-image-thumbnail {
    width: 100%;
    height: 152px;
    object-fit: cover;
    border-top-left-radius: 10px;
    border-top-right-radius: 10px;
  }

  .card-title-thumbnail {
    padding: 10px;
    font-size: 1rem;
    font-weight: 600;
    color: #333;
    text-align: center;
    flex-grow: 1;
    display: flex;
    align-items: center;
    justify-content: center;
  }

  /* ポップアップ画面の幅を元の画面幅に対応するように調整 */
  .modal-dialog {
    /* Bootstrapのmodal-xlクラスが設定するmax-widthを上書き */
    max-width: 1024px !important;
    /* !important を付けて強制的に適用 */
    width: 90%;
    /* ビューポートの90%の幅、ただしmax-widthを超えない */
    margin: 1.75rem auto;
    /* Bootstrapのデフォルトマージンを維持しつつ中央寄せ */
    height: 90vh;
    /* 高さを画面の90%に維持 */
  }

  .modal-content {
    height: 100%;
    /* 親要素 (modal-dialog) の高さに合わせる */
    display: flex;
    flex-direction: column;
    border-radius: 5px;
    /* 角の丸みを5pxに戻す */
  }

  .modal-body {
    flex-grow: 1;
    overflow-y: auto;
    padding: 1rem !important;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
  }

  .close-button {
    position: absolute;
    top: 15px;
    right: 15px;
    z-index: 1001;
    background-color: rgba(0, 0, 0, 0.5);
    color: white;
    border-radius: 50%;
    width: 30px;
    height: 30px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.5rem;
    cursor: pointer;
    opacity: 0.5;
  }