.nav-tabs .nav-link.done {
        background-color: rgba(0,200,150,0.4);
        color: #fff;
      }
      .tab-content {
        /* background-color: rgba(255,255,255,0.8); */
        background: linear-gradient(45deg, rgba(255, 255, 255, 0.9), transparent);
        padding: 12px;
        margin-bottom: 12px;
        border-radius: 12px;
      }
      .btn-hint i {
        transition: transform 0.3s ease-in-out;
      }
      .btn-hint[aria-expanded="true"] i {
        transform: rotate(180deg);
      }
      .hint-content {
        background-color: beige;
        border-radius: 12px;
        margin-top: 12px;
        padding: 12px;
      }
      .exercise-btn {
        display: flex;
        align-items: center;
        outline: unset;
        border: unset;
        padding: 0;
        min-height: 36px;
        margin: 4px;
      }
      .exercise-btn:hover span,
      .exercise-btn.active span {
        background-color: #4463b2;
      }
      .exercise-btn span {
        background-color: #718ed8;
        color: white;
        border-radius: 0 6px 6px 0;
        padding: 4px 12px 4px 8px;
        min-height: 36px;
        display: flex;
        align-items: center;
        transition: all .3s ease-in-out;
      }
      .exercise-btn__icon {
        display: flex;
        align-items: center;
        padding: 0 8px;
        height: 36px;
        background-color: #4463b2;
        border-radius: 6px 0 0 6px;
      }
      .exercise-btn__icon img {
        height: 30px;
        width: auto;
      }
      .checklist {
        list-style: none;
        padding-left: 0;
      }
      .checklist li {
        margin-bottom: 6px;
        display: flex;
        align-items: flex-start;
        line-height: 1.4;
      }
      .checklist input[type="checkbox"] {
        margin-right: 8px;
        accent-color: #3fa9f5; /* VS Code blue */
        cursor: pointer;
      }
      .checklist input[type="checkbox"]:checked + label {
        text-decoration: line-through;
        color: #777;
      }
      .checklist label {
        margin-top: -4px;
      }
      code {
        /* background: #1e1e1e; */
        /* color: #ce9178;
        padding: 2px 4px;
        border-radius: 4px; */
      }