message: Bugfix#591: CSS course progress display
  Added responsiveness for mobile devices.
diff: +$min-screen-size: 520px;
  +
  mat-card {
  margin-bottom: 1rem;
  +
  + ngx-charts-advanced-pie-chart > div:first-child {
  + display: flex;
  + height: 100% !important; // !important to override the inline style of the ngx-charts-advanced-pie-chart component. Don't use it in other cases!
  + width: 100% !important;
  +
  + @media screen and (max-width: $min-screen-size) {
  + flex-direction: column;
  + }
  + }
  }
  