screen-demo/map-example/cesium/Source/Widgets/SelectionIndicator/SelectionIndicator.css

.cesium-selection-wrapper {
  position: absolute;
  width: 160px;
  height: 160px;
  pointer-events: none;
  visibility: hidden;
  opacity: 0;
  transition: visibility 0s 0.2s, opacity 0.2s ease-in;
}

.cesium-selection-wrapper-visible {
  visibility: visible;
  opacity: 1;
  transition: opacity 0.2s ease-out;
}

.cesium-selection-wrapper svg {
  fill: #2e2;
  stroke: #000;
  stroke-width: 1.1px;
}