#selection_overlay {
  position: fixed;
  z-index: 99;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: #999;
}

.selection_box {
  position: absolute;
  z-index: 100;
  border: 1px solid red;
  background-color: blue;
}

.selected_element {
  outline: 1px solid red !important;
  background: yellow !important;
}