wagtail/client/scss/layouts/_focal-point-chooser.scss

.focal-point-chooser {
  position: relative;
  margin-bottom: 20px;

  .current-focal-point-indicator {
    @include transition(opacity 0.2s ease);
    box-shadow: 1px 1px 10px 0 theme('colors.black-50');
    position: absolute;
    border: 3px solid theme('colors.border-button-outline-default');
    opacity: 0.7;

    &.hidden {
      display: none;
    }
  }

  &:hover .current-focal-point-indicator {
    opacity: 0;
  }
}