#chart_div {
  width: 100%;
  height: 540px;
  background: #ddd;
}

text {
  pointer-events: none;
}

.grandparent text {
  font-weight: bold;
}

rect {
  /*fill: none;*/
  stroke: #fff;
}

rect.parent,
.grandparent rect {
  stroke-width: 2px;
}

.grandparent rect {
  fill: green;
}

.grandparent:hover rect {
  fill: lightgreen;
}

.children rect.parent,
.grandparent rect {
  cursor: pointer;
}

.children rect.parent {
  /*fill: #bbb;*/
  fill-opacity: .5;
}

.children:hover rect.child {
  /*fill: #bbb;*/
}