body, html {
  padding: 0;
  margin: 0;
  height: 100%;
}
svg {
  width: 100%;
  height: 100%;
  background: white;
}

.bubble {
  fill: rgba(0,0,0,0.1);
}
.bubble:hover {
  stroke: black;
  vector-effect: non-scaling-stroke;
}