body, html {
  background-color: black;
  height: 100%;
  margin:0;
  padding:0;
  overflow: hidden;
}
.emitter {
  background-color: #222;
  position: absolute;
  width: 100px;
  height: 100px;
  border-radius: 50%;
  top: 40%;
  left: 50%;
  border: 2px solid #444;
}
.dot {
  background-color: #4c9a0f;
  border-radius: 50%;
  position: absolute;
  pointer-events: none; /*performance optimization*/
}
#instructions {
  position: fixed;
  top: 10px;
  text-align: center;
  color: #999;
  width: 100%;
  font-family: Arial, sans-serif;
}