body{margin:0;background:#111}
#viewer{
  position:relative;
  width:100vw;
  height:100vh;
  overflow:hidden;
}
#viewer svg{
  width:100%;
  height:100%;
}
#lens{
  position:absolute;
  width:120px;
  height:120px;
  border-radius:50%;
  border:2px solid #00f6ff;
  box-shadow:0 0 20px #00f6ff;
  pointer-events:none;
  background-repeat:no-repeat;
  background-size:200% 200%;
  display:none;
}