body {
	font-family: sans-serif;
}

#map {
	height: 100vh;
}

.cluster-div {
  background-color: transparent;
  height: 3rem;
  width: 3rem;
  border-radius: 50%;
  box-shadow:
    0 0 0 4px white,   /* white ring */
    0 0 20px 10px black;    /* black glow */

  transform: translate(-50%, -50%);
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 1.5rem;
  font-weight: bold;

  text-shadow:
    -2px -2px 0 black,
     2px -2px 0 black,
    -2px  2px 0 black,
     2px  2px 0 black,
     0   -2px 0 black,
     0    2px 0 black,
    -2px  0    0 black,
     2px  0    0 black;
}