body {
  background-color: #aaaaaa;
  padding-left: calc(50vw - 100px);
  padding-top: calc(50vh - 100px);
}

a {
  position: relative;
  top: 0px;
  left: 0px;

  display: block;
  width: 200px;
  height: 200px;
  border-radius: 50px;

  font-size: 32px;
  font-weight: bold;
  user-select: none;

  text-align: center;
  line-height: 200px;

  box-shadow:
    6px 8px 20px #000000,
    -6px -8px 20px #ffffff,
    inset -3px -4px 20px #00000066,
    inset 3px 4px 20px #ffffff66;
  transition: all 0.2s cubic-bezier(0.23, 1, 0.32, 1);
}

a:active {
  position: relative;
  top: 6px;
  left: 3px;

  background-color: #999999;
  box-shadow:
    -6px -8px 20px #000000,
    6px 8px 20px #ffffff,
    inset 3px 4px 10px #000000,
    inset -3px -4px 20px #ffffff66;
}