.rdio {
  border-radius: 50%;
  border-style: solid;
  border-width: .0625rem;
  box-sizing: border-box;
  display: inline-block;
  position: relative;
  width: 1rem;
  height: 1rem;
  transition: none;
}

.rdio::before,
.rdio::after {
  border-radius: 50%;
  border-style: solid;
  border-width: 0;
  box-sizing: content-box;
  content: "";
  left: 50%;
  position: absolute;
  top: 50%;
  transform: translate(-50%, -50%);
  transition: inherit;
}

.rdio:checked::after {
  border-width: .25rem;
}