<div></div>
div {
  inline-size: 20px;
  block-size: 20px;
  margin: 50px;

  background: #000;
  border-radius: 50%;
}

div:hover {
  box-shadow: 
  0 0 0 3px #ffffff,
  0 0 0 5px #000000;
}

External CSS

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External JavaScript

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