<!DOCTYPE html>
<html>
<head>
</head>
<body>
  <div></div>
</body>
</html>
div {
      width: 100px;
      height: 100px;
      background: orange;
      transition: all 2s;
    }
    div:hover {
      border-radius: 50%;
      background: skyblue;
    }

External CSS

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External JavaScript

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