JSFiddle - React, Tailwind, and code Playground

HTML

<html>

<head>
  <title>Test</title>
</head>

<body>
 <div class="container">
    <button class="btn">Press</button>
    <div class="ball"></div>
 </div>
</body>

</html>

CSS

.btn {
  width: 100px;
  height: 100px;
  padding: 20px;
  background: red;
  border: 2px solid red;
}

.ball {
  width: 100px;
  height: 100px;
  border-radius: 50px;
  border: 2px solid black;
  background: aquamarine;
  margin: 10px;
}


.btn:hover + .ball {
  transform: scale(2);
}