<button class="button">Hover over me ☝️</button>
body {
  display: flex;
  min-height: 100vh;
  justify-content: center;
  align-items: center;
}

.button {
  font-size: 3em;
  font-family: monospace;
  background-color: pink;
  border: 2px solid #000;
  padding: 0.25em 0.5em;
  transition: background-color 2s ease-out;
}

.button:hover {
  background-color: yellow;
}

External CSS

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External JavaScript

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