<p class="box">
  <strong>.box:</strong> <br>
  Lorem ipsum dolor sit amet consectetur adipisicing elit. <a href="#">Link</a> fugit, temporibus cupiditate ipsum dicta perferendis voluptate hic voluptatibus eos voluptatum libero quas laboriosam dolore earum commodi vitae. Beatae.
  <br><br>
  <button class="button">
    Button
  </button>
</p>

<p class="box inverted">
 <strong>.box.inverted:</strong> <br>
  Lorem ipsum dolor sit amet consectetur adipisicing elit. <a href="#">Link</a> fugit, temporibus cupiditate ipsum dicta perferendis voluptate hic voluptatibus eos voluptatum libero quas laboriosam dolore earum commodi vitae. Beatae.
  <br><br>
  <button class="button">
    Button
  </button>  
</p>
:root {
  --bg-color: white;  
  --text-color: black;
  --link-color: blue;  
}

a {
  color: var(--link-color);
}

.box {
  color: var(--text-color);
  background: var(--bg-color);
}

.button {
  border-color: var(--link-color);
  color: var(--link-color);
}

.inverted {
  --bg-color: black;
  --text-color: white;
  --link-color: yellow;  
}





/* etc. */
.box {
  display: block;
  border: 1px solid black;
  padding: 1em;
  max-width: 20em;
  display: inline-block;
}

.button {
  appearance: none;
  background: transparent;
  padding: .5em;
}

body {
  margin: 2em;
}

External CSS

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External JavaScript

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