JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div class="card">
    <h2>Card title</h2>
  </div>
</div>

CSS

.container {
  container-type: inline-size;
}

.card h2 {
  font-size: 1em;
}

@container (min-width: 500px) {
  .card h2 {
    font-size: 2em;
    color: gray;
  }
}