JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
<div class="block first">
<h1>Our Cool Heading</h1>
</div>
<div class="block second">
<p>small text</p>
</div>
</div>

CSS

.container {
  aspect-ratio: 2 / 1;
  width: 400px;
  display: flex;
  color: white;
}

.first {
  width: 50%;
  background-color: blue;
}

.second {
  background-color: red;
  flex-grow: 1
}

.withsystemtextsize {
  font-size: 1.75rem;
}

.withmediaquery {
  flex-direction: column;
  aspect-ratio: auto;
}

.withmediaquery .first {
  width: 100%
}