SOURCE

<div class="sidebar" contenteditable>
  Min: 150px
  <br/>
  Max: 25%
</div>
<p class="content" contenteditable>
  Lorem ipsum dolor sit amet consectetur adipisicing elit. Omnis nulla architecto maxime modi nisi. Quas saepe dolorum, architecto quia fugit nulla! Natus, iure eveniet ex iusto tempora animi quibusdam porro?</p>

body {
  display: grid;
  grid-template-columns: minmax(150px, 25%) 1fr;
  padding: 0;
  margin: 0;
}

.sidebar {
  height: 100vh;
  
  //   etc.
  background: lightpink;
  font-size: 2rem;
  text-align: center;
}

.content {
  padding: 2rem;
}

body {
  font-family: system-ui, serif;
}