JSFiddle - React, Tailwind, and code Playground

by brigand

HTML

<div class="box">
  <div>
    Hover me
  </div>
  <div class="button">Click me</div>
</div>

CSS

:root {
  --btn-color: #c9c9c9;
  --btn-color-hover: #6699ff;
}

.box {
  display: flex;
  padding: 1em;
}

.box > :first-child {
  flex: 1 1 auto;
}

.button {
  padding: 1em 3em;
  background: var(--btn-color);
}

.box:hover {
  --btn-color: var(--btn-color-hover);
}