JSFiddle - React, Tailwind, and code Playground

HTML

<button class="button1" onclick="this.classList.toggle('selected')">
  <img src="https://upload.wikimedia.org/wikipedia/commons/9/95/Dunkleosteus_BW.jpg" alt="">
  <img src="https://upload.wikimedia.org/wikipedia/commons/7/7f/Leedsi%26Liopl_DB.jpg" alt="">
</button>

<menu class="toggleMenu">
  <li>Menu Item 1</li>
  <li>Menu Item 2</li>
</menu>

CSS

.button1 img {
  max-height: 100px;
}

.button1:not(.selected) img:first-child {
  display: none;
}

.button1.selected img:last-child {
  display: none;
}

.toggleMenu {
  display: none;
  background-color: silver;
  padding: 10px 30px;
}

.button1.selected ~ .toggleMenu {
  display: block;
}