JSFiddle - React, Tailwind, and code Playground

HTML

<label class="accordion">
  <input type="checkbox" checked>
  <h1>This is the header</h1>
  <div class="accordion-content">
    <p>This is the content of this accordion</p>
  </div>
</label>

CSS

h1
{
  padding: 0.01em;
  margin: 0;
}

h1, p
{
  color: white;
}

.accordion
{
  border-radius: 0.25em;
  background: rgba(0, 0, 0, 0.6);
  display: block;
}

.accordion input[type=checkbox] + :after
{
  content: "\25B6";
  display: inline-block;
  padding-left: 0.5em;
  transition: transform 0.25s;
}

.accordion input[type=checkbox]:checked + :after
{
  transform: rotate(90deg);
}

.accordion input[type=checkbox]
{
  display: none;
  height: 0;
}

.accordion .accordion-content
{
  background: rgba(255,255,255, 0.3);
  height: auto;
  max-height: 0;
  transition: max-height 0.5s;
  overflow: hidden;
  border-radius: 0 0 0.25em 0.25em;
}

.accordion input[type=checkbox]:checked ~ .accordion-content
{
  max-height: 200px;
}