<section class="accordion">
  <div class="tab">
    <input type="checkbox" name="accordion-1" id="cb1" checked>
    <label for="cb1" class="tab__label">Checkbox</label>
    <div class="tab__content">
      <p>Pure CSS accordion based on the "input:checked + label" style trick.</p>
    </div>
  </div>
  <div class="tab">
    <input type="checkbox" name="accordion-1" id="cb2">
    <label for="cb2" class="tab__label">Open multiple</label>
    <div class="tab__content">
      <p>Using <code>&lt;input type="checkbox"&gt;</code> allows to have several tabs open at the same time.</p>
    </div>
  </div>
</section>

<section class="accordion accordion--radio">
  <div class="tab">
    <input type="radio" name="accordion-2" id="rd1">
    <label for="rd1" class="tab__label">Radio</label>
    <div class="tab__content">
      <p>If you want to have only one tab open, you can use <code>&lt;input type="checkbox"&gt;</code>.</p>
    </div>
  </div>
  <div class="tab">
    <input type="radio" name="accordion-2" id="rd2">
    <label for="rd2" class="tab__label">Open single</label>
    <div class="tab__content">
      <p>But if you wanna close the opened tab, you must add a "close" button somewhere, like the one below, that is just another styled radio input.</p>
    </div>
  </div>
  <div class="tab">
    <input type="radio" name="accordion-2" id="rd3">
    <label for="rd3" class="tab__close">Close open tab &times;</label>
  </div>
</section>
:root {
  --primary: #227093;
  --secondary: #ff5252;
  --background: #eee;
  --highlight: #ffda79;
  /* Theme color */
  --theme: var(--primary);
}
*, *::before, *::after {
  box-sizing: border-box;
}
body {
  display: grid;
  place-content: center;
  grid-template-columns: repeat(auto-fit, min(100%, 30rem));
  min-height: 100vh;
  place-items: start;
  gap: 1rem;
  margin: 0;
  padding: 1rem;
  color: var(--primary);
  background: var(--background);
}

/* Core styles/functionality */
.tab input {
  position: absolute;
  opacity: 0;
  z-index: -1;
}
.tab__content {
  max-height: 0;
  overflow: hidden;
  transition: all 0.35s;
}
.tab input:checked ~ .tab__content {
  max-height: 10rem;
}

/* Visual styles */
.accordion {
  color: var(--theme);
  border: 2px solid;
  border-radius: 0.5rem;
  overflow: hidden;
}
.tab__label,
.tab__close {
  display: flex;
  color: white;
  background: var(--theme);
  cursor: pointer;
}
.tab__label {
  justify-content: space-between;
  padding: 1rem;
}
.tab__label::after {
  content: "\276F";
  width: 1em;
  height: 1em;
  text-align: center;
  transform: rotate(90deg);
  transition: all 0.35s;
}
.tab input:checked + .tab__label::after {
  transform: rotate(270deg);
}
.tab__content p {
  margin: 0;
  padding: 1rem;
}
.tab__close {
  justify-content: flex-end;
  padding: 0.5rem 1rem;
  font-size: 0.75rem;
}
.accordion--radio {
  --theme: var(--secondary);
}

/* Arrow animation */
.tab input:not(:checked) + .tab__label:hover::after {
  animation: bounce .5s infinite;
}
@keyframes bounce {
  25% {
    transform: rotate(90deg) translate(.25rem);
  }
  75% {
    transform: rotate(90deg) translate(-.25rem);
  }
}

External CSS

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