<li>Details &amp; Summary behave a lot like the <a href="https://codepen.io/collection/EdGoh/">accordion design pattern</a>, only just the basics. Could you layer on functionality, like a group of details elements in which only one can be open at once?</li>
  <li>Can you progressively enhance Details &amp; Summary to add custom styling and animation?</li>
  <li>These elements <a href="https://caniuse.com/#feat=details">don't work in Edge</a>. You could have a look at the polyfills out there and perhaps build your own if you'd like to have a go at it.</li>
@import url("https://fonts.googleapis.com/css?family=Lato:400,400i,700");
ol {
  max-width: 350px;
  counter-reset: my-awesome-counter;
  list-style: none;
  padding-left: 40px;
ol li {
  margin: 0 0 0.5rem 0;
  counter-increment: my-awesome-counter;
  position: relative;
ol li::before {
  content: counter(my-awesome-counter);
  color: #fcd000;
  font-size: 1.5rem;
  font-weight: bold;
  position: absolute;
  --size: 32px;
  left: calc(-1 * var(--size) - 10px);
  line-height: var(--size);
  width: var(--size);
  height: var(--size);
  top: 0;
  transform: rotate(-10deg);
  background: black;
  border-radius: 50%;
  text-align: center;
  box-shadow: 1px 1px 0 #999;

body {
  background: #191919;
  color: #eee;
  font-family: Lato, sans-serif;
  line-height: 1.4;
  font-size: 90%;
  margin: 2rem;

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

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