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  <h1>Pure CSS pop-up (modal) 
    with &lt;details&gt; and &lt;summary&gt;</h1>
  <p>The native HTML elements that open and close without any scripts can be used for FAQs, but also for modals!</p>
    <summary class="button">Click to open me</summary>
      <h2>Everything after summary appears within a modal</h2>
      <p>The HTML Details Element creates a disclosure widget in which information is visible only when the widget is toggled into an "open" state. A summary or label can be provided using the summary element.</p>



                body { 
  padding: 2em 4em;
  font-family: Roboto, sans-serif;

.button {
  width: 10em;
  text-align: center;
  font-weight: bold;
  padding: 1em 2em;
  background: DEEPPINK;
  border-radius: 3em;
  color: white;
  cursor: pointer;

details > div {
  width: 20em;
  border: 2px solid black;
  padding: 1em 2em;
  position: fixed;
  width: 360px;
  height: 240px;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  margin: auto;
  background: white;
  z-index: 3;
  box-shadow: 10px 10px 10px DIMGRAY;

details[open] summary::after { 
  content: "×"; 
  font-size: 28pt;  
  position: fixed; 
  right: calc(50vw - 360px / 2 - 2em); 
  top:  calc(50vh - 240px / 2 - 2em);
  padding: 5pt 10pt;
  z-index: 9;

details[open] summary::before {
  content: '';
  display: block;
  width: 100vw;
  height: 100vh;
  background: black;
  position: fixed;
  top: 0;
  left: 0;
  opacity: 0.5;
  z-index: 1;