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                <header class="header">
  <div class="header__title">
  <div class="header__reference">
    <ul class="reference-list">
      <li><a class="reference-list__link" href="">MDN reference</a></li>
      <li><a class="reference-list__link" href="">caniuse Support</a></li>

  <div class="example">
      In this example, you can toggle the removal of a grayscale effect, bringing <a href="">the magic of Technicolor</a> to the land of Oz: 

      Toggle grayscale
    <div class="example__demo example__demo--grayscale">
        alt="Dorothy, The Cowardly Lion, The Tin Man, and Scarecrow walking down the Yellow Brick Road. The city of Oz is visible on the horizon." 
        src="" />



                // Demo
.js-remove-grayscale {
  filter: grayscale(0) !important; // Forces immutability

.yellow-brick-road {
  filter: grayscale(1);
  transition: filter var(--transition-duration-longer) ease-in-out;

// Pen Setup
.example__demo--grayscale {
  padding: 0.5rem;

.yellow-brick-road {
  display: block;
  height: auto;
  width: 100%;


                const button = document.querySelector('button');

function toggleGrayscale() {
  var yellowBrickRoad = document.querySelector('.yellow-brick-road');

button.addEventListener('click', toggleGrayscale);

button.addEventListener('click', event => {
  if (button.getAttribute('aria-pressed') === "false") {
    button.setAttribute('aria-pressed', 'true');
  else {
    button.setAttribute('aria-pressed', 'false');