Card Stack Shuffle

<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/bundles/anime.umd.min.js"></script>
<script>
  (function () {
    // Card Stack Shuffle: cards sit in a neat stack; the top one swipes away and
    // slides in at the back, revealing the next. Good for testimonials or features.
    // Usage: <div data-card-stack-shuffle> <div>Card 1</div> <div>Card 2</div> … </div>
    // Optional: data-interval (ms between shuffles, default 2600), data-trigger=
    // "click" (shuffle on click instead of on a timer), data-offset (px each card
    // behind peeks out, default 14).
    var DEFAULTS = { interval: 2600, offset: 14 };

    var css =
      '[data-card-stack-shuffle]{display:grid}' +
      '[data-card-stack-shuffle]>*{grid-area:1/1;will-change:transform}';
    var style = document.createElement('style');
    style.textContent = css;
    document.head.appendChild(style);

    function setup(el) {
      var d = el.dataset;
      var cards = Array.from(el.children);
      var offset = +d.offset || DEFAULTS.offset;
      var busy = false;

      function place(card, depth, animate) {
        card.style.zIndex = cards.length - depth;
        var props = {
          y: -depth * offset,
          scale: 1 - depth * 0.06,
          opacity: depth > 2 ? 0 : 1 - depth * 0.15
        };
        if (!animate) return anime.utils.set(card, props);
        props.duration = 700;
        props.ease = 'outBack(1.6)';
        anime.animate(card, props);
      }
      cards.forEach(function (c, i) { place(c, i, false); });

      function shuffle() {
        if (busy || cards.length < 2) return;
        busy = true;
        var top = cards[0];
        anime.animate(top, {
          y: 40, x: 60, rotate: 12, opacity: 0,
          duration: 450,
          ease: 'in(2)',
          onComplete: function () {
            cards.push(cards.shift());
            // Drop it in at the very back, then let everything settle forward.
            place(top, cards.length - 1, false);
            anime.utils.set(top, { x: 0, rotate: 0 });
            cards.forEach(function (c, i) { place(c, i, true); });
            setTimeout(function () { busy = false; }, 350);
          }
        });
      }
      return shuffle;
    }

    function init() {
      var reduced = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
      document.querySelectorAll('[data-card-stack-shuffle]').forEach(function (el) {
        if (el._cs) return;
        var shuffle = (el._cs = setup(el));
        if (reduced) return;
        if (el.dataset.trigger === 'click') {
          el.addEventListener('click', shuffle);
          el.style.cursor = 'pointer';
          return;
        }
        var timer = null;
        new IntersectionObserver(function (entries) {
          entries.forEach(function (e) {
            clearInterval(timer);
            if (e.isIntersecting) timer = setInterval(shuffle, +el.dataset.interval || DEFAULTS.interval);
          });
        }).observe(el);
      });
    }

    if (document.readyState === 'loading') document.addEventListener('DOMContentLoaded', init);
    else init();
  })();
</script>

<div data-card-stack-shuffle>
  <div class="card">“Loved it.”</div>
  <div class="card">“So easy.”</div>
  <div class="card">“Ten out of ten.”</div>
</div>