Hello World

Problem: Clicking button plays audio on desktop, not on mobile

The script tag in head is simply:

          var sound = new Howl({
            src: ['zap.mp3'],
            preload: true
          });
          window.onload = function(){
            var playButton = document.getElementById('play-button');
            playButton.addEventListener('click', function() {
              sound.play();
            })
          }