How to get Fade-in-out modal effect?

https://jsfiddle.net/7doq0vkL/1/

I'm trying to get this JSFiddle to fade-in and fade out on close. It's working but after closing it hasn't been opening again. I tried to set the div to display:none after 900ms but that stopped the close fade working. Can anyone see what change to JSFiddle would need to be made to allow it to open again?

<div class="w3-container">
  <h2>Animated Modal</h2>

  <button onclick="document.getElementById('id01').style.display='block'" class="w3-button w3-black">Fade In Modal</button>

  <div id="id01" class="w3-modal w3-animate-opacity">
    <div class="w3-modal-content w3-card-4">
      <header class="w3-container w3-teal">
        <span onclick="document.getElementById('id01').classList.add('w3-animate-show');" class="w3-button w3-large w3-display-topright">&times;</span>
        <h2>Modal Header</h2>
      </header>
      <div class="w3-container">
        <p>Some text..</p>
        <p>Some text..</p>
      </div>
      <footer class="w3-container w3-teal">
        <p>Modal Footer</p>
      </footer>
    </div>
  </div>
</div>

CSS

 .w3-animate-opacity {
   animation: opac 0.8s
 }

 @keyframes opac {
   from {
     opacity: 0
   }
   to {
     opacity: 1
   }
 }

 .w3-animate-show {
   animation: show 0.8s;
   animation-fill-mode: forwards;
 }

 @keyframes show {
   0% {
     opacity: 1
   }
   100% {
     opacity: 0
   }
 }