['mirror', 'happiness', 'freedom', 'minimalism', 'labor']
Necessito un codi HTML per a un botó que, en fer clic, obri una finestra modal amb una imatge que representi la felicitat. L'imatge ha de tenir un alt i ample màxim de 400px i estar centrada a la finestra.
```html
<!DOCTYPE html>
<html>
<head>
<style>
.modal {
  display: none; 
  position: fixed; 
  z-index: 1; 
  left: 0;
  top: 0;
  width: 100%; 
  height: 100%; 
  overflow: auto; 
  background-color: rgb(0,0,0); 
  background-color: rgba(0,0,0,0.4); 
}

.modal-content {
  background-color: #fefefe;
  margin: 15% auto; 
  padding: 20px;
  border: 1px solid #888;
  width: 80%; 
}

.close {
  color: #aaa;
  float: right;
  font-size: 28px;
  font-weight: bold;
}

.close:hover,
.close:focus {
  color: black;
  text-decoration: none;
  cursor: pointer;
}
.modal-image {
  display: block;
  margin-left: auto;
  margin-right: auto;
  max-width: 400px;
  max-height: 400px;
}
</style>
</head>
<body>

<h2>Imatge de Felicitat</h2>

<button id="openModal">Obrir Modal</button>

<div id="myModal" class="modal">

  <div class="modal-content">
    <span class="close">&times;</span>
    <img class="modal-image" src="imatge_de_felicitat.jpg" alt="Felicitat">
  </div>

</div>

<script>
// Get the modal
var modal = document.getElementById("myModal");

// Get the button that opens the modal
var btn = document.getElementById("openModal");

// Get the <span> element that closes the modal
var span = document.getElementsByClassName("close")[0];

// When the user clicks the button, open the modal 
btn.onclick = function() {
  modal.style.display = "block";
}

// When the user clicks on <span> (x), close the modal
span.onclick = function() {
  modal.style.display = "none";
}

// When the user clicks anywhere outside of the modal, close it
window.onclick = function(event) {
  if (event.target == modal) {
    modal.style.display = "none";
  }
}
</script>

</body>
</html>
```