问无法将模式图像垂直居中

EN

position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%,-50%);

// Get the modal
const modal = document.querySelector(".modal");

// Get the image and insert it inside the modal - use its "alt" text as a caption
const img = document.querySelectorAll(".myImg");
const modalImg = document.querySelector(".img01");


img.forEach((item) => {
  item.onclick = function(e) {
    modal.style.setProperty("display", "flex", "important");
    modalImg.src = e.target.src;
  }
});


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

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

window.onclick = function(event) {
  if (event.target == modal) {
    modal.style.display = 'none';
  }
}

.myImg {
  border-radius: 5px;
  cursor: pointer;
  -webkit-transition: 0.3s;
  -o-transition: 0.3s;
  transition: 0.3s;
}

.myImg:hover {
  opacity: 0.7;
}

.modal {
  display: none;
  position: fixed;
  align-items: center;
justify-content: center;
  z-index: 999;
  padding-top: 35px;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  overflow: auto;
  background-color: rgb(0, 0, 0);
  background-color: rgba(0, 0, 0, 0.9);
}

.center-img{
display: flex;
align-items: center;
justify-content: center;
}
/* Modal Content (image) */

.modal-content {
  margin: auto;
  display: block;
}


/* Add Animation */

.modal-content {
  -webkit-animation-name: zoom;
  -webkit-animation-duration: 0.6s;
  animation-name: zoom;
  animation-duration: 0.6s;
}

@-webkit-keyframes zoom {
  from {
    -webkit-transform: scale(0)
  }
  to {
    -webkit-transform: scale(1)
  }
}

@keyframes zoom {
  from {
    -webkit-transform: scale(0);
    transform: scale(0)
  }
  to {
    -webkit-transform: scale(1);
    transform: scale(1)
  }
}


/* The Close Button */

.close {
  position: absolute;
  top: 15px;
  right: 35px;
  color: #f1f1f1;
  font-size: 40px;
  font-weight: bold;
  -webkit-transition: 0.3s;
  -o-transition: 0.3s;
  transition: 0.3s;
}

.close:hover,
.close:focus {
  color: #bbb;
  text-decoration: none;
  cursor: pointer;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
 <img class="myImg" src="https://lazykcamping.com/assets/Slide-3-Field.jpg" style="width:100%;max-width:500px">



<!-- The Modal -->
<div class="modal">
  <span class="close">&times;</span>
  <img class="modal-content img01">
</div>