覆盖CSS类的动画不起作用

Question

我有以下HTML / CSS / JS。我想在移动设备上或屏幕宽度低于780px的list-div li子级上禁用关键帧动画。因为我不想通过阅读用户代理来弄乱JavaScript解决方案，所以我想到了覆盖已添加的动画类。
但是，这不起作用。所以为什么要覆盖该类并禁用动画是因为我想将li与列表div的角对齐，例如：li:nth-child(1){top: 0; left:0;}通过absolute定位。
这是代码段，我也将其粘贴到屏幕宽度测试的代码笔中：https://codepen.io/anon/pen/JaZgrX

     current = 1;
      $(".list-div ul li").each(function(){
        $(this).addClass("animate").css("animation-delay", current + 's');
        current++;
      });

body {
  margin:0;
}
.container {
  display:flex;
  flex-wrap:wrap;    
  flex-direction:row;    
  height:100vh;
  background-color: beige;
}
.container > div {
  min-height: 100vh;
  border:1px solid black;
  box-sizing:border-box;
  background-color: inherit;
}
.half-width {
  width:50%;
}
.half-width > .half-width-content{
  position: relative;
  margin-top: 0;
  height: 100%;
  width: 100%;
}
.list-div {
  display: flex;
  justify-content: center;
  align-items: center;
}

.list-div ul {
  padding: 0;
  margin-top: 15%;
  width: 75%;
}

.list-div li {
  position: relative;
  display: block;
  border: 1px solid red;
  margin-bottom: 5px;
  padding: 10px;
  text-align: center;
  text-transform: uppercase;
  visibility: hidden;
}

.list-div li.animate{
  visibility: visible;
  animation: fadeIn 1s linear;
  animation-fill-mode: both;
}

@-webkit-keyframes fadeIn {
  0% {
    opacity: 0;
    top: 220px;
  }
  25%{
    opacity: 0.3;
  }
  
  75% {
    opacity: 0.5;
    top: 0px;
  }
  100% {
    opacity: 1;
  }
}

@media max-width:768px{
  
  
  .list-div li.animate{
  visibility: visible;
}
  .list-div {
  display: flex;
  justify-content: center;
  align-items: center;
}
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="container">
<div class="half-width">
    <div class="half-width-content" id="list-cont">
      <div class="list-div">
        <ul>
          <li>Entry A</li>
          <li>Entry B</li>
          <li>Entry C</li>
          <li>Entry D</li>
        </ul>
      </div>
    </div>
  </div>
</div>