JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrap">
    <div class="box">三边的box-shadow</div>
</div>

CSS

.wrap{
    width:100px;
    height:200px;
    padding:0 5px 5px 5px;
  
    margin:20px auto;
}
.box{
    box-shadow:0 0 10px rgba(0,0,0,0.4);
    border:1px solid #666;
    border-top:none;
    width:100%;
    height:100%;
}