<p>背景文字背景文字背景文字背景文字</p>
<div>Hover Me</div>
div {
position: absolute;
width: 200px;
height: 60px;
line-height: 60px;
text-align: center;
border: 1px solid #666;
cursor: pointer;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
transition: all .1s;
}
div:hover {
box-shadow: 0 0 0 50vmax rgba(0, 0, 0, .5);
transform: translate(-50%, -60%);
}