代码片段：
.wrapper {
position: absolute;
top: 50%;
left: 50%;
-webkit-transform: translate(-50%, -50%);
transform: translate(-50%, -50%);
display: -webkit-box;
display: -ms-flexbox;
display: flex;
-webkit-box-pack: center;
-ms-flex-pack: center;
justify-content: center;
width: 100%;
max-width: 500px;
height: 200px;
}
