.body {
    text-align: center;
    margin: 0 auto;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
}
.body > div {
    position: relative;
    left: 0;
    right: 0;
    margin: 0 auto;
    width: 300px;
    height: 350px;
    margin-top: 100px;
    background-color: #fff;
    border-radius: 10px;
    text-align: center;
    font-size: 20px;
    padding: 10px;
}
.cha {
    font-size: 35px;
    color: #eee;
    position: absolute;
    right: 40px;
    top: 20px;
    cursor: pointer;
}