body {
}

/*.window {
    width: 450px;
    height: 440px;
    position: absolute;
    text-align: center;
    left: 0;
    right: 0;
    top: 0;
    bottom: 0;
    margin: 100px auto;
    background: #fff;
    z-index: 2000;
}*/

html, body {
    width: 100%;
    height: 100%;
    margin: 0;
    padding: 0;
}

body {
    display: flex;
    align-items: center; /*定义body的元素垂直居中*/
    justify-content: center; /*定义body的里的元素水平居中*/
}

.content {
    width: 400px;
    height: 410px;
    background: white;
}