scss : div水平垂直居中

@mixin absolute_center_mixin($width, $height){
    position: absolute;
    top: 50%;
    left: 50%;
    margin-left: -($width / 2);
    margin-top: -($height / 2);
    width: $width;
    height: $height;
    background: #000;
}

html{
    body{
        .main{            
            .left{
                position: relative;
                .box{
                    @include absolute_center_mixin(3.106297rem, 1.405564rem);
                }
            }
        }        
    }
}