強制置中

//  置中
@mixin both-center {
    display: -webkit-box;
    display: -ms-flexbox;
    display: -webkit-flex;
    display: flex;
    -webkit-box-pack: center;
    -ms-flex-pack: center;
    -webkit-justify-content: center;
    justify-content: center;
    -webkit-box-align: center;
    -ms-flex-align: center;
    -webkit-align-items: center;
    align-items: center;
}