//处理动画
@mixin tr($time,$type) {
    transition: $type $time;
}
//响应式宽度判断
@mixin max-screen($res) {
    @media (max-width: $res) {
        @content;
    }
}
//响应式高度判断
@mixin maxh-screen($res) {
    @media (max-height: $res) {
        @content;
    }
}