$vari : 1920 / 640;

@function px2rem($size){
	@return $size / 20 / 2 / $vari + rem;
}
@function -px2rem($size){
    @return - $size / 20 / 2 / $vari + rem;
}

.clearfix{
    zoom: 1;
    &::after{
        content: '';
        display: block;
        visibility: hidden;
        height: 0;
        clear: both;
    }
}