/* js */
(function(){
    var page = $('html, body');

    $('#button-up').click(function() {
      page.animate({scrollTop: 0}, 500);
      return false;
    });

    $(window).scroll(function() {
      if ($(document).scrollTop() > 0) {
        $('#button-up').fadeIn('fast');
      } else {
        $('#button-up').fadeOut('fast');
      }
    });

  })();

/* scss */
#button-up {
	  display: none;
    position: fixed;
    right: 50px;
    bottom: 100px;
    font-size: 0;

    @include MQ(xs) {
    	right: 35px;
    	bottom: 55px;
    }

    &:hover {

    	.button-up__icon {
    		fill: $color-third;
    	}

    }
}

.button-up__icon {
	position: absolute;
	top:50%;
	left: 50%;
	width: 30px;
	height: 30px;
	fill: $color-primary;
	@include drop-shadow(2px 2px 1px black(.15));
	@include center(xy);
	@include transition(all .3s ease);
}

/* pug HTML */
a(href="#")#button-up На верх
	+icon('arrow-up', 'button-up__icon')