[рони]

WhiteFox,
после

<script src="js/scripts.min.js"></script>

добавьте

<script src="https://code.jquery.com/ui/1.10.4/jquery-ui.js"></script>
<script>

      $('.map').draggable(
          {
          drag: function (event, ui) {
              var n = $('.plusnumber').val()/10;
              var h = -$(this).parent().height()/2*n,
              w = -$(this).parent().width()/2*n;  
              ui.position.left > 0 && (ui.position.left = 0);
              ui.position.top > 0 && (ui.position.top = 0);
              ui.position.left < w && (ui.position.left = w+"px");
              ui.position.top < h && (ui.position.top = h+"px");
            }
          }
        )
</script>

и
строка 24

<button class="plus"><input type="text" class="plusnumber" value="0" style="display: none;">+</button>