anchor.diff:  
   
   map.on('click', function(event) {
  +  var popup = new mapboxgl.Popup({offset: 25})
  +    .setText('Construction on the Washington Monument began in 1848.');
  +
     var el = document.createElement('div');
     var marker = new mapboxgl.Marker(el)
     .setLngLat(event.lngLat)
  
positive.code:    });
  });
  
  
  </script> <!-- end of base map -->
  
  
negative.code:     layout: {
        "icon-image": "star-15",
        "icon-allow-overlap": true
      }
    })
  
    map.getSource('pins').setData({
  