text: goog.require('ol.Map');
  goog.require('ol.View');
  goog.require('ol.format.KML');
  goog.require('ol.layer.Heatmap');
  goog.require('ol.layer.Tile');
  goog.require('ol.source.Stamen');
  goog.require('ol.source.Vector');
  
  var blur = document.getElementById('blur');
  var radius = document.getElementById('radius');
  
  var vector = new ol.layer.Heatmap({
    source: new ol.source.Vector({
      url: 'data/kml/2012_Earthquakes_Mag5.kml',
      format: new ol.format.KML({
        extractStyles: false
      })
    }),
    blur: parseInt(blur.value, 10),
    radius: parseInt(radius.value, 10)
  });
  
  vector.getSource().on('addfeature', function(event) {
    // 2012_Earthquakes_Mag5.kml stores the magnitude of each earthquake in a
    // standards-violating <magnitude> tag in each Placemark.  We extract it from
    // the Placemark's name instead.
    var name = event.feature.get('name');
    var magnitude = parseFloat(name.substr(2));
    event.feature.set('weight', magnitude - 5);
  });
  
  var raster = new ol.layer.Tile({
    source: new ol.source.Stamen({
      layer: 'toner'
    })
  });
  
  var map = new ol.Map({
    layers: [raster, vector],
    target: 'map',
    view: new ol.View({
      center: [0, 0],
      zoom: 2
    })
  });
  
  
  blur.addEventListener('input', function() {
    vector.setBlur(parseInt(blur.value, 10));
  });
  
  radius.addEventListener('input', function() {
    vector.setRadius(parseInt(radius.value, 10));
  });
  