text: goog.require('ol.Map');
  goog.require('ol.View');
  goog.require('ol.format.KML');
  goog.require('ol.geom.Polygon');
  goog.require('ol.layer.Tile');
  goog.require('ol.layer.Vector');
  goog.require('ol.render');
  goog.require('ol.source.Stamen');
  goog.require('ol.source.Vector');
  goog.require('ol.style.Fill');
  goog.require('ol.style.Icon');
  goog.require('ol.style.Stroke');
  goog.require('ol.style.Style');
  
  
  var symbol = [[0, 0], [4, 2], [6, 0], [10, 5], [6, 3], [4, 5], [0, 0]];
  var scale;
  var scaleFunction = function(coordinate) {
    return [coordinate[0] * scale, coordinate[1] * scale];
  };
  
  var styleCache = {};
  var styleFunction = function(feature) {
    // 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 = feature.get('name');
    var magnitude = parseFloat(name.substr(2));
    var size = parseInt(10 + 40 * (magnitude - 5), 10);
    scale = size / 10;
    var style = styleCache[size];
    if (!style) {
      var canvas =
          /** @type {HTMLCanvasElement} */ (document.createElement('canvas'));
      var vectorContext = ol.render.toContext(
          /** @type {CanvasRenderingContext2D} */ (canvas.getContext('2d')),
          {size: [size, size], pixelRatio: 1});
      vectorContext.setStyle(new ol.style.Style({
        fill: new ol.style.Fill({color: 'rgba(255, 153, 0, 0.4)'}),
        stroke: new ol.style.Stroke({color: 'rgba(255, 204, 0, 0.2)', width: 2})
      }));
      vectorContext.drawGeometry(new ol.geom.Polygon([symbol.map(scaleFunction)]));
      style = new ol.style.Style({
        image: new ol.style.Icon({
          img: canvas,
          imgSize: [size, size],
          rotation: 1.2
        })
      });
      styleCache[size] = style;
    }
    return style;
  };
  
  var vector = new ol.layer.Vector({
    source: new ol.source.Vector({
      url: 'data/kml/2012_Earthquakes_Mag5.kml',
      format: new ol.format.KML({
        extractStyles: false
      })
    }),
    style: styleFunction
  });
  
  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
    })
  });
  