var raster = new ol.layer.Tile({
  source: new ol.source.TileJSON({
    url: 'https://api.tiles.mapbox.com/v3/mapbox.world-dark.json?secure'
  })
});

var style = new ol.style.Style({
  fill: new ol.style.Fill({
    color: 'rgba(255, 255, 255, 0.6)'
  }),
  stroke: new ol.style.Stroke({
    color: '#319FD3',
    width: 1
  })
});

var vector = new ol.layer.Vector({
  source: new ol.source.Vector({
    url: 'data/topojson/world-110m.json',
    format: new ol.format.TopoJSON(),
    overlaps: false
  }),
  style: function(feature) {
    // don't want to render the full world polygon, which repeats all countries
    return feature.getId() !== undefined ? style : null;
  }
});

var map = new ol.Map({
  layers: [raster, vector],
  target: 'map',
  view: new ol.View({
    center: [0, 0],
    zoom: 1
  })
});
