anchor.diff:      if (livedHere == true) {
         properties['lived here'] = true;
         properties['marker-symbol'] = 'building';
  +      properties['marker-size'] = 'medium';
       }
   
       json['geometry'] = geometry;
  
positive.code:     var json = {'type': 'Feature'};
      var geometry = {'type': 'Point',
                      'coordinates': [longitude, latitude]};
      var properties = {'description': name};
  
      if (visitedBy != null) {
        properties['visited by'] = visitedBy.name;
  
negative.code:  * A city that has been visited.
   */
  class City implements Comparable {
    String locality;
    String country;
    double longitude;
  