nodetiles
diff --git a/.gitignore b/.gitignore
@@ -3,6 +3,9 @@
 profile
 
 node_modules
+build
+npm-debug.log
+
 
 # pull these data files down separately (they are HUGE and shouldn't be stored in the repo)
 geodata
diff --git a/.npmignore b/.npmignore
@@ -0,0 +1,8 @@
+# osx noise
+.DS_Store
+profile
+
+node_modules
+
+# pull these data files down separately (they are HUGE and shouldn't be stored in the repo)
+geodata
diff --git a/README.md b/README.md
@@ -70,6 +70,19 @@ map.render({
 
 ```
 
+Magic filtering 
+---------------
+
+To filter objects where a key exists or not, you can use styles with the keyword
+'`$undefined`'
+
+```[myfield='$undefined']```
+
+or
+
+```[myfield!='$undefined']```
+
+
 Thanks
 -------
 
@@ -79,6 +92,22 @@ Projections
 -----------
 [Supported projections](https://github.com/yuletide/node-proj4js-defs)
 
+Developing 
+----------
+
+```
+npx mocha
+```
+
+Common errors
+-------------
+
+If you have issues installing canvas on OS X, you may need to explicitly set the path to pkgconfig:
+
+```
+export PKG_CONFIG_PATH=/opt/X11/lib/pkgconfig
+```
+
 Copyright
 ---------
 Copyright (c) 2012-2014 Code for America. See LICENSE for details.

diff --git a/index.js b/index.js
@@ -21,7 +21,7 @@ module.exports = {
    * Transform between projections
    */
   projector: projector,
-  
+
   /**
    * Routing Middleware
    */

diff --git a/lib/Map.js b/lib/Map.js
@@ -12,7 +12,7 @@ var BUFFER_RATIO = 0.25;
  * map.setStyle(...);
  * map.render(0, 0, 180, 90, 500, 250);
  */
- 
+
 // default to EPSG:3857 (web mercator)
 // http://spatialreference.org/ref/sr-org/7483/
 var DEFAULT_PROJECTION = "EPSG:900913";//"+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs";
@@ -38,7 +38,7 @@ var Map = function(options) {
 
 Map.prototype = {
   constructor: Map,
-  
+
   render: function(options) {
     this._getData(options.bounds, options.boundsBuffer, function(error, shapes) {
       if (error) {
@@ -55,7 +55,7 @@ Map.prototype = {
       }
     }.bind(this));
   },
-  
+
   // Should this really be here, or should it exist on a different object entirely?
   renderGrid: function(options) {//minX, minY, maxX, maxY, width, height, asImage, callback) {
     this._getData(options.bounds, options.boundsBuffer, function(error, shapes) {
@@ -93,11 +93,11 @@ Map.prototype = {
           }
           dataCallback(error, data);
         };
-        
+
         if (typeof datasource !== "function") {
           datasource = datasource.getShapes.bind(datasource);
         }
-        
+
         // allow simple sources to just return results immediately
         var syncData = datasource(dataBounds.minX, dataBounds.minY, dataBounds.maxX, dataBounds.maxY, projection, preCallback);
         if (syncData) {
@@ -131,7 +131,7 @@ Map.prototype = {
       buffer = BUFFER_RATIO;
     }
 
-    amount = (bounds.maxX - bounds.minX) * buffer;
+    var amount = (bounds.maxX - bounds.minX) * buffer;
     return {
       minX: bounds.minX - amount,
       minY: bounds.minY - amount,
@@ -146,15 +146,15 @@ Map.prototype = {
       console.warn("Datasource is not a function or an object with a 'getShapes()' function.");
       return false;
     }
-    
+
     var index = this.datasources.indexOf(datasource);
     if (index === -1) {
       this.datasources.push(datasource);
       return true;
     }
     return false;
   },
-  
+
   removeData: function(datasource) {
     var index = this.datasources.indexOf(datasource);
     if (index > -1) {
@@ -163,12 +163,12 @@ Map.prototype = {
     }
     return false;
   },
-  
+
   setProjection: function(projection) {
     // TODO: validate this somehow?
     this.projection = projection;
   },
-  
+
   addStyle: function(style) {
     // may need to do better flattening, etc.
     if (Object.prototype.toString.call(style) === "[object Array]") {
@@ -179,30 +179,31 @@ Map.prototype = {
     }
     this._processStyles();
   },
-  
+
   setRenderer: function(renderer) {
     if (renderer.renderImage && renderer.renderGrid && renderer.processStyles) {
       this._renderer = renderer;
       this._processStyles();
     }
   },
-
+
+
   /**
    * Triggers all the map's datasources to prepare themselves. Usually this
    * connecting to a database, loading and processing a file, etc.
-   * Calling this method is completely optional, but allows you to speed up 
+   * Calling this method is completely optional, but allows you to speed up
    * rendering of the first tile.
    */
   prepare: function() {
     var projection = this.projection;
-    
+
     this.datasources.forEach(function(datasource) {
       datasource.load && datasource.load(function(error) {
         datasource.project && datasource.project(projection);
       });
     });
   },
-  
+
   _processStyles: function() {
     this.processedStyles = this._renderer.processStyles(this.styles, this.assetsPath);
   }