update activity

Author: maptastik

activity_03-01.md

@@ -24,3 +24,9 @@ In this activity you'll be using CartoCSS and TileMill to make a choropleth map
 10. You should see the *Add Layer* window. Fill in the **ID** field with a short name for the layer. You can name it whatever you want, but it's helpful to name your layer something that describes what it is. (I opted for *tracts*). Select lucasCo&#95;hungarian&#95;tracts.geojson dataset wherever you have it saved. Leave everything else as it is and click **Save &amp; Style**<br /><img src="https://maptastik.github.com/os-webmap-workshop/images/tm-map4.PNG" width=100% />
 11. Alright! You've loaded in your data. You'll see some default cartoCSS for our tracts layers has been loaded into the style.mss pane on the right. Also note that in the bottom-left in the *Layers* window, we now have our tracts layer listed. You may initially not be able to the actual map of our tracts. In the *Layers* window, to the right of #tracts is a magnifying glass icon. Click that and the view will zoom to our tracts<br /><img src="https://maptastik.github.com/os-webmap-workshop/images/tm-map5.png" width=100% />
 12. Let's take a look at the data? What are we going to map? In the *Layers* window, to the right of #tracts is a table icon. Click it and you should see the attribute table of the tracts data. We've got too attribute fields that were joined from ACS Census data. **t_hung** is total population in the tract claiming Hungarian ancestry. **p_hung** is the percentage of the population in the tract that claims Hungarian ancestry. Because we're making a choropleth map, it's best to use normalized data. We'll be working with the **p_hung** field for this map<br /><img src="https://maptastik.github.com/os-webmap-workshop/images/tm-map6.png" width=100% />
+13. In the stylesheet pane, we have our default styling for our tracts layer:<br /><br />`#tracts {
+  line-color:#594;
+  line-width:0.5;
+  polygon-opacity:1;
+  polygon-fill:#ae8;
+}`<br /><br />These style description give the map it's current look, but there are many properties of the polygon's fill and outline that can be edited. You can access the built-in CartoCSS reference by click the curly-brace button on that vertical stack of buttons mentioned earlier. Additionally, Mapbox includes the [reference](https://github.com/mapbox/carto/blob/master/docs/latest.md) on their GitHub page along with [several examples](https://www.mapbox.com/tilemill/docs/crashcourse/styling/) in the TileMill documentation on their website.<img src="https://maptastik.github.com/os-webmap-workshop/images/tm-ref1.png" width=100% />