Explain reason for building in README

README.md

@@ -1,9 +1,47 @@
 # Mapolo
 
-A visual style editor for MapboxGL.
+<img align="right" alt="Mapolo" src="mapolo.png" />
+
+A free and open visual editor for the [Mapbox GL styles](https://www.mapbox.com/mapbox-gl-style-spec/)
+targeted at developers and map designers. With Mapolo everyone can design their own custom map!
+
+## Features
+
+- Completely free and open source
+- Visual interface for designing maps
+- Immediate feedback
+- Edit layers
+- No vendor lock-in, no proprietary base styles
+- Easy to deploy as single HTML file
+
+**Roadmap**
+
+- [ ] Add new layers
+- [ ] Support all layer types
+- [ ] Choose sources
+- [ ] Filter data from sources
+- [ ] Support zoom level specific values
+- [ ] Faster map feedback with custom diff algorithm
+- [ ] Tests for React components
+- [ ] Make it prettier
+
+## Reason
+
+Mapbox GL is one of the biggest innovations the GIS world and is the first cross platform framework to display maps on mobile devices, the browser and the desktop. Maps are styled using a JSON style document with properties described in the [Mapbox GL style specification](https://www.mapbox.com/mapbox-gl-style-spec/). The style specification is adopted in more and more clients such as Open Layers 3 and therefore the **missing piece in the puzzle is a style editor that is easy to use, free and open source!**
+
+In constrast to earlier approaches using [CartoCSS](https://www.mapbox.com/help/getting-started-cartocss/) the format is difficult to edit by hand but much more suitable for generating from an editor.
+As of today Mapbox GL styles are usually designed within the cloud based [Mapbox Studio](https://www.mapbox.com/mapbox-studio/)
+which is a great example how a style editor should look like.
+
+The big problem is that Mapbox Studio is not open source and you have to upload your data sources to external servers and
+essentially are locked in the Mapbox ecosystem. By reusing existing proprietary base styles you legally tie your style for use with Mapbox services. It is difficult to use other data source like [OSM2VectorTiles](osm2vectortiles.org), [Mapzen](https://mapzen.com/projects/vector-tiles/) or [Kartotherian](https://github.com/kartotherian/kartotherian) or even your own custom vector tile sources.
+
+This is why I think we should rally behind and build our own style editor for the Mapbox GL style specification!
 
 ## Develop
 
+Mapolo is written in ES6 and is using [React](https://github.com/facebook/react), [Immutable.js](https://facebook.github.io/immutable-js/) and [Mapbox GL JS](https://www.mapbox.com/mapbox-gl-js/api/).
+
 Install the deps, start the dev server and open the web browser on `http://localhost:8888/`.
 
 ```bash