Congratulations! You are at the end of a long journey of mastering OpenLayers 3. In this last chapter, we extended our knowledge even further and learned how to customize, shrink, and extend the source code of the library as well as compile our own version. We also learned how to compile our own application with the library and create a standalone documentation for our customized product.
There is only one thing left for you to do. As every book has a physical limit, we could not cover every little part of the library. As now you have a solid basis in application development with OpenLayers 3, go on, and create your own great applications. Practice, find the best solution for your case, and always keep up with the changes, and the new, cutting edge features. Good luck!