Design Docs Release?

I am trying a new extension to the graph-hopper engine that could take care of Live Bus Arrival Information. But before I could Implement that, I am overwhelmed in understanding Graphhopper just through skimming code and limited readme.
Although there are good number of comments, it is really hard to understand the overall Design of Graphhopper in a decent amount of time(the whole flow and the design choices). It would be really useful for me and other open source contributors if there is any Design Documents available that you could share with the community.

and limited readme.

Why not look into the documentation?