Oh well.
I've probably written it somewhere, but I'll write it again. It is impossible to write a client game and the base class library (or is that called an "engine" nowadays) at the same time. I've seen this technique attempted several times now, all as a result of bad planning. They've always stretched the project's schedule unnecessarily.
Again, oh well.
As you can see, I need motivation. Somebody tell me something nice.