Game loop

Let's start with the basics.

I need to spend a while thinking how I want to tackle some of the basic
design issues with this kind of game:

*Level of detail: We have a big planet, and we need to be able to
seamlessly render parts of it at any level of detail.

*Position accuracy: If we use floats to store position, our fighter will
always be very far away from the center of the planet. There will be
glitches and artifacts. Working with nothing but doubles also doesn't
make much sense. I'll figure something out.