[cr0sh]

I was pleasantly surprised by the amount of useful comments in the code.

I remember when the source code for Descent was released; not only was the code somewhat opaque (unless you were experienced with portal-style engines), but there were hardly any kind of comments to help guide you along.

[SwellJoe]

Reading some of the docs in the source tree makes it apparent it's been ported to a bunch of platforms and for a bunch of different markets, and it looks like a lot of people have touched the code over the years. With an experienced hand guiding the process, that usually leads to good quality, in terms of re-usability, stability, and code comments. Being 19 years old is also good for quality...even if it's huge and scary and difficult to wrap ones head around in a short time, somebody has run into every possible edge case and weird compatibility issue in all that time, and they've probably fixed it. Old code bases aren't really fun to work on, but they are usually really productive to work on.