Salem

Just out of curiosity why the developers didn't use Unity3d?

l0l

For a couple of reasons, but most importantly because of my general aversion against using libraries for things that impose models on me outside that intrinsically defined by the task at hand. I find that such libraries drain more time and effort than the gain I can extract from them because of the time required to even understand their intended model and usage, the immense effort required when wanting to do things outside of that model, doing general "impedance matching" with the model, getting into the code enough to fix bugs in it, &c&c&c.

I find it much easier, then, to just write my own code and get the exact model that I want.

See, I answered the question in earnest. ^^