A few questions regarding styles

First, is there any way to convert phpBB 2.x.x or 3.x.x style (not database) into punBB 1.3.4 style (I know this is unlikely to exist, but I am asking anyway)? If not, is there any way to, at least, partially perform this conversion?

Secondly, I've noticed that CSS file which comes with one phpBB style is 657 lines long. On the other hand, Oxygen.css alone is nearly 2000 lines long. Why is that? Also, Oxygen.css is quite cryptic to understand when compared to that phpBB style (at least to me) and I cannot find any documentation.