Q2 engine is an evolution of Q1 engine, as Q3 engine is a evolution of Q2 engine. As I said, I know this pretty well (I'm lead coder at warsow.net, which is based on Q2 engine and does everything Q3 does). We can argue on if the jump between Q1 and Q2 is bigger than the jump between Q2 and Q3, but this isn't my point. My point is that both those jumps aren't any big, they aren't really jumps, but a constant evolution. The step between Q3 and D3 is really a break appart.