So, you've hit that point in the game where everything seems to be doing well. Your economy is stable, your research is on schedule, you have enough defenses to hold of all but the most determined enemy. There's only one problem: you're 100 points behind. This is the situation I seem to continually find myself in, now that I've moved up to Prince difficulty. There's no room left to expand, and even though I have a technological superiority, I can't seem to catch up with the other civs. So, what I'd like to know is: how do you catch up in the mid-game?