I kinda like the defense idea. It forces you to think more about the environment you're in and the plasmids you would use for traps. I didn't really use traps too much in the first one. Also, it makes a lot of sense, considering you see a lot of big daddies defending a lil sister in the first game, now you jump to the other side of the fence. Its not a prequel either, its a sequel, and takes place several years after the events of the first game.