The achievement guide says that you get achievements, 20G for every mission you complete. But I can't figure out when the missions end. I have went through several pauses where the screen goes widescreen and in the lower right it says a name of something. I just got Halo 3 for Christmas and started playing it a couple days ago. But why haven't I been getting my achievements?
How do I change the difficulty?
How do I change the difficulty?