I've been using the dark terrain as an additional handicap (it's slightly confusing to try visualizing w/o the terrain details and tougher to decide on some improvements). I have found the area of black terrain decreases as the game progresses (a small bit of terrain becomes visible and increases in size). The area where the visibility starts (and the time at which it starts happening) is different for each game. It is never at the center, always starts at the edges. It is also bigger the "farther out" I zoom (obviously as the focus of zoom in is toward black terrain).
I've attached 2 images that shows the area and what happens when I shift the viewing area (I reduced the color depth to 256 to reduce the sizes). Unfortunately, I don't have images from previous games to give a comparison, but I think the one's I have with the description gives a general idea.
I've attached 2 images that shows the area and what happens when I shift the viewing area (I reduced the color depth to 256 to reduce the sizes). Unfortunately, I don't have images from previous games to give a comparison, but I think the one's I have with the description gives a general idea.