Comment 3 for bug 1516785

I think this would be a good design for the AI hints.

As to a progression according to map size, I was thinking something like

    building_limit = easy_limit * 2 * 64 / (map.width + map.height)

with 64 being the smallest map dimension. Or maybe

    building_limit = easy_limit * sqrt(64^2 / (map.width * map.height))