Ok guys, stick to the topic
You got the right idea, Tidus, as far as the land surface. I'm envisioning a dark bluish-gray hilly surface polished like marble, except for a few areas that still have carbon debris and rubble. The water will shimmer black-violet-indigo, and yes the whole atmosphere will be dark. The contrast with the distant sunlight will be sharp, however, and buildings and vehicles will stand out starkly.
Right now, the immediate changes will encompass graphic changes (almost entirely), all new cargoes and industries, and new vehicles (altho magnetic rail can be directly transferred. However, because of the change in "road vehicles" (equivalent to maglev "mine cars"), and hovering (as opposed to flying -- altho essentially that's what they'll be doing) craft, the Action pseudo-sprites will have to be recoded (which i haven't learned to do yet). We don't hafta change palettes or coloring systems; just stick to the template for the Temperate gameplay.
This will replace Toyland's scenario, for now, until we get the thing going and it's starting to take shape. Then we'll make it its own mod (a 4-set game, like the current TTD)
To answer your question, Bjarni, about why the moons of Pluto...I wanted a futuristic place where the advance of technology allows us to develop on other planets. Mars is overfictionalized, and the Gas giants are not really "colonizable." So i did some research on the moons of the outer planets, and chose Pluto and its 3 moons, mostly because little is known about these bodies, and as a creative artist, the less is known for fact, the more you can let your imagination run wild. But one minable moon is as good as another, as long as humans could build on it.
And don't worry about gravity on small planetoids; in the year 2565 (for the purposes of our mod), we discover how to apply the Grand Unified Theory, and by passing a resonated electromagnetic current through certain non-conductive materials, the gravitational mass of a small amount of matter (relative to a planet) can be amplified, simulating gravity. Of course, it takes A LOT of energy, which is one advantage of a nuclear plant.
One other thing if i don't respond right away; i'm not on the Internet at home, so to get to these forums, i go to the local library twice a week...