Timstone writes:
>> It really doesn't make any sense to me that my race evolves on a planet with a horrible climte, but only like planets with a pleasant climate.
Maybe it's not that far-fetched. When you look at the earth as a whole, for example, the global "climate" is pretty awful. Vast stretches of our planet are so cold they're covered with ice or snow for all or part of the year. Much of the rest is dry and blistering hot, or wet and muggy. Our ancestors evolved in just one of the earth's many climates and only spread to the other zones through the use of technology (fire, clothing, structures). If you want to visualize an "optimal" climate, think of an entire planet where you can go naked outdoors all year long, grow three crops a year, and your buildings don't need walls.
However, I agree with other posters on this thread that habitability of a world should be relative to the colonizing race. A possible approach is to drop SE IV's relativistic climate descriptions in favor of absolute parameters. How about average temperature, for example? Surface gravity? Sea level atmospheric density?
Race descriptions would then be amended to include the species' optimum (average) climate. Examples: rock/oxygen, 25 degrees Celsius, one G, and one atmosphere (humanoid); rock/oxygen, 20 degrees, 0.8 G, and 1.3 atmospheres (a cold-adapted alien species). To humans an earth-like world would be "pleasant", encouraging population growth; to the aliens it might be "mild" or "neutral", with zero or negative effect on reproduction.
On non-breathable worlds, of course, temperature and atmosphere would have little effect, but gravity would still influence habitability. In general a domed world would always have lower population growth than a breathable world with the same gravity, however unpleasant the climate.
Of course this opens a whole new can of worms with other game parameters (can you have a low-gravity race with high physical strength?), but I prefer to view the resulting complexity as a new opportunity for modders.