ExposureThe exposure time should be afew minutes, long enough to get started on a fort and for immigrants to get inside. Justify this with the fact they are all wearing emergany oxygen tanks or something.
The only people that can be outside for long periods of time are people that can equip armour, such as military and hunters. It's kind of conveniant due to lack of trees. Cave adaption isn't really a problem if your colonists are inside all of the time anyway. It will be funny to see them take trade items up to the depot and then puke everywhere though.
There should still be war, from other pissed off factions.
WeaponsHammers = Wrenches
Swords = Plasma cutters
Axes = Drills
Crossbows = Guns
Shields = Large Riot Shields
Bucklers = Small Riot Shields
Ballistas = Siege lasers (produced with cut gems)
Catapults = Artillery Cannons
Obviously a space suit that has been shot up isn't much good, so make them different sizes. Or use different plugs or something to avoid the player massing loads of sets of space suits.
CropsSpace Helmets = Plump helmets
Hogtail = Pig tail
Spaceweed = Cave wheat
Spacepods = Sweetpods
Redweed = Dimple cup (but red dye)
Martian Fungi (Processed into wood, for charcoal and building)
Add advanced and high yeild crops, Algae that grows in 1/7 water.
Yellow Algae = Rocket Fuel (Booze)
Red Algae = Algae wafers (After being dried(milled) and cooked)
Green Algae = High Strength Cloth (silk) Not high yeild, but an interesting method of obtaining silk.
Trade2 types of trade.
Rovers. Like a normal trade depot for trading with colonies around the place.
Spaceships. Come enter from the edge of the map several z levels up and come down. The spaceships need atleast 3 z levels above them and 3 wide. Haulers shouldn't die, since they have these "emergancy oxygen tanks". Used for trading items back to Earth. One one of these should come a year, or even less, and it should be an event. Crafts sell for lots of money, and other things exotic to earth. They sell stuff like seeds and animals more often. If the trade depot is inaccessable they will pass you by, so you need to put some effort into digging a hanger. In order to make spaceships require just a little development, only allow trade depots to be placed underground.
Food, alchohol, wood, metals, gems, cloth, clothes, dye, armour, weapons are all trade commodities. Pretty much the same except for the fact bone crafts are a little rarer, unless you decided to bring breeding animals along.
CreaturesEarth livestock, cats, dogs
Martian cave creatures
Monster cave and surface creatures