Have been building a game called Rise: The Vieneo Province.
Vieneo is a terrestrial moon (all details can be found here) but we have a Nitrogen (ipp: 2006), Helium (ipp: 578) Oxygen (ipp: 11) and Argon (ipp: 6) composition.
Questions have been raised about the viability of having field crops on the surface since there is no CO2 and lack of animals causing a gap in the carbon cycle, etc. We don't really want to be able to walk around without some kind of biohazard suit and rebreather (level of effort to animate, etc).
The sky is overcast (again so we don't have to render the whole planet from orbit). There is liquid water on the surface (13% coverage). Atmospheric pressure is 2631 mb so if we had to add a little CO2 it would go a long way (assuming plants work with partial pressure like humans do). And maybe the rebreather could catalyze the CO2 to get O2 or something to that effect so we don't have to add O2 to the atmosphere.
Propulsion of the vehicles in the game depends on the mass of air for ejection but the energy does not require combustion.
- How can there be field crops - i.e. what is the minimum change to support them?
- Is it survivable from a human standpoint with minimal protection (no space suit here... just something to keep air inside separated) and believable that a suit is required at all times.
- Is it sustainable? Does it make sense that it is overcast with so little water on the ground? I have temperature ranges too which can be easily adjusted.