It's a great game! I love it, but I can't stop thinking about the mechanics of the gasses in the real world.
To begin with, I don't know why there's no Nitrogen, as all breathable air is about 78% of it; we can't breath pure oxygen, that's why the molar mass of air is 28 g/mol, because it is a mix of nitrogen and oxygen mainly.
Now assuming we can breath pure oxygen, because maybe the lungs of those little duplicates are super developed, in the game says oxygen is 16 molar mass, but it should be 32 as it is O2, a single molecule of O would kill all organic matter. Chlorine for example is correct with 34 molar mass because it is Cl2, and not 17.
Another thing, which may be cool but not so necessary for the game mechanics, is to see the gasses getting trapped by water, in other words solubility of gases in water. CO2 and O2 are very soluble in Water, and even more chlorine! the solubility changes with temperature and pressure, the higher the pressure and lower the temperature the more mass of gasses it can contain, that's how sodas work.
For example if a tile is about 1000 L or ~ 1000 KG of water, then at room temperature 25C and normal pressure, it could hold a little more than a KG of CO2, That's probably a bit more than one tile of CO2.
Every gas definition and liquid