Gas, fluid flow indications and mixing

[LeChatNoir]

Currently as far as I can see there is no way to determine directions of gas or fluid flow, without this you cannot find the problem areas or whether the measures you are taking are having any effect, positive or negative, or even areas that will be a problem in the future.

As for mixing it seems that the voxels can only have one material in it(at least according to the interface), which makes a different substance just float around nigh incoherently and visually roughly.

If the substances could mix, when they aren't incompatible, like water|oil, it would be smoothly enveloped by the other substance instead of just displace it.

Easy to add to display:
Flow indications, an arrow pointing opposite from previous point the substance was in.
Mixing, just have the primary toxicity\breathability overview with selection for specific gases/fluid.