[Mohs Scale Of Sci-Fi Hardness:
1. Science In Genre Only: The work is unambiguously set in the literary genre of Science Fiction, but scientific it is not. Things run on Nonsensoleum and Unobtanium, and both Bellisario's Maxim (don't examine this too closely) and the MST3K Mantra (It's just a show; I should really just relax) apply.
2. World Of Nonsensoleum: The universe is full of Nonsensoleum with more to be found behind every star, but the Nonsensoleum is dealt with in a fairly consistent fashion despite its lack of correspondence with reality and, in-world, is considered to lie within the realm of scientific inquiry.
3. Physics Plus: Stories in this class once again have multiple forms of Nonsensoleum, but in contrast to the prior class, the author aims to justify these creations with real and invented natural laws — and these creations and others from the same laws will turn up again and again in new contexts.
4. One Big Lie: Authors of works in this class invent one (or, at most, a very few) counterfactual physical laws and writes a story that explores the implications of these principles.
5. Speculative Science: Stories in which there is no "big lie" — the science of the tale is (or was) genuine speculative science or engineering, and the goal of the author to make as few errors with respect to known fact as possible.
6. Real Life (aka Fiction in Genre Only): A Shared Universe which spawned its own genre, known as "Non Fiction". Despite the various problems of reality being "unrealistic", it is almost universally agreed that there is no other universe known so thoroughly worked out from established scientific principles.
I am aiming to be somewhere between 3 and 4 with this game.
EDIT: Your biggest issue is air pressure and cold-ass temperatures.]