The game would be here if here if you want to play it, will only work on windows and is the non tiles version:
The game doesn’t become darker/colder over time, it’s probably not considerably harder to make it that way; but because I wanted to play the final stage it drops you already into the perpetual night. You might want to do stuff like increase the lifetime of light sources and play with the zombie nightvision mod on.
It runs noticeably slower than vanilla, because I don’t actually know how to compile the optimized version.