Having recently noticed the complete lack of games that have a nuclear winter as their setting, I thought that Cataclysm could provide a nice framework to actually make the first survival game in this setting. I have listed some of what I think should be main aspects of the mod/scenario to get some feedback and remember them so that i can start working when I have time.
-Temperature dynamically affects monsters. Under extreme cold, zombies and other creatures may freeze, resulting either in a frozen animal or a frozen dead body walking toward you. A frozen monster is slower, brittle and weak, the real danger comes not from fighting them, but from the temperature that caused them.
-Freezing rivers/lakes/ocean. Large bodies of water should freeze if the temperature gets low enough.
-Extreme weather affects the player. Things like blizzards and extreme storms should reduce perception and slow the player. This shouldn’t affect zombies at all, unless temperatures are low enough for them to get frozen, in which case you better start searching for shelter unless yo want to die from hypothermia.
-Fallout. Possibly in the form of irradiated snow, this would replace acid rain and will irradiate you and the ground if you get covered by it, the environment radiation caused by it should last some days
-More complex underground. As of now, the underground of cities is a rather bland place, sewer and subway system should be expanded and overhauled to provide with places to call home/explore as the above ground freezes over. There should be the possibility for NPCs to form Metro 2033 style settlements underground.
-More common underground wildlife.
-Destroyed and fortified versions of the existing buildings. Assuming that at least 3 months passed for the nuclear winter to set in completely, you should find more extensively looted and destroyed buildings as well as shelters with dead/hostile NPCs inside them. In general, food and water should be scarce in the aboveground forcing you to resort to hunting inside the sewers for sustenance. Builidngs like Public Works, Evac Shelters and Waste treatment Plants should have high chances of being modified into shelters.
-Ability to spawn underground. or in small shelters (Already coming).
-More widespread Radiation. After all a nuclear war had to happen for you to end in this situation
-Eternal Dark Winter.