Hello, I am an aspiring game designer, and this is my idea of an apocalyptic survival game.
First, theme music to set the tone of the game. http://youtu.be/i6OtF7daIPM
I've been thinking of making a game around the concept of every Friday the 13th, monsters would come into the world and wreck everything and kill everyone they come across. In between invasions, you do your usual scavenging and survival against the elements and hostile animals or bandits
I've come across the issue that there is a lot of time in between invasions, so I'm thinking of a time unit sorta mechanic to try to not bog down time between invasions. I've also thought about having mini-invasions on Friday and the 13th day of the month, which causes you to come in contact with the monsters a bit more often. However, I'm split between making the monsters more common, or having the encounters VERY tense and challenging.
Gameplay wise, it would run like an X-Com game, with a Sims element, probably. I think the Sims 3 trait system and general gameplay would work pretty well for an apocalyptic survival game.