As ever these days, I started with the three questions to give myself a little better orientation as to how to tackly this project.
1) What's this game about?
This one was handed to me in the specs, in a fashion. It's about survival, and specifically not about questing. This means that character viability must be a big deal in this game. Generalized hit points, where you go from 100% efficacy to dead is no good here. A survival game needs to have a health system that has all different shades of suffering built into it, so you can, um, enjoy(?) the degree to which your character has progressed towards death.
2) How it is about that?
Many games focus on how it is you accomplish something. I'm thinking that if this game is about survival, it's instead got to focus on how you take various kinds of damage. In fact, right now I'm thinking that your only attributes all deal with how you weather different kinds of hardship and damage. The focus of the character is how he survives, not how he accomplishes actions.
3) What actions does it reward?
That's a good question. Since this game is about living to see the next day and nothing more, you could say survival is its own reward, but that's pretty tepid. So I think what I'm going to do is tap into some of the other specs and, in the spirit of old school mentality, say that teamwork will be rewarded somehow. You'll need to work together to survive. Old D&D was like this, in the beginning anyway, and I think it was always intended to stay that way, even if it really didn't the higher the levels climbed. So Another Day will have something in it that rewards working together.