The Sum of its Parts - what is it, and how it's going

 I was supposed be focusing on Neon Knights and just do one RPG at a time, but then I got hit with this idea and couldn't put it down.

The Sum of its Parts is a horror game in which each player controls a different Fragment of a single individual (referred to in the game rules as the Self).  While it's not the first RPG to tackle this concept, one significant difference between this one and the others I'm aware of is that all Fragments are active simultaneously, instead of taking turns controlling the shared character.  Whoever speaks first gets to decide what the Self does at that moment, and if multiple players call out at the same time (or close enough) then they risk freezing with indecision at a critical moment.

Each Fragment has a different goal, and also different abilities and different knowledge.  If I can make it work for them to have different perceptions at times then that would be pretty cool (this would be really easy in play-by-post, but I'm not sure how it would work at the table).  For the most part, Fragments cannot communicate directly with each other - if one needs information that another happens to have, then things get tricky.

I have no idea what the rule system will look like.  I briefly considered adapting the dice pools from Don't Rest Your Head, but I think I'd rather do my own custom system.  It's totally up in the air at this point.

One thing I do know so far is that there are two stats which are shared between the whole group.  Cohesion is the health/damage track, which covers both physical and mental damage.  If it hits 0, that's a game over for the whole group.  Integration measures how well the Fragments are able to work together.  At the high end it would allow Fragments to communicate with each other, despite what I said earlier.  At the low end I'm not sure; maybe it would mean Cohesion damage, or maybe I can think of something more interesting.

The game is definitely competitive - each Fragment has their own goal, which is stated as "When ___, the game ends and you win."  But since they all share the same body, there's a limit to how much they can actually work against each other.  I'm excited to see how that part works out in play.

And then there's the setting.  My focus for the game might be about how the Fragments interact and interfere with each other, but they need something do to in order to showcase that.  My most specific idea, which got this ball rolling in the first place, is that the game starts with the Self waking up in a hospital bed or something similar, and a doctor (or similar) asking "Do you know your name," "Do you know where you are," and maybe a couple other cognitive screening kinds of questions.  So building from that, I feel like a constant should be that the game takes place in some kind of facility that does medical treatment and/or research - "legitimate" medical research lab, mad science lab, military hospital, etc.  There's an implication that the reason the Fragments became separated is something to do with the work being done there.  Broadly speaking, the activity of the game involves finding your way through the facility, maybe figuring out what's going on there, and hopefully getting out in one piece.  Of course the individual Fragments' goals might change that, but I think I need a starting point before I know what everyone is deviating from, and this is it.  Ideally what I'd like to do is start with a broad framework and then let random tables fill in the rest, so there can be more variety between play-throughs even if they all start with this same premise.

One other thing I've come up with so far, just as a side detail that seems like fun, is that mirrors have power.  My current idea is that the first time during the game that the Self looks in a mirror, it triggers the GM to ask each player a random question from a defined set (e.g. "What about your reflection looks wrong?" or "What you see triggers an important memory, what is it?").  Looking in mirrors again later on might have different effects but I don't know yet what that would be.

And that's where I am so far with this one.  I have a sense of what I want the narrative to look like, but I need rules, and I need random tables to build the Fragments and the facility (and maybe anything else too?).