Has talked about making and maintaining IPs, wants to go through an actual example. Cain will go through an idea from his design notebook, expand on it, and show how it can become an actual design. Will do it in the recommended setting ----> story --->system order.
Wanted to do a post apocalyptic game, but without nuclear war or any of the other things he had done before. Had a new idea, what was going to be different was that a lot of people were gone, there were a lot of monsters, wanted more monster variety than Fallout's collection of ghouls and radioactive monsters. Wanted more variety, but wanted a good reason for that variety. Wrote a hook on one page of his design book. Wrote it down in about 2015. Not going to develop it. Cain notes a lot of YT channels has started saying "Let's Get Into it!".
First, you can't just go to someone with your idea IP and say let's get started, you need some actual material and development on it.
Setting was post apocalyptic, won't say what happened for reasons he will elaborate on, but the cause explains everything else that follows. All the buildings are intact, most people are dead and you will find the bodies. Lot's of monsters running around, some hunting in packs, some fighting solo, some fighting each other. The protagonist would have been a five year old child. That is going to be a major hook for this theoretical game. When Cain wants to describe a game's high level story, he likes to explain the opening. It's generally a cinematic the player can't playthrough, it always ends one way. Fallout, you're a vault dweller, get kicked out, game starts afterwards. Arcanum, going to a new continent for a new job, blimp crashes, games starts in the wreck. Cain doesn't really like games that make you play through an opening you can't change. Feels like it is a waste of time, so would have that section dealt with in a cinematic. Five year old protagonist would have woken up in the morning, run downstairs, get cereal, turn on the Saturday morning cartoons. Whole weekend ahead of you of no school.
You hear a thump downstairs, then another thump, and would start to wonder why it's day but you don't see anyone awake. You go upstairs, push open your parent's bedroom door, your parents are brutally dead and your sister looking crazy is standing over them. She turns and looks at you, screams and jumps at you. At that point, your golden retriever tackles her and rips her throat out. What looks like a rescue turns into something else when the golden retriever looks at you and he has red eyes and looks clearly different. Slobbering and growling at the protagonist, you realize he just went after the biggest threat and the protagonist is next. You turn and flee, closing the front door to block him, the protagonist runs out the fence to their block, hearing distant screaming around them. The protagonist walks to the only safe place they know, school, slipping through a gap in the fence they know about from recess. Everything in the school has been locked down, as the screaming and shouting intensifies, the protagonist notices a small opening in a bathroom window. Squeezing through that after getting some height with a trash can, the game begins in the bathroom.
Cain breaks it down into three acts. Act One is Survive, how do you not get killed? How do you get food? Act Two is Explore, once you've eaten everything there is in the school, you start to explore the school, the school ground, make forays into neighboring houses, maybe even return to your own. Meet some other survivors. Act Three, maybe the protagonist is a bit older. How do you find out what caused everything, how do you recover and move on? How to get past pure survival.
Now onto system mechanics, you are five, this is not a class based game. No five year old barbarians, no five year old telepaths or wizards. Skills in the game, but you don't have any. All skills start at 0. You can't cook, you can't read, you can't drive a car. You will probably stay that way because who is going to teach you how to read? Cain's goal for the skills would be things that a child could learn on their own. How to scavenge, how to hide, maybe how to cook. But probably not how to learn to drive or read. There could be notes and books, but to you they are just symbols (This would be quite helpful for art as now they don't need to worry about localizing text.) You could see a sign with an arrow or an X and some word you don't know and have to determine from context. Even recordings could be done as partial gibberish, if the child protagonist turns on a radio and some lady is announcing a warning, they could easily not understand a lot of it and it would be blahblahblah. "Please stay in your homes, do not under any circumstances blah blah blah."
What would be the elevator pitch? Cain jokes about FROM THE CREATORS OF FALLOUT because he knows that annoys some viewers. He would probably pitch "Can you survive an apocalypse as a child?" Probably better elevator pitches, but that at least engages people. What presentation would you give publishers? Cain had those acts detailed but particularly the first act was detailed was because that is kind of want to do with publishers to hook them. If Cain had time and available artists, he would get a cinematic of the opening prepared. Otherwise, he would at least get a concept artist to get that done as a set of slide to show while Cain narrates it. Publishers have imagination, but they need a little poke. Cain would then talk about the hooks of the game, it has a few interesting ones. You start as a child, you start as an illiterate child, you start with 0 skills. Interesting, things you don't see in a lot of other games, but not so bizarre you can't comprehend them, you are already starting to wonder about them. Evocative hooks, something Cain encourages people to do. If your hook is 'You are a boingalock from Planet Zebon', that means nothing. A hook like "You are an illiterate child who knows nothing about the world and the world has ended" let's the player compare it to the standard apocalyptic game of going out into the desert to shoot mutants. You may talk about this with publishers, you may not, but you should be able to self-evaluate the pros and cons of your IP.
Self evaluating the this IP, it has the pro of having a lot of mysteries. What is going on, why are so many people dead, what are these monsters, what caused all of this, how am I going to survive? Some are time critical, others can wait, but you find out about them all. It could also be a trilogy, shift the 3 acts into 3 games, some publishers love that idea, others don't. Literacy as a hook is interesting because you rarely have an illiterate protagonist and you can save on writing lots of books and notes and also don't have to worry about translating them into 20 different languages. Cain sees two big cons; people getting fatigue from Tim Cain's post apocalyptic games. Already done it a lot, even in Arcanum when you realize there once was another industrial revolution and it was wiped out. Cain sees Outer Worlds as Pre-Apocalypse. Cain would say he hasn't done pure post apocalypse in 3 decades, so he should have another chance. Going back to his idea that you should only use amnesia once, he would give someone a pass if they want to use it again 30 years later. Another big con, which people have personally told Cain, is that people aren't going to buy this if you play as a child. You show the child getting killed, which is a negative. Cain uses LIMBO as a counter example, as most of that game is playing as a child and getting gruesomely killed every few minutes, more often than in Cain's theoretical game. It has a mode where you can make the screen black out before you die, and if anything that just makes it more awful as you can hear the character die and a bunch of squishes and squirts. Also several games released since with child morality, Cain references the Dead Island trailer with the zombie kid getting thrown out. Clever people turn this con into a pro.
Wrapping up, notice Cain didn't go into extreme detail in places. Cain didn't really talk about the skills, or the cause of the apocalypse. Some of those he knows, like the cause of the apocalypse (And is withholding it because it's a nice mystery), others he doesn't really know like what skills he would use exactly. For both of those, he has the goals. The cause of the apocalypse constrains how people die and what kind of monsters there are. His general idea of the skills constrains what the player can learn or wouldn't know, i.e wouldn't ever learn driving, might learn cooking. These are all a good starting framework, a framework is very important at this stage. Some designers require frameworks, and will freak out without one. Other designers hate framework, and would push up against Cain/Your own framework and try to get it to move. A lot of designers will notice the framework, notice gaps in it, and come up with very good ideas for it. Once others start to fill in your framework, they feel ownership for those ideas, and they will do excellent work because it is their ideas. Cain likes frameworks, not having all of the details. Design doc terms, cover most of the basics, and have goals for those things. If someone isn't meeting those goals, i.e designing the wrong set of skills, you can use that framework to discuss it with them. Cain would rather not have continuous arguments about the game's goals into a year or two, so talk about it early.
Hopes this walkthrough helps you develop your own ideas for an IP.
He also nails the personality of some posters here... Tim, if your reading this... 
!