After writing about the stages of game development, it occurred to me that I used some terms in there that have very specific meanings for me, which might have value to others as well. I think of these things as "gamestuff", as in the primordial things from which games emerge. Having a taxonomy of the different things that go into games helps organize my thoughts and helps direct which things I should be working on at different stages.
Rules, when I'm talking about gamestuff, doesn't really mean the rule book or text on cards, although those are the places that rules are expressed. Instead, what I'm referring to is the methods of manipulating the game state of the game. The rules tell the players what things they are allowed to do and not do in the game. This may seem like an obvious thing, but the more interesting part is what rules are not. The specific numbers within a game are things that I don't necessarily consider part of the rules, nor are the specific cards, special powers, and other exceptions present in a game. Those fall into another category, and I treat them differently when working on a game.
The rules are the most important things to sort out early. Knowing that cards move like this, that dice work like that, that points are going to be won in these particular ways, these are the things that can make a design unique and interesting. If I can't figure out what the rules are going to look like early, I don't have a game.
Content is the collection of details of specific bits in a game. The content consists of the things that are manipulated by the rules, especially things that have unique properties. The manifest of cards in a design, the list of heroes, the details of spaces on the board, these are all pieces of content. They interact with the rules in many ways, and are obviously crucial to how the game works.
An important difference between the rules and content is that the content doesn't need to be complete to evaluate the rules. They will change in tandem at times, but I can create a subset of my content and still use that to validate the ideas in my rules. I'll usually create just the bare minimum of content initially to see if things are going in the right direction. I explicitly do not create anything close to what I think is the full content list until well into the design. I also assume that I'll need to create at least twice as much content as I think I need, because I'll end up throwing at least half of it away.
Components are the bits and pieces within a game that don't have unique data associated with them. Usually, these follow in lockstep from the rules and content, and you'll just need markers and counters to keep track of the game state that arises out their interactions. However, sometimes components can feed back into the other gamestuff you're working with, and it can pay to work out your component list mid-way through your design process.
Parameters are the numbers that go into a game that can be changed independently of the rules and content. How many points do players need to win? How many cards do they draw in a hand? How many workers do they start with? If there's a number I can change without having to re-write a bunch of stuff, that's a parameter. I love parameters in games. They satisfy my mathematical side, so I find them aesthetically pleasing, but they also give me lots of levers to fiddle with for balance purposes.
I'll fill my game in with some initial guess parameters early on, and then leave tuning those parameters until later in the process. Once I have a great feel for how all my systems work together, I will have a better idea of how to tune the parameters and, more importantly, how things will change in the system as those parameters are updated. Parameters are fantastic for making sure that different numbers of players work properly, for adjusting game length, and otherwise making the game hum perfectly.
This is the area where I tend to use simulation the most. Writing a program to run a bunch of "games" quickly can allow me to very rapidly measure the effects of changes in parameters. In some cases, the parameters are a matter of feel, and it requires testing at the tabletop. In others, I can often narrow down the range of viable parameters using computer assistance.
Games can have different quantities of these types of gamestuff. Foresight has rules, a fair number of parameters (points per trick, points per bid trick, winning threshold, number of face down cards, number of bids), and a little content (primarily, what things are on the backs of cards). I actually ended up shaking out the content fairly early and not touching it, while the rules and parameters got a ton of iteration. Meanwhile, Ascension at Firepeak has about the same rules weight as Foresight, although those rules were in a lot of ways easier to sort out. But there's tons of content (36 unique spells, 60 creatures) and really only a couple parameters (hand size, number of discards to research). Killing Monsters and Taking Their Stuff has a pretty minimal set of rules, an absolute ton of content, and so far has a few parameters (damage for different dice combinations, cost of levels). I'm hoping I'll be able to add more parameters as I go.
Thinking about the different types of data that go into a game and when I should be working on them has helped me concentrate on the right things at the right time when I'm designing. Worrying about content too early leads to churn and frustration, and trying to pin down parameters while the content and rules are in flux is a waste of time, as I'll just have to repeat that tuning work down the line. This taxonomy has been helpful for me, and I hope it can help others as well.