Sunday, January 20

Layers and D20

This is an attempt to describe the different layers using the D20 System. The reason I chose this is that I can use the information in the SRD, which is open to use. Other possibile systems to analyse in this way would be Fate or D6.

Apart from the core rule, each game system has several individal parts, which all can be analysed in this way. For instance, the magic system in the D20 System can be considered a system in itself, and therefore should be analyzed as a separate part.

The System

As mentioned in the previous post, all actions are measured against how difficult the task is. The solving mechanism is random and linear. This means that extreme results are fairly common (the average roll is just as common as an extreme high or an extreme low).

This means, for instance, that adverse or positive circumstances will affect all participants in a contest the same. If the result-curve is bell-shaped, then a skill increase will have different statistical effects depending on the skill level of the character.

The system measures degree of success. Even though it's not always used, it's possible to calculate not even if someone succeeds or fails, but also how well they succeed (or fail).

Each task has a set level that says how difficult it is. In contests between two characters, this level is dynamic and decided by the opponent. Once again, since all results are linear, adverse or positive circumstances affect all participants equal.

The Engine

This is where we look at the implementations of the relations and behavior described above.

A classic way to get a linear random result is using a single die. We can chose to make a high roll good or a low roll good. This won't affect the statistical outcome, but there is a difference in usability and understanding of the system. Saying that a high roll is good is most often more intuitive.

A good skill gives a better roll. There are different ways to implement this:
  • Addition: Skill + roll = result
  • Multiplication: Skill * roll = result
  • Random addition: SkillRoll+roll = result
  • and many others
This choice could be said to be made at the system level, since they affect the basic behaviour of the game. There are two linear methods, addition or multiplication. The most easy and straighforward of this is a straight addition.

Since higher is said to be better, we say that if the result >= Difficulty, the task is a success.

The Game


This is where the rules meet the user. As of now there is basically one important choice to make, and that is what kind of die to use. The above rules are usable no matter what kind of dice we are using. No matter if we are using 1D6 or 1D100, the above rules and descriptions still apply.

The choice of die affects a couple of things though. Ease of use (lower numbers are easier and faster to add up) and granularity (a span of 1-100 gives more detail than 1-6) are the two more important. In this particular case, a D20 is used. This means that each skill-level gives a 5% chance of success. It's a span that gives a fair amount of fine tuning, as well as keeping the number relatively low.

Notes

This was a first attempt att analysing a system with these three levels. As said before, this modell is a work in progress, and it will be more fine tuned and defined as it is used more. This may also mean that the descriptions above could change.

3 comments:

Anonymous said...

So, basically every layer further narrows down the scope of the last one.

I am missing any theoretical reason for using exactly these three layers, but I suppose it is easier to work with a set framework.

Your model seems to be about mechanics (the interaction of resources), and issues like what they are used for are outside the scope of it.

Looks like a useful way to think about mechanics.

Ulf Andersson said...

When starting to think about these things, I used software development as one of my inspirations. The three levels could (very broadly) be analogous to algorithms, implementations and the GUI. In a way, you are right in that every layer narrows down the last one, in that it makes it more specific.

The three layers aren't exactly defined so far (apart from my idea above), and my hope is that with some more examples (and input from the outside) they can be more refined.

The model deals a lot with mechanics, and there is a basic assumption that "system affects gaming experience", which I do belive it does. If someone don't, then perhaps this and similar models are a bit superflous.

With that said, there are two parts of the mechanics. The statistical outcome and the mathematical behavior of the system and the experience of the user of said system.

While it can seem that it's a fairly "mechanical" analysis, what's important to me is the interaction between the mechanics and the user. One example is roll-under or roll-over systems. Statistically they can be exactly the same, but there is an almost intuitive connection between a high number and a good result.

I think that all levels of a system affects the experience of using that system, but perhaps in different ways. My aim is to discern where a certain problem lies in a system. Where does it appear? Is it based on the algorithms used (we shouldn't have used a linear system), in the implementation (roll high or roll low) or in the UI-system (no, three-digit numbers take to long to calculate in a fight).

Just one last thing to clarify the difference between the first and second level (that helps if you are mathematically inclined, if not it might just confuse you even more ;-) )

The relationship between speed, distans and time can be written in many different ways. Distance = speed*time, time = distance/speed and speed = distance/time.

All of these describe the same relationship (the faster you drive, the faster you get there). This would be on the first level.

The second level is where you choose one of these forms because it suits the situation the best. If I always have the time and the distance, and need to calculate the speed I would keep to the speed = distance/time formula. This would represent the second level of the game.

The third level is basically how you present this formula to the user.

.. this of course, being a VERY rough image of what I mean.

/McW

Anonymous said...

I do study and think math, which makes all those formulae seem the same to me, because they are the same thing, dammit.
Units of measurement would the analogy for the third layer, right?

That said, I do see your point and will follow the project with interest.