April 05, 2011

Die rolling in Gaia Gamma

One of my basic decisions for Gaia Gamma is to only use six sided dice. I want Gaia Gamma to be a really old school game... so old school that polyhedrons other than d6 are not even an idea. But the idea of using d6 comes with a corollary that I strongly try to adhere to in my game designs (call it Shadowrun trauma):

Thou shalt not throw excessive amounts of dice.

As far as I am concerned two dice is about right for the standard maximum to roll. Three already is a bit too much. Although I always enjoyed GURPS less would have been more.

And then there is my next corollary:

Thou shalt leave room for development.

Which basically means that I do not like very narrow attribute ranges. I want to able to develop characters and one of the best ideas to be taken from D&D 3rd edition IMHO is to be able to raise attributes as characters get more experienced. This makes the game less static and gives even weak characters something to strive for. But this doesn't work too well with narrow attribute ranges because advancement again becomes a pretty static things and I also like the idea that every new level (in a level based game) should offer excitement and new experiences.

What does this mean for Gaia Gamma? I decided to draw inspiration from a very old game design of one of Gary Gygax's former companies. In 1987 New Infinities Productions, Inc. released the venerable Cyborg Commando (also a post apocalyptic game with a very different kind of apocalypse) that - as far as I know - was the first game to multiply two dice in order to find a die score. Cyborg Commando used 2d10 (probably due to the pretty neat distribution spread), for Gaia Gamma I am going to use 2d6. For all major tests, that it.

The notation will be 2dx which means that you roll two six sided dice and multiply the results to get the final score. E.g. rolling a 2 and a 5 yields a final of 10.

The final spread ranges from 1 to 36 (although quite a few numbers can't be rolled at all). The latter is ok for me as this leads to the situation that not every attribute increase (or skill level increase for the matter) will lead to an actual improvement. Even better - the higher a score gets, the fewer numbers can be rolled. While I do not want to discuss the merits of the actual spread (is it realistic or not? who cares in a world of mutants?) I like it's general makeup: Wildly varying results can be occasionally achieved but the main distribution still centers around 10, which is nice for the classical attribute range of 3-18 (and ensuing attribute tests). As a consequence skills also will be centered around an initial 3d6 throw (at least for primary skills - more on that in a blog post to come regarding areas of expertise).

The chart below shows the actual distribution of rolling a specific score or less with 2dx:

One interesting problem arises from the actual number spread on the chart below: It becomes very hard to define meaningful difficulty modifiers if you go for a "roll under or equal to" system - which I intend to do as I believe that doing something more difficult after already being required puts too much strain onto the player.

But I have what I believe to be a good idea about that - more on that in tomorrows post!


  1. I really enjoy the variety of numbers available while using only 2 dice. The only problem I can see is that (assuming the DC for this is 10) you will encounter small failures or huge successes. The fail is from 1-10, and the succeed is from 10-36. If you have any varying results from success/failures (i.e. criticals,counterattacks, amazing amounts of bonus treasure)... I like the concept, but it needs some kind of scaling/ratio to balance it out...
    Really good idea though, though I love the sound of rolling dice, and as many as possible if I can. As far as d6 goes, I really enjoy the West End Games Star Wars RPG, and its actually very easy to use (even though you roll between 2 and 8 dice for most things). I just began following, and I have yet to read any thing posted after this, so forgive me if you have discussed this system in a later post.

  2. Actually you raise a very valid point that needs to be considered in more detail. I have noted it down to be blogged about in the future.

    I blogged in http://www.gaiagamma.com/2011/04/handling-difficulty-modifiers-in-2dx.html about a very simple approach to die rolling which suggested to not even have difficulty modifiers. In that scenario levels of success would be totally moot :-) But as (for now) I decided to go with the method suggested in http://www.gaiagamma.com/2011/04/handling-difficulty-modifiers-in-2dx_07.html (which introduces some coarse difficulty levels) level of success might be a topic.

    My gut reaction was to state "The Mutant Master is responsible for interpreting the level of success of a test - defined by the margin between rolled score and required score - according to his ad hoc evaluation of the situation at hand", meaning "just wing it" - which seems to be very appropriate for an old school game ;-)

    But more on that in future posts... good point!