... now with 35% more arrogance!

Tuesday, May 17, 2011

Mechanics-Neutral Rules

Check out this table:

You've seen variations of it before: it's the Liber Zero table to "universalize" ability score rolls, reaction rolls, and rolls to open doors, avoid wandering monsters, and other situation rolls. All I've done is add a d10 and d20 column plus a column for modifiers.

What lead me to do this? A couple things:
  • A post a few weeks ago about using the standard saving throw categories (breath, petrification, poison) as suggestions only, improvising new categories for falling rocks and the like as needed;
  • A forum discussion which turned into a debate about roll under vs. roll over and d6 vs. d20.
My thinking: it would be easier to divorce saving throws from the old school fixed categories (or the new school Reflex, Fortitude, and Will) if you could just say "this class has a Low resistance to wands or rays that can be dodged, but a High resistance to other magic". Or: "the rocks falling from the ceiling are easy to dodge (Very High chance of avoiding.)"

Similarly, we can avoid debates about whether all rolls should be OGL d20, Target 20, GURPS-like 3d6 under stat rolls, or pretty much any other non-dice pool roll by just describing rules in terms of Hi/Lo and directing people to a universal table that gives you a value that will work for your system. The rolls won't be *exact* across systems, but it will actually be mechanics-neutral in terms of Roll High or Roll Low, or Roll 3d6 vs. Roll 1d20.

If you are using Roll Under and your target number is described as Lo/Hi, look up the label on the table, then read across to the column for your dice mechanic (Xd6, 1d10, or 1d20.) That gives your target number.

If your difficulty is described as Lo/Hi, look up the label, then read across to the Mods column; double this for 2d6 or 1d10, triple for 3d6 or 1d20*. No, the probabilities won't match, but who cares? You're using the same kind of roll for a given situation every time. Add the mod to your roll. If higher rolls are better, add the mod to your target number instead.

*Edit: I'm considering changing this to double for 3d6/1d20 and no multiplier for 2d6/1d10, to keep bonuses small. There will certainly be some situations where the mod will be smaller or larger than indicated; these are merely the suggested defaults for adapting your preferred mechanic to the Liber Zero rules. I have some other potential changes I'll put in a follow-up.

If an advantage or magical benefit is described as Lo/Hi, find the mod as above, but add it to your target number if low rolls are better, or add it to your roll if high rolls are better.


  1. Here's something I started once, but never got around to finishing...

    Linked on my page is a graphic and an excel spreadsheet with my attempt of bringing unity to the variety of players out there...

    All Systems - a somewhat universal guide

    Currently I've really left my roots and have been trying to wrap my mind around HeroQuest and WordPlay (I know, a huge jump, but I'm getting old and kind of like taking the path of least resistance)...



  2. It looks like you were trying something a little different: creating player unity. Whereas I'm just trying to shift the focus away from what dice you are rolling to the rules surrounding the mechanics: rolling for events rather than making skill rolls, tying monster challenge to dungeon level rather than character level, things like that.