Recently, both D&D and Apocalypse World have been on my mind, for various reasons. (Warning: It's late at night, so please bear with me - I'm not at my most lucid. However, the math here is really entertaining, so if you're into that kind of thing, do read on.)
* I find the basic ability score check in D&D (roll a d20 below the ability score) to be a great basic mechanic, and very D&D-esque in flavour, but inelegant when modifiers come into play. Modifiers are linear, and sometimes hard to judge ("should this be a roll at -6 or -7?"). So, I thought: how about we treat a "difficult" roll as rolling two dice, then discarding the better result. Like rolling at a disadvantage in D&D Next - this is roughly equivalent to a -4 or -5 penalty, a reasonable step down (-25% chance on average), a good chunk of difference in difficulty, very tangible but not overwhelming. It feels about right, which is probably why they chose this mechanic for "advantage" and "disadvantage" in D&D Next. Now note that rolling twice and keeping the worst result is equivalent to rolling twice and requiring both rolls to succeed... hold that thought.
* The Apocalypse World mechanic is fabulous and elegant, but has very discrete steps, which could be an issue in certain designs. It gives us three tiers of outcomes, and a nice bell curve.
* Using D&D stats in a game like Dungeon World is an interesting cross between these two games. We have things like "Strength 12, Charisma 9", but AW mechanics for moves, with a derived modifier translating in-between the two. Unfortunately, this makes it hard to, say, use standard 3d6 ability score arrays in Dungeon World (characters come out a little too wimpy, on average, and it means that there's no meaningful difference between Strength 9 and Strength 12).
This got me thinking: in what other ways can these two die mechanics cross-pollinate?
So, finally, I had a rather bizarre thought, and ran the numbers to check how it plays out. It sure does work out! There may be other uses for this little coincidental correspondence, but my first thought is that it allows effortless conversion of AW moves to D&D. (And could even be used without your D&D players catching on, if they're suspicious of such things for some odd reason.) You could play "stealth Dungeon World" (or whatever) with a group of D&D players, without having them realize that you're actually using a different mechanic, because you're still using D&D stats and your basic mechanic consists of rolling d20 ability score checks. You're using DW moves when you want to, but it still smells
like normal D&D.
That's one possible application.
Here it is:
D&D and AW Dice Babies
The mechanic works as follows:
You have ability scores in the 3-18 range, with an average score around 10, and most scores falling within the 8-13 range. Unusual abilities might be rated as low as 3-6, or as high as 15-18. You know, D&D baseline, nothing new here.
To make an ability check, roll 2d20, and compare each die to the ability score (a roll of the score or lower is a success):
* If both fail, you have a miss, or a total failure. (6 or less)
* If one succeeds and the other fails, you have a partial success. (7-9)
* If both succeed, you have a full success. (10+)
The cool thing here is that the odds match up very well, within a few percentage points in most cases:
Ability Score | AW Stat Value
3 | -2
5 | -1
7-8 | 0
10 | +1
12-13 | +2
15 | +3
17-18 | +4
So a "typical" ability score is 8-13 (between 0 and +2), while extreme scores are like a -1/-2, or +3/+4. (-2 is the lowest stat AW can accomodate before a full success becomes impossible, and +4 is the highest stat AW can accommodate before failure becomes impossible. The range matches quite well here.)
The "center point" of an AW roll sits at +1 (smack dab in the middle of the three outcomes); here it sits at 10, in the middle of the ability score scale.
You can have fun rolling the dice one at a time, if you like, with some extra narration or drama in-between, or just roll both at once, AW-style.
Rolling 3d6 for stats produces results just a touch more powerful than standard DW characters, pretty close to standard AW characters. For example (actually rolling for this, hang on...):
Corresponds to roughly:
CON +2 (and inching towards +3)
A very reasonable stat array for a character using AW moves, which tend to work best in the 0 to +2 range.
Here's another comparison (rolling randomly once more):
Corresponds roughly to:
hard +0.5 (or so)
AW characters tend to have stat arrays which add up to +3, and this was a lower-than-average set of rolls, so this is exactly in the right ballpark.
(But remember that under these rules that last character does have different odds for cool and weird, even though they're both roughly like rolling+0 in AW: this character is as much weirder than she is cool as she is harder than she is weird.)
So, if you want to import, say, 3d6-in-order stat generation to an AW hack (World of Dungeons, perhaps?), now you can do it. Roll your six stats, then use ability score checks throughout the game, for a new form of "Primitive D&D".
Or if you're running a game D&D and you wish you could use that "Parley" or "Perilous Journeys" (or whatever) move from Dungeon World just about now, say something like:
"Ok, you're going to need to roll a Charisma check. If you succeed, you're almost there, a second roll will confirm it. If you fail, you're facing disaster, but a second roll can save your bacon."
Two successes? Give them a 10+ result. Only one? It's a partial success, like a 7-9. Both fail? Make a hard move.
It still looks familiar enough to a hardened D&D player, though: it feels like a D&D mechanic, familiar and in line aesthetically with other types of rolls.
Using the Parley move as a guide, you could handle a negotiation like this, for example:
"This negotiation will take two Charisma checks. Roll the first [...]"
"Okay, you succeeded. That means they're going to agree to your plan. Roll again to see if they want some serious concessions from you in return before they do what you ask, however."
"You failed. Ooh, that's not good: that means they're probably going to expect some concessions from you even if you win them over. Roll again to see if you can get them to agree to the plan despite their rather entrenched position."
Same results as a DW Parley, but couched in D&D vocabulary, in an old-school accent any Dungeon Master from 1974 would consider entirely familiar.
Want to make an AW hack with more fine gradations in ability? (Here you've gone from about six or seven tiers (-2 to +3 or +4) to fifteen (from 3 to 18). Have at it. What was a +1 before is roughly +2.5 now, so you can have a magic bow which gives you a +1 to Volley or a set of binoculars which give you a +2 to read a sitch or whatever.
(I think that AW doesn't need this, of course, but maybe some hypothetical hack you're working on does.)
If nothing else, we now have an easy to play World of Dungeons with standard 3d6 stats - it'll "look" just like D&D, if that's a nostalgia thing you're aiming for with those old blue character sheets. Not +1 Wisdom and 0 Strength, but Strength 9 and Wisdom 13, rolled on 3d6... but the resolution and moves still work the same way.
This is also an effortless to import tiered resolution or directly port AW/DW moves, should you need them, into any D&D game. Any AW or DW move, you now have an effortless conversion point.