Tuesday, December 16, 2008

RPG Design Journal Part 2: The Core Mechanic

So way, wayyy back in April I posted Part 1 of the Design Journal, where I "set the stage" for my vague thoughts on RPG system development. A lot of time and thought has passed regarding this idea of mine, and I've chipped away a little at what I call, for better or for worse, the Tankards & Broadswords RPG. Not especially original, I know, but whatcha gonna do, right?

Anyhow, one thing that I want to hammer down before anything else is the Core Mechanic. I must admit that I am a fan of having One Core Mechanic in a system. That doesn't mean that there won't be the occasional odd roll here or there, so I guess I'm not a Core Mechanic purist, but I like having a system where, when explaining it to a new player for the first time, there's really just one core system idea you need to nail down, like "roll this d20 and get a high number" or "roll these percentile dice and hope you roll low". Basic Roleplaying does a good job of this. They have one standard percentile mechanic, but the rules aren't above asking for a random 1-10 roll or 1-6 roll now and then to determine something that doesn't need the granularity of a percentile roll.

So with that in mind, here's my Core Mechanic. I think it's relatively easy to pick up, quick, requires essentially no math, and is more or less generic enough to be used as a "Core" determination mechanic. To quote my current rules draft:

The High Roll Mechanic
The T&B RPG uses one standard mechanic for determining the outcome of most gameplay decisions - the High Roll. Whenever a character has to make a skill roll, the Player rolls a number of six-sided dice equal to the character's skill rating. The result of the throw, from highest number to lowest, is then compared to an opposing die roll - representing either an attempt by another character to prevent the action, or simply the vagaries of chance and circumstance getting in the way. Whichever throw has the "High Roll" - the highest die unmatched by a die on the opposing side - is the winner.
For example. Two characters are battling each other. The attacker makes a roll with his Melee skill of 4, rolling four dice - 5, 4, 2, 1. The defender makes a roll with his Defense skill of 3, rolling three dice - 5, 4, and 4. The first two dice match up and cancel each other out, but the first unmatched pair of dice - the attacker's 2 and the defender's 4 - determine the result. In this case, the defender wins with a Balance (remainder) of 2. The attacker's 1 is immaterial and isn't considered in the results.
Keep in mind that the number of dice rolled and the overall result has no bearing on how well an action was performed - all that matters is the result of the highest unmatched die - the High Roll. If one character rolls six dice and gets 4, 4, 3, 3, 3, and 2, and an opposing character rolls a single die and gets a 5, the 5 wins out. None of the other dice the first character rolled have any bearing on the outcome - only the High Roll matters.

The Rule of 6
Although there are only results from 1 to 6 on the dice used in the skill rolls, a High Roll can go above 6 if there is more than one 6 rolled in a single throw. For every additional 6 rolled in a single throw, the High Roll is raised by 1. So if a character rolls five dice and gets 6, 6, 6, 4, and 2, the High Roll is an 8; 6 + 1 + 1 for the two additional sixes.
Furthermore, if every die rolled in a skill test is a 6, the player is allowed to roll an additional die. If THAT die is a 6, another additional die may be rolled, and so on and so forth. This allows for a (vanishingly small) chance that the High Roll can have any result, so even a pretty incompetent character can produce a (very lucky) High Roll of 7 or more.

The "0d" Rule
Characters who have no dice in a particular skill can still try and make a skill roll. The player rolls 1d, and subtracts 1 from the result. While this doesn't seem like a big difference compared to someone with 1d in a skill, keep in mind that the -1 modifier means the 0d skill doesn't benefit from the "Rule of 6". Furthermore, even if there is a skill modifier (due to circumstances, magic, equipment - whatever) that raises the result so the roll is a "6", a 0d skill cannot ever make use of the "Rule of 6".

And there we go. This would be the basic task-resolution mechanic for the system. There will be the occasional "roll 1d/2d and look here", and damage is done using a straight die roll, but in terms of task resolution, the "High Roll" is it.

Opinions? Comments? Questions?


jamused said...

Why that mechanic? My sense is that it's astonishingly hard to get a quick feel for how likely you are to succeed for the various combinations of dice. Does it serve a particular purpose?

Badelaire said...


1. I wanted something that used multiple dice. I.e., the better you were, the more dice you tossed. D6s are (typically) the die of choice in this regard, Storyteller system not withstanding.

2. I wanted something kind of unusual, but still easy to resolve. D6 system used "roll and add 'em up", and I didn't want that much math. I toyed with a "roll the dice and on a 4+ it's a 'success'" kind of like Storyteller, but felt that this was a little too bland as well. The Silhouette RPG system uses something pretty close to this mechanic (roll Xd dice, highest wins, multiple 6's add to the total), but with contested rolls, you're going to get a lot of ties if your dice pools are relatively small. The way my mechanic works, it's sort of like playing poker with dice - instead of a high card you have the High Roll, and multiple 6's give you a even better hand. But you can look at a pair of dice rolls and tell in just s second who won the contest.

3. In terms of the "how likely you are to succeed for the various combinations of dice" - that's exactly what I'm trying to avoid. I don't want players "doing the math" and trying to hack the system. The better you are, the more dice you roll, the better the chances you'll beat out someone with fewer dice than you. Boom. That's all you need to know. Life for your adventuring PC is about taking risks, and you don't always know how risky something is going to be until you give it a go.

4. Now, you CAN do the math on these numbers, and perhaps I'll attach as an appendix to the rules a few charts giving percentile chances of how Xd performs vs. Yd and the average balances you'll come up with. That is, if I don't put myself to sleep every time I attempt it.

Jonathan said...

To be honest - the statistics of the above system would favor "ties" at lower levels of play. and, at higher levels, rolling piles of dice - which then all have to be compared to another pile of dice (your opponents) just to resolve a granular action of the game seems cumbersome to me. While I recognize that you are trying to come up with something different, a simpler system could be envisioned that doesn't require so many dice-to-dice comparisons. If you have, for example, 5 players and a GM and combat lasts say... 5 rounds on average then you are looking at a minimum of 25 - 30 dice pool rolls per combat (just for the players). I would prefer, personally, a faster system for resolving mechanics. Just my 2¢.

jamused said...

Fair enough. It's pretty much the opposite of what I want in a core mechanic; I strongly prefer systems where if the GM says "You have to beat 5 to jump across the pit" I can have a good sense of whether my roll is going to be enough or I'll plunge to my doom instead of having to just try it and see. Different strokes for different folks.

Badelaire said...

- Jamused,

As a GM I'd probably tell my player how many dice will oppose them, representing the degree of difficulty. In other words, you're rolling 3 dice for Athletics, I'm opposing that with two dice. You're more likely to get the High Roll than I am. If you're rolling 4 dice, you're even more likely.

But I guess you mean, being able to say to yourself "OK, I've got an 80% chance of making this jump." Well...who can actually do that?

I mean, wow often do we find ourselves (outside of a role-playing game) able to actually quantify our odds beyond "I've got a good chance of doing this" or "I'll probably never pull it off"?

I'm guessing, not too often. In that regard, I like the idea that the mechanic helps set aside "playing the odds".

jamused said...

We almost never quantify it because our brains aren't designed to work that way...but we have very strong "gut" senses of whether something is dangerous to attempt. The dice mechanic is (IMO) designed to replace that visceral sense with something that the player can evaluate in its place. In your system players may eventually develop a "feel" for how often their four dice will beat three, and so whether the attempt is worth it or suicide, but the more opaque you make it the harder it will be for them and for you as GM to know what's reasonable, even at the crudest level, and the longer it will take before they're used to it. The players aren't the only ones who have to make those judgements on the fly. Suppose a character is designed to be an excellent race-car driver, and has 6 dice in Driving. He wants to negotiate a hair-pin turn on a mountain road at high speed. You and he both think that's reasonable for someone of his skill, though by no means certain. How many dice will you have him roll against? How much more likely is he to crash and burn if you made it one die more or he had one point less?

Badelaire said...

- Jonathan,

Regarding the "ties"...I've got people doing some math right now, but I've tried dicing it out, and I very rarely get ties once you get to around 3 dice (which is the low side of average for skills dice - the pool goes to about 6d for "normal" PCs). I mean, this'd only happen 16% of the time for 1d vs. 1d, and it just quickly goes downhill from there. Now, there's not going to be a LOT of variance - you'll have a lot of "remainder of 1" situations, but that's no tie.

Regarding the rest...I guess it's all a matter of perspective. Do you think that's more complicated than, say, GURPS, or D20, or BRP, or Classic D6, or Storyteller? After a little practice I can very, very quickly glance at two small piles of dice and see which die is the High Roll, and then your Balance is the difference between the two. But some people just prefer non-dicepool mechanics over dicepool mechanics. I've played Warhammer 40K for years, so I can glance at a pile of 20-40 dice and pick apart the "hits" or "wounds" very quickly - dice pools of 1-6 d6s don't make me so much as blink.

Badelaire said...

Well guys, after the comments here and some more dialogue on this end between some of my people, I think you're right - the mecnaic (while I still like it) is just not straightforward enough for what should be a very straightforward game system. I'll put up another post tomorrow or thereabouts with some more ideas.

Thanks very much for your input - it definitely helps to have additional brainpower working on these ideas.

MJ Harnish said...

Your mechanic, which is a dice pool, is similar to the one used in Cold City. It, however, uses D10's which give you a lot more spread of results and thus ties are less frequent. Cold City also looks at the number of successes (dice that beat your opponent's) to determine a level of success.

Your "all 6's" rule is very confusing and just adds a lot of unnecessary complexity.

In terms of your poker analogy, I don't see that element at all. If you really want a system that feels like poker, including the seeing & raising, strategy, take a look at the system used in Dogs in the Vineyard (or the Princes Kingdom which is somewhat similar in that it sticks to a single die size)

Brisbe said...

I'd like to point out that there's one bit of rule in there that's just fluff--and doesn't actually change anything. The 'add 1 to a 6' part of the rule. It doesn't matter that you add 2 to a 6 if you roll 3 6s, giving you an 8 6 6.../because you rolled 3 6s/. Your 3 6s will beat someone else's 2 6s and a 5, just as your 3 5s will beat someone else's 2 5s and a 4.