What do you think of this system? D12 based roll under

[SpoDaddy]

Roll XD12, X being the attribute number  Attributes are rated from 1-7.  Skills are rated from 2-11, every die that rolls equal to or under the skill number is kept.  Kept dice are then added together.  Suggestions, comments, questions?  Is this too addition-heavy?

[Jasper]

Well...why not try it and find out?  You're asking about handling time and maybe rolling asthetics, but there's no absolute cut-off on what's "too long," so I don't think anyone here can really tell you what's acceptable -- it's your call.

That said, assuming a middle of the road attribute of 4 and a skill of 6, you're going to be counting up 1.7 dice on average.  That's pretty trivial. The actual rolling and sorting of which dice to count is also minor.  If you're imagining much higher stats, it could obviously take longer, but even at 7 and 12, it's quicker than some other mechanics out there.

[Jack Spencer Jr]

Let me get this straight, You roll a number of d12 equal to a stat and then numbers rolled under the appropriate skill are kept. The kept numbers are added to produce the final result.

Is there a reason to add the actual numbers rolled instead of couling these dice as a "success" and the number of successes is the final result?

[SpoDaddy]

Jack: I want the system to take skill and training directly into account more.  If the system only looked at successes, then the number of dice rolled (attributes) would be far more important than the numbers they roll under (skills).  By adding the dice, even with only 1 or 2 in an attribute you can still beat someone with 6 or 7 in that attribute regularly if your skill is that much higher since you're working with 1 or 2 huge numbers as opposed to a lot of little numbers.

[Minx]

Your system sounds interesting, but I´d have a problem figuring out target numbers. What would you have for a "normal" task?

M

[Jasper]

One thing you might want to consider is switching up the way dice are counted: instead of including those under the skill, include those that are over it.  With the roll-under method, you get a curve with very low numbers at the low end of skills.  With 4 dice, the average results are as follows, with increasing skill (including 1 and 12 for completeness):

1: 0.3
2: 1.0
3: 2.0
4: 3.3
5: 5.0
6: 7.0
7: 9.3
8: 12.0
9: 15.0
10: 18.3
11: 22.0
12: 26.0

So the difference between skill 10 and skill 11 is much bigger than the difference between 2 and 3.  If you do it the other way, rolling over, this effect is less severe.

As for the importance of skills versus attributes, below are the averages for different attributes, with a set skill of 6:

1: 1.75
2: 3.5
3: 5.25
4: 7.0
5: 8.75
6: 10.5
7: 12.25

So in this case you have a difference of 1.75 between each point of attribute, whereas in the above example, with constant attribute of 4, the difference between any point of skill is 3.17...obviously this depends on what you consider typical values, but you still might want to rethink your reasoning on that one.  Personally, I like the system, and it's one I've used in the past -- though if you don't specifically need it, other systems might be easier.

[SpoDaddy]

Minx: Based on my very early calculations, average task would be difficulty 4


Jasper: Great post.  How are you suggesting counting only the dice that roll over without rewarding lesser skill?

[SpoDaddy]

Another rule I'm thinking about using is allowing dice to explode (reroll) if they roll the exact skill number

[Lxndr]

How are you suggesting counting only the dice that roll over without rewarding lesser skill?

How would this reward lesser skill?  If you have a skill of 12 (and, since it's roll-over, that's the worst skill that could possibly exist) then, sure, if you roll all 12s, yay, you're wonderful.

But if you're going against someone who's got a skill of 11, they have TWICE the number of numbers they CAN roll, to keep.  If both of you roll all 11s, he wins and you lose.

It's already ample reward for dice that roll-over.

[Jasper]

Hi,

Yeah, as Lxndr said, you just need to consider lower skills better.

I've knocked up some graphs showing the two possibilities, so you can see how the curve changes here.  Hope that helps -- it's part of a larger die rolling guide which you might also find interesting.

[SpoDaddy]

That's what I thought you meant (lower skills are better), just wanted to make sure.  You're really great with probabilities Jasper, by any chance could you help me out with my other D12 system I'm working on?  Both systems are for the same game (a 24 inspired espionage game), I'm having trouble deciding between the 2 and I can't figure out the probabilities on the other one for the life of me.  

The goals for me in this design are

A) The system has to take level of skill into account (for example, a critical success by an expert should be better than the critical success of an amatuer)

B) The system has to have a built in way of effecting time (allowing you to subtract successful dice from your pool, for example, to lower the time the task takes).  Since the game is inspired by 24, time will be crucial.

C) The system has to give satisfying results while being relatively fast.  Hit locations, for example, are important as an agent with a gunshot wound in the left arm is more useful than an agent with a gunshot wound in the left leg.  

The system works like this so far: Attributes are a number of D12's rolled against a skill number.  If you rolled no successes and at least one 12, you botch.  Look at the highest roll that is equal to or less than the skill number.  Set that aside as your base roll.  If you rolled exactly your skill number, double the value of the roll.  Keep any other dice that rolled equal to or under the skill number.  Add 1 point to the base roll for each additional success.  If any of these additional dice rolled a 1 or your skill number exactly, count the success then reroll the die.  When you're finished, compare your final total to the target number.  You can remove successful dice in exchange for a reduction to the notional time the task takes at a rate of 10 percent per die removed.

If you could help me out with the probabilities for various rolls in this system Jasper, and give me your thoughts on it, I'd be greatly appreciative :)

[Jasper]

Hi,

My first reaction to the second method is that it's awfully complicated...you're taking highest dice, counting dice over a value, deciding whether to count a die doubly, rerolling other dice, and comparing all this to a fixed total.  If nothing else, I'd leave out the re-rolling.  This adds a lot of additional handling time, and doesn't change much: it doesn't help good people do better for instance, or serve as any other kind of differentiator; it just increases the scale that you're working on, which seems plenty big to me as it is.  

If you do leave out the re-rolling, these are some probabilities for different skills, assuming a baseline attribute of 4:

1: 0.9
2: 2.1
3: 3.4
4: 4.8
5: 6.3
6: 8.9
7: 9.5
8: 11.1
9: 12.7
10: 14.3
11: 15.6
12: 17.6
13: 14.1

As you can see, more than a linear rise.  I don't know if you'd allow a skill of 13, but you can see that it creates an odd blip, since you can roll under it, but never get the double bonus by rolling equal to it.  Here are the averages for a changing attribute with static skill of 6:

1: 2.8
2: 4.8
3: 6.5
4: 7.9
5: 9.1
6: 10.2
7: 11.2
8: 12.1

So, less than linear increase here.  Stepping from 1 to 2 attribute means more than stepping from 7 to 8.  At middle ranges (attribute 4, skill 6), the skill has more influence on the average than the attribute.  

Hope that helps.  (And BTW, as I said, this isn't a simple system.  It took my 2.8Ghz Pentium III more than a few seconds to produce the result for skill 4, attribute 8.)

[SpoDaddy]

Thanks for the feedback Jasper, I really have no clue how to handle figuring out probabilities for this :)