Your thoughts on my game mechanics

[John Blaz]

Hey everybody! Long time lurker, first time poster.

I've been tossing an idea for an RPG around for some time, a modern day tactical survival horror game. One of my goals was to have a fluid, yet somewhat realistic combat system, maybe even including rules for blood loss over time. After going through some different ideas (d20, percentile system, success rolls system) I think I've finally found one I like:

Stats and skills are rated from 1d6 to 5d6.
The skill roll is Stat + Skill, so anywhere from 2 to 10d6.
The idea is to roll many of the same number, and add the result. The result is called the Effect.
If no dice come up the same, the skill is failed.

Example 1: To climb a wall, a character rolls his Strength and Climb skill for a total of 6d6. The rolls come up 3, 4, 5, 3, 3, 3. All of the 3s are added together to get 12. 12 is the Effect of the roll.

For opposing rolls, both characters roll the relevant skills, and the defender's Effect is subtracted from the attacker's Effect.

Example 2: In a fight, PlayerA tries to strike PlayerB, who is dodging.
PlayerA rolls his attack skill (5d6) and gets 1, 2, 4, 4, 5  (taking 4s) for an Effect of 8.
PlayerB rolls his dodge skill (5d6) and gets 2, 4, 3, 2, 3 (taking only the 3s) for an Effect of 6.
PlayerB's defense Effect is subtracted from PlayerA's attack Effect, leaving PlayerA with an Effect of 2 for his attack.



Basically, I'm debating whether the Effect of a skill/ attack should translate directly into damage (so deadlier weapons would add to the final Effect) or if the Effect could be used any other way in combat, like deciding on a hit location.

Any thoughts on anything I've presented are very much appreciated.

[maov]

The system you chosen to roll with is not really the worlds easiest to figure out mathematically, but it is easy to see that all multirolls are equally likely to occur which means that the difference is going to be very wide spread. I would never use wide spread on a dice roll add to damage given that it will be extremely hard to control, normally the reason for having both hit and damage is that you even out rolls and you can balance them independent of each other (the disadvantage though is multiple rolls which slows down play). Hit location though is a very good idea you could say that:
Effective dice roll

• 6: head
• 5: body
• 4: left arm
• 3: right arm
• 2: left leg
• 1: right leg

[Selene Tan]

Hi John!

Your system reminds me of Godlike, which uses a similar dice-matching mechanic on d10s. John Kim has a short writeup of it here.

Anyway, I did a quick analysis of the probabilities. It's equally likely that a set of matches is a given value, e.g. on 3d6, it's as likely that you'll have a pair of 2's as you will a pair of 6's. Here's the chance (as percentages) of getting a given number of matches on nd6. A "0" indicates that the probability is 0 when rounded to 2 decimal places. A . (period) means that it's impossible to get that many matches on that many dice.

Code Select Expand


Dice Number of matches
0 1 2 3 4 5 6 7 8 9 10
2d6 69.44 27.78 2.78 . . . . . . . .
3d6 57.87 34.72 6.94 0.46 . . . . . . .
4d6 48.23 38.58 11.57 1.54 0.08 . . . . . .
5d6 40.19 40.19 16.08 3.22 0.32 0.01 . . . . .
6d6 33.49 40.19 20.09 5.36 0.80 0.06 0 . . . .
7d6 27.91 39.07 23.44 7.81 1.56 0.19 0.01 0 . . .
8d6 23.26 37.21 26.05 10.42 2.60 0.42 0.04 0 0 . .
9d6 19.38 34.89 27.91 13.02 3.91 0.78 0.10 0.01 0 0 .
10d6 16.15 32.30 29.07 15.50 5.43 1.30 0.22 0.02 0 0 0


[maov]

Ehm i think you moved the table with dice wrong or something because getting a match with two dice should be 6/36 * 100, given that the set of matches = {(1,1),(2,2),(3,3),(4,4),(5,5),(6,6)}, also what is a 0 match a dice will always match itself. Or is it the probability for getting a specific match/roll??

[Selene Tan]

The table is for getting a specific match, e.g. the probability of a pair of 6s.

[Vulpinoid]

Thanks for the table Selene, it confirms something in my head about this system.

...but I've got my own query about it.

At my first glance, the system seemed to be heavily stacked toward failure for characters with low ranking skill/attribute combinations.

If no dice come up the same, the skill is failed.

1 die can never match because there are no other dice to match with.

2 dice mean you've only got a 1 in 6 chance of them matching one another, and therefore a 5 in 6 chance of an auto-fail.

Your calculations cover the chances of gaining one or more matches when more dice are involved. I had suspected that you'd need a decent number of dice to accumulate a better chance at success than failure.

It threw me at first because I tried to work out how 2 dice could generate two matches...surely a single die only has one other die it can match against in this situation...then I re-read the posts, and I see that you've basically included a virtual die for cross referencing purposes.

If we forget comparisons to a specific number, then I've just done some analysis to determine that for getting an 2 dice to match on 3d6 there are 60 chances in 216 (27.78%). Getting three dice to match has 6 chances in 216 (2.78%). The only problem is that you've derived them from a single value rather than calculating the odds across the board. You'll note that these two figures match the top line of your table.

I haven't done the complete math, but I'm guessing that for your table to work against all possible matches, you'd just have to drop everything down by a line.

Code Select Expand

Dice Number of matches
0 1 2 3 4 5 6 7 8 9 10
3d6 69.44 27.78 2.78 . . . . . . . .
4d6 57.87 34.72 6.94 0.46 . . . . . . .
5d6 48.23 38.58 11.57 1.54 0.08 . . . . . .
6d6 40.19 40.19 16.08 3.22 0.32 0.01 . . . . .
7d6 33.49 40.19 20.09 5.36 0.80 0.06 0 . . . .
8d6 27.91 39.07 23.44 7.81 1.56 0.19 0.01 0 . . .
9d6 23.26 37.21 26.05 10.42 2.60 0.42 0.04 0 0 . .
10d6 19.38 34.89 27.91 13.02 3.91 0.78 0.10 0.01 0 0 .


What this version of the table doesn't take into account is the fact that four dice could roll two pairs, five dice could roll two pairs or a "full house"...But it does give a definitive value for a players chances of an auto-fail [no matches]. And you can see that someone needs at least 5 dice in their hand for a better than average chance of success.

With a scale of combined skills/attributes ranging from 2 to 10, this is just below the midpoint...there's going to be a lot of auto failures in this system.

This might be desired, but maybe not.

If a high failure rate is not desired, there are a few ways to remedy this...such as including some kind of feature that allows a player to modify their die results (spend a willpower to increase or decrease any die face by 1...or maybe you're just so good at something that you can modify a die face by 1 at any time when your focal skill is involved).

V

[John Blaz]

Thank you everyone for your input, I hadn't realized just how likely failure would occur when limiting the dice to 10d6. I'd rather not have a ridiculous amount of dice being rolled everytime a skill check is needed, so simply increasing the maximum dice pool to 20 (10 for stats and 10 for skills) may be a bit much.

But using the program SmallRoller, I've found the percentage of success for the proposed system is as follows:
For the dice to have at least 2 matching faces (which counts as a successful roll)

2d6   2.8%
3d6   7.4%
4d6   13.9%
5d6   19.6%
6d6   26.3%
7d6   33%
8d6   39.5%
9d6   45.7%
10d6  51.6%

If failure is this likely when using d6s, wouldn't failure in Godlike and similar systems that use the d10 for this be almost guaranteed at most times?
It seems I'll need to ponder this a bit more.

[Selene Tan]

Hey, so I realized that the thing I calculated probabilities for was not actually anything useful. This table is what you want:

Code Select Expand


number of matches
dice 0 2 3 4 5 6 7 8 9 10
2d6 83.33 16.67 . . . . . . . .
3d6 55.56 41.67 2.78 . . . . . . .
4d6 27.78 62.50 9.26 0.46 . . . . . .
5d6 9.26 69.44 19.29 1.93 0.08 . . . . .
6d6 1.54 61.73 31.51 4.82 0.39 0.01 . . . .
7d6 . 45.91 43.51 9.38 1.13 0.08 0 . . .
8d6 . 29.26 52.41 15.57 2.50 0.25 0.01 0 . .
9d6 . 15.75 55.85 23.03 4.69 0.63 0.05 0 0 .
10d6 . 6.75 52.93 31.05 7.81 1.30 0.15 0.01 0 0


Okay, I can't get the tabs to line up properly now... Here is an Excel file that holds the same data, and also some charts.

Some notes:

• It's impossible to fail (have no matches, not even a pair) with more than 6 dice.
• You'll basically never see 7 or more matches,even on 10d6

[John Blaz]

I'm honestly having a bit of trouble understanding this Excel graph here, but I do appreciate the effort. So is this a feasible system? I'd like for skilled characters to be able to have some consistency with their rolls so that higher skills mean more regular successes. If Godlike uses this with d10s, it should work relatively well with d6s, right?

[vgunn]

John,

I think there is a lot of potential here. However, I do also agree with the previous posters that failure under the rules as presented will be quite high without some other option. Here is some information on how the the One-Roll Engine (ORE) found in Godlike and Wild Talents.

Quote:

O.R.E. system uses a dice pool of d10s equal to the character's Stat and Skill similar to that used by Storyteller system, but the method to determine success is different. In the O.R.E. system, success is determined by die result matches, such as a pair of 8s. The Width of a roll, the number of matching dice, determines the speed (and damage, if in combat) of a roll, while the Height of a roll, the face up result on the matched dice, determines how successful an action was and location of a hit in combat. Shorthand notation for writing results is Width x Height, so a pair of 8s would be written 2x8 and three 2s would be written, 3x2.

Two special types of dice also come from Talent Powers, Hard Dice, which are considered to always have a value of 10, and Wiggle Dice, which the player can assign any die result to after the roll. The shorthand notation for Hard Dice is hd and Wiggle Dice is wd, so a Dice pool of six regular dice, two Hard Dice and one Wiggle Die would be noted 6d+2hd+1wd.

-- Wikipedia

http://en.wikipedia.org/wiki/One-Roll_Engine

Using d6 in the ORE system was tested however it proved to be too compressed. It was too easy to succeed at everything all the time. Using Stat+Skill the levels needed to be something like 1 = rank beginner, 2 = expert and 3 = master -- otherwise, players with 7d pools would never fail at anything.

Your system, while similar is different enough to still use d6. But you will need to have something else in conjunction with the base mechanic to reduce the high chance of failure.

You could do something like Endurance. In this case a player can burn a stat point to roll another d6 in case of failure. The stat is temporarily reduced, however it will refresh at a later time. Or burn Stat point(s) to alter one of the d6 up or down (example:  two d6 are rolled 2, 4 -- the player can burn 2 Stat points to get the dice to match. In this case bring the 2 up to 4 so the Effect would be . A possible way to simulate fatigue.

Hope this helps!

I would make tests such as Damage/Toughness and Fear go against Stat only (Endurance simulating Mental, Physical or Spiritual fatigue), therefore burning Stat Point(s) could prove risky use without careful thought from the player. Is the Effort worth the Endurance lost?

Hope this helps