Game Design: Good average chances of success for all situations?

[GMMichael]

I mean, look at baseball. From the hitter's perspective, consistently succeeding at getting on base 1/3 of the time is pretty damn good. But that also means a pitcher's expected success rate in not allowing the batter to get on base is, ideally, higher than 2/3.

That's why I don't play baseball. You spend most of your time in the field watching other players failing to succeed.

Wait.

I think I just described D&D...

 

[aramis erak]

For me, the most intuitive is the DPG-CT, 2300 AD, and MegaTraveller task system It's called the DGP-CT as it was introduced in Digest Group Publications' supplements for Classic Traveller; the MegaTraveller system has some additional nuances, but is the same fundamental math. GDW (makers of CT, MT, and 2300) changed the math a touch by the die swap; the odds are actually better for harder tasks under 2300.

I'll note that I intuited the baseline pretty early in... like the first session I used it.
Note that all three games define skill of 1 as a level employable in trades or as ship crewmen; Doctors and Lawyers are defined as level 3... and certain CT programming tasks need Computers 8... which I've only seen in MT...

The labels are built for the average NPC... CT/MT Stat 7 or 8 (providing +1), skill 1; 2300 stat 10-11 (providing +2), skill 1.
CT and MT, it's 2d6, 2300 is 1d10.
This gives Min/Median/Max of CT/MT 4/9/14, 2300 of 3/8.5/13
Rushing shifts up a difficulty and reduces time; caution shifts down difficulty but doubles time.
Simple 3+ Given the minimum roll, the PC cannot fail.
Routine 7+Usually doable (CT/MT Nat 5+ 5/6 for 83.333% chance; 2300 nat 4+ for 70%); extra time makes it automatic.
Difficult 11+ doable most of the time if you can do it cautiously, risky otherwise; rushing is impossible. (CT/MT nat 9+, `27%; 2300 nat 8+, for 30%)
Formidable 15+ Requires taking extra time or having better than the base 1 rank employable skill and/or attribute... (CT/MT max 14 is below the needed; 2300 max 13 is below the requirement) Note that higher attribute (10+) can hit this rarely (3%); in 2300, this requires professional (as in, Graduate School level) skills or experienced employable skill and high attribute.
Impossible 19+ - the average guy working in field cannot do this, not even by extra time. The MT max allowed die roll gives this a slim chance in both.
I like this kind of analysis; I don't care for the CT/MT using att/5, as it's a 2d6 att; 2300 using att/5 is much better for me, as it's 4d6-4 for atts..., so I up the CT/MT TN's by 1, but use att/3 instead of att/4

 

[Voadam]

For me the sweet spot is generally an at the table baseline of 3/4 success. Generally as a DM and a player I prefer succeeding more often with a chance of failure over big chances of failure where either nothing happens in the story (a missed attack) or there is an actual incompetency.

With too big a chance of failure the incentive is to avoid the mechanics and shift to narratively dealing with stuff where you can, but for something like D&D combat I generally enjoy doing out the mechanical stuff as part of the game.

The tone I enjoy is a bit more action movie or superhero/Conan comic book level of action and competency.

I find the players generally provide enough bad choices and bad luck on rolls that I do not want the system to grind them down as well as a baseline.

 

[payn]

I'm liking Travellers flat progression and 2D6 base more and more. Though, I will say I am a fan of bounded accuracy in D&D. Seems not only the deigning is easier this way, but also easier to understand and feel as a player/GM.

 

[Pedantic]

I think it's as or more important to consider the player build/resource side. What is the set of spreads a player can access, and what is the resource cost of being good at something?

The incentives to specialize hinges on a pretty small window, where the marginal improvement at a given check need to be significantly higher, or the resource cost needs to be quite cheap. Pushing either of those too far and player conservatism will favor generalists.

 

[LegendaryAdventureStudios]

Hey, thought I could contribute for how Array of Champions has it.

First, some explanation about the system itself. Characters have what I would define as 'Strong, Normal and Weak' statistics. Level 1 Strong is 100 in the statistic, 85 is normal and 70 is weak. It's a D100 system where you subtract an enemies defence from your offence to find the DC (so if your Weapon Attack of 100 is targeting a Physical Defence of 35 you need a 65 to hit). It's worth noting the player also rolls for defensive rolls, not the GM - taking the enemy offensive statistic and reducing it from their defence (so a fireball might involve subtracting an enemies Supernatural Attack from your AOE Defence to find the target DC)

In practice when facing a same level enemy the following math occurs

Strong vs. Strong - 65% chance of success
Strong vs Normal - 80% chance of success
Strong vs Weak - 95% chance of success

Normal vs. Strong 50% chance of success
Normal vs Normal - 65% chance of success
Normal vs. Weak - 80% chance of success

Weak vs. Strong - 35% chance of success
Weak vs. normal 50% chance of success
Weak vs. Weak 65% chance of success

Now this math does get skewed - your level up progression is going to increase your statistics above the prescribed math curve (a "min maxed" character could alter the math to get +20% in ALL strong statistic chances at the level cap [20], (meaning they, on paper at least auto hit when targeting normal or weak)

Where things get more interesting math-wise is how the tactical application of buffs and debuffs from both sides can skew this math to create guaranteed successes or ruin solid chances into becoming near impossible. Over-committing to creating either situation can leave you vulnerable in a different area too!

Now do keep in mind the tone is Heroic Fantasy with Void Knights slashing enemies 300ft away, Heralds running at high enough speeds to exit combat by running to the future and suddenly having two of them present at once and other nonsense. Hence the skew towards players succeeding - besides in a system where players make every roll, they're bound to fail some.

 

[aramis erak]

I'm liking Travellers flat progression and 2D6 base more and more. Though, I will say I am a fan of bounded accuracy in D&D. Seems not only the deigning is easier this way, but also easier to understand and feel as a player/GM.

MegaTraveller had bounded accuracy in 1987... (die roll mod limit +8)

 

[Kannik]

(Apologies in advance for the thread necro.) From what I've experienced, for an adventurous style game a 66%-75% chance of success for something is in the character's wheelhouse seems to be the sweet spot.

 

[aramis erak]

When designing new systems or homebrewing existing ones, one of the areas where I still often question both my experience and my gut feelings are the target values for average chances of success on a given roll.

My preferred metric comes from the DGP Task System (used in DGP's supplements for Classic Traveller, then later adapted officially for GDW's 2300 and MegaTraveller)
The default labels are based upon attribute 7 and skill 1, for a net DM+2. Max allowed from atts and skills is +8. (Bounded accuracy! in 1985.) Extra Time is effectively a +4, hasty is a -4 (it's actually as a label shift, but the math is the same.
The roll is 2d6 plus the above.
Maximum DM from atts and skill is +8. Minimum is -4 (att <5 and skill not taken)

		Guy Normal	Miss Max
Label	Base TN	DM+2	DM+8
Simple	3+	36/36	36/36
Routine	7+	30/36	36/36
Difficult	11+	10/36	35/36
Formidable	15+	0/36	21/36
Impossible	19+	0/36	3/36

Note that Normal cannot succeed on Impossible; extra time makes it equal formidable, still out of his reach. Extra time on routine tasks makes them equal to easy, and thus automatic.
Max autosucceeds on hasty simple tasks, most of the time (35/36) on hasty routine tasks.difficult tasks are also automatic with extra time for Max... and almost automatic for difficult at normal pace. Max is even better than 50% on difficult tasks when hurrying. Even the impossible for the starting pro tasks can, with extra time, be accomplished more than 50% of the time.
In play, I added another level: Plaid (inspired by Spaceballs and a PC with a couple +8 combinations)... extra time required and a 1/12 chance... gives even Mr. Scott pause. I also renamed Impossible to "Nearly Impossible" for the pedants in my group.

 

[dragoner]

I do the 2/3rds thing, liking to think that every time the players roll they should have 2/3rds chance of success, however it doesn't always work out that way.